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  • 1.
    Abramson, Nils H.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Elliptic visualizing optical resolution and kinetic energy2017Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, nr 5, s. 1413-1416Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diffraction limited resolution as introduced by Abbe is well established, but interference limited resolution was not well known until holographic interferometry was introduced. The holodiagram is used to simplify holography and in a new way visualize the distribution, ratio, and relation among resolutions of different optical techniques, including relativistic phenomena. Resolution, when measured by optical methods based on the number of wavelengths of light, is defined in the following as the minimum distance between resolvable points, or the largest object needed to be resolved. Everywhere in the diagram this resolution is represented by two orthogonal diagonals of rhombs.

  • 2.
    Abramson, Nils H.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Mätteknik och optik.
    Holodiagram: elliptic visualizing interferometry, relativity, and light-in-flight2014Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, nr 11, s. 2398-2404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In holographic interferometry, there is usually a static distance separating the point of illumination and the point of observation. In Special Relativity, this separation is dynamic and is caused by the velocity of the observer. The corrections needed to compensate for these separations are similar in the two fields. We use the ellipsoids of the holodiagram for measurement and in a graphic way to explain and evaluate optical resolution, gated viewing, radar, holography, three-dimensional interferometry, Special Relativity, and light-in-flight recordings. Lorentz contraction together with time dilation is explained as the result of the eccentricity of the measuring ellipsoid, caused by its velocity. The extremely thin ellipsoid of the very first light appears as a beam aimed directly at the observer, which might explain the wave or ray duality of light and entanglement. Finally, we introduce the concept of ellipsoids of observation.

  • 3.
    Abramson, Nils H.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Mätteknik och optik.
    Optical resolution and the duality of light2008Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, nr 19, s. D1-D5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For 15 years, lensless microscopes have been constructed based on the use of holography, a digital CCD detector, and a computer for image reconstruction by use of, e.g., Fourier transformation. Thus, no lens is involved and therefore the conventional resolution limit of half the wavelength no longer applies. Instead of being limited by the wavelength, the resolution is in this case limited by how exact one can measure the phases of the light. It is remarkable that the interference-limited resolution is approximately 0.01X, whereas the diffraction-limited resolution is only of the order of 0.5X. It is my hope that by combining these two techniques it will be possible to increase the magnification in optical systems by at least an order of magnitude. The calculations at so indicate that information does not necessarily decrease with distance.

  • 4. Baxter, G. W.
    et al.
    Schlup, P.
    McKinnie, I. T.
    Hellstrom, J.
    Laurell, Fredrik
    KTH, Tidigare Institutioner, Fysik.
    Single-mode near-infrared optical parametric oscillator amplifier based on periodically poled KTiOPO42001Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 40, nr 36, s. 6659-6662Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A singly resonant, single-axial-mode, optical parametric oscillator (OPO) based on periodically poled KTiOPO4 (PPKTP) is reported. Signal (1.68 mum) and idler (2.90 mum) optical bandwidths have been narrowed to < 400 MHz by use of a diffraction grating at grazing incidence. The OPO generates 370 muJ of signal radiation when pumped by 3.1 mJ of 1.064-mum radiation. We implemented a single-pass PPKTP amplifier to yield 2.15-mJ signal and 1.17-mJ idler radiation without broadening the spectral bandwidths.

  • 5.
    Beckman, Claes
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Disputing Viking navigation by polarized skylight.1994Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, nr 21, s. 4754-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The widely held notion that the Vikings utilized polarization of skylight on overcast days for navigational purposes is demonstrated to have no scientific basis. The use of polarized skylight for navigation under partly cloudfree skies should be treated with caution and skepticism.

  • 6.
    Beckman, Claes
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Intraocular light scattering in vision, artistic painting, and photography.1994Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 33, nr 21, s. 4749-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Light scattering in the eye is reviewed, and its influence on vision is discussed in some detail. Isotropic scattering and formation of halos around point sources are described with reference to theory and experiments. Artists usually take intraocularly scattered light into account when painting natural scenes. A method to achieve similar effects in photography by the use of diffraction filters in front of the camera lens is demonstrated. A number of photos that illustrate the effects of such filters are shown.

  • 7.
    Beckman, Claes
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, KTH Center för Trådlösa System, Wireless@kth. KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Optical properties of diffractive, bifocal, intraocular lenses.1992Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 31, nr 13, s. 2377-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The resolution of diffractive, bifocal, intraocular lenses was studied with regard to pupil displacement and diameter size through computer simulations, bench measurements, and patient vision-acuity measurements. Good agreement was obtained between these three methods of investigation. In particular, we find that pupil displacements of the order of 1 mm reduce the resolution considerably for these lenses.

  • 8.
    Bjurshagen, Stefan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Hellström, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pujol, Maria
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Aguiló, Magdalena
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Díaz, Francesc
    Fisica I Cristal-Lografia de Materials (FiCMA), Universitat Rovira I Virgili, Spain.
    Fluorescence dynamics and rate equations analysis in Er3+,Yb3+ doped double tungstates2006Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 45, nr 19, s. 4715-4725Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fluorescence dynamics in Er3+ and Yb3+ doped KGd(WO4)(2) and KY(WO4)(2) has been investigated. Lifetimes have been measured for the Yb(F-2(5/2)), Er(I-4(13/2)), and Er(S-4(3/2)) levels around 1, 1.5, and 0.55 mu m, respectively. The Yb(F-2(5/2)) lifetimes show a decreasing trend toward the limiting Er(I-4(11/2)) lifetime with increasing Er-to-Yb concentration ratio, whereas the Er(I-4(13/2)) lifetimes are mostly unaffected by the doping concentrations. A rate equation analysis has been performed to explain the observed behavior and gain is calculated for a continuous-wave laser at 1.53 mu m to find the optimum doping concentrations for high gain.

  • 9.
    Bjurshagen, Stefan
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Koch, R.
    Acreo AB, Kista.
    Modeling of energy-transfer upconversion and thermal effects in end-pumped quasi-three-level lasers2004Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, nr 24, s. 4735-4767Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An analytical model of cw quasi-three-level lasers that includes the influence of energy-transfer upconversion (ETU) has been developed. The results of the general output modeling were applied to a laser with Gaussian beams, and rigorous numerical calculations have been made to study the influence of ETU on threshold, output power, spatial distribution of population-inversion density, and fractional thermal loading. The model was applied to a laser operating at 946 nm in Nd:YAG, where the dependence of laser-beam size on laser performance was investigated in particular. A simple model for the degradation of laser-beam quality from a transversally varying saturated gain is proposed that is in good agreement with measurements of the laser in a plane-plane cavity.

  • 10.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Lorentzian spatial intensity distribution in one-photon fluorescence correlation spectroscopy2009Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 48, nr 31, s. 6050-6058Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The theory of autocorrelation-function evaluation in fluorescence correlation spectroscopy is applied to a Lorentzian intensity distribution. An analytical solution to the autocorrelation function for diffusion is deduced for this spatial distribution. Experimental investigation of the distribution is performed using an enlarged detector aperture in a standard confocal setup. The data from the experiment are fitted to the derived autocorrelation function, and a reasonable estimate of the spatial distribution is provided. Estimates are also compared to values computed by molecular detection efficiency simulation. The use of Lorentzian intensity distributions complements conditions where a Gaussian intensity distribution applies, expanding the applicability range of analytical correlation functions.

  • 11.
    Blom, Hans
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Johansson, Mathias
    Gösch, Michael
    Sigmundsson, Toni
    Holm, Johan
    Hård, Sverker
    Rigler, Rudolf
    Parallel Flow Measurements in Microstructures by Use of a Multifocal 4 x 1 Diffractive Optical Fan-Out Element2002Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, nr 31, s. 6614-6620Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have developed a multifocal optical fluorescence correlation spectroscopy system for parallel flow analyses. Multifocal excitation was made possible through a 4 x 1 diffractive optical fan-out element, which produces uniform intensity in all four foci. Autocorrelation flow analyses inside a 20 μm x 20 μm square microchannel, with the 4 x 1 fan-out foci perpendicular to the flow direction, made it possible to monitor different flows in all four foci simultaneously. We were able to perform cross-correlation flow analyses by turning the microstructure, thereby having all four foci parallel to the direction of flow. Transport effects of the diffusion as a function of flow and distance could then also be studied.

  • 12.
    Blom, Hans
    et al.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Johansson, Mathias
    Hedman, Anna-Sara
    Lundberg, Liselotte
    Hanning, Anders
    Hård, Sverker
    Rigler, Rudolf
    Parallel Fluorescence Detection of Single Biomolecules in Microarrays by a Diffractive-Optical-Designed 2 x 2 Fan-Out Element2002Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 41, nr 16, s. 3336-3342Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have developed a multifocal diffractive-optical fluorescence correlation spectroscopy system for parallel excitation and detection of single tetramethylrhodamine biomolecules in microarrays. Multifocal excitation was made possible through the use of a 2 × 2 fan-out diffractive-optical element with uniform intensity in all foci. Characterization of the 2 × 2 fan-out diffractive-optical element shows formation of almost perfect Gaussian foci of submicrometer lateral diameter, as analyzed by thermal motion of tetramethylrhodamine dye molecules in solution. Results of parallel excitation and detection in a high-density microarray of circular wells show single-biomolecule sensitivity in all four foci simultaneously.

  • 13. Boyko, Andrey A.
    et al.
    Kostyukova, Nadezhda Y.
    Badikov, Valeriy
    Badikov, Dmitrii
    Panyutin, Vladimir
    Shevyrdyaeva, Galina
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Marchev, Georgi M.
    Kolker, Dmitry B.
    Petrov, Valentin
    Intracavity difference-frequency mixing of optical parametric oscillator signal and idler pulses in BaGa4Se72017Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, nr 10, s. 2783-2786Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An overall quantum conversion efficiency of 7.8% is achieved by intracavity mixing the signal and idler of a 1.064 mu m pumped Rb: PPKTP optical parametric oscillator in BaGa4Se7. In this way, a pulse energy of similar to 0.71 mJ is generated at similar to 7 mu m for a repetition rate of 100 Hz. Tuning of the mid-IR radiation is demonstrated by heating of the Rb: PPKTP crystal.

  • 14.
    Burvall, Anna
    et al.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Kolacz, K.
    Jaroszewicz, Z.
    Friberg, Ari T.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Simple lens axicon2004Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, nr 25, s. 4838-4844Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the design of a cemented doublet-lens axicon made from spherical surfaces only. Compared with diffractive axicons, refractive cone axicons, and earlier lens axicons with aspheric surfaces, this element is inexpensive and easy to manufacture even with large apertures. The lens axicon is based on the deliberate use of the spherical aberration of the surfaces. The design principles of the element and its characterization, numerically and experimentally, are presented in detail. Although performance was traded for simplicity and robustness, the results show that the lens axicon has the main axicon properties: a narrow, extended line focus of relatively constant width.

  • 15.
    Burvall, Anna
    et al.
    National University of Ireland, Galway.
    Kolacz, Katarzyna
    Institute of Applied Optics, Warsaw.
    Goncharov, Alexander
    National University of Ireland, Galway.
    Jaroszewicz, Zbigniew
    Institute of Applied Optics, Warsaw.
    Dainty, Christopher
    National University of Ireland, Galway.
    Lens axicons in oblique illumination2007Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 3, s. 312-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lens axicons, i.e., lenses or lens systems designed to work like axicons, can be a simple and inexpensive way of generating the characteristic axicon focal line. In the design of most lens axicons, only on-axis properties have been considered. We present the design of a lens axicon with improved off-axis characteristics. It is constructed from a singlet lens but with a double-pass feature that allows for a line of uniform width and a stop positioned to minimize aberrations. We perform off-axis analysis and experiments for this system and for another lens axicon, one designed for its on-axis characteristics. We conclude that the off-axis performance of the double-pass axicon is better than both that of an ordinary cone axicon and that of the other lens axicon.

  • 16. Canning, John
    et al.
    Åslund, Mattias
    Ankiewicz, Adrian
    Dainese, Matteo
    KTH, Tidigare Institutioner                               , Elektronik.
    Fernando, Harendra
    KTH, Tidigare Institutioner                               , Elektronik.
    Sahu, Jayanta Kumar
    KTH, Tidigare Institutioner                               , Elektronik.
    Wosinski, Lech
    KTH, Tidigare Institutioner                               , Elektronik.
    Birefringence control in plasma-enhanced chemical vapor deposition planar waveguides by ultraviolet irradiation2000Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, nr 24, s. 4296-4299Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Complete birefringence compensation is demonstrated in plasma-enhanced chemical vapor deposition waveguides by 193-nm postexposure. A single relaxation process dominates the decay in stress anisotropy, indicating that compressive stress from the substrate leads to an elastic stress anisotropy at the core.

  • 17.
    Carlsson, Torgny E.
    et al.
    KTH, Tidigare Institutioner                               , Industriell produktion.
    Wei, A.
    Phase evaluation of speckle patterns during continuous deformation by use of phase-shifting speckle interferometry2000Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, nr 16, s. 2628-2637Artikkel i tidsskrift (Fagfellevurdert)
  • 18.
    Chang, Jin
    et al.
    Delft Univ Technol, ImPhys Dept, Opt Res Grp, Fac Appl Sci, Lorentzweg 1, NL-2628 CJ Delft, Netherlands..
    Zadeh, Iman Esmaeil
    Delft Univ Technol, ImPhys Dept, Opt Res Grp, Fac Appl Sci, Lorentzweg 1, NL-2628 CJ Delft, Netherlands..
    Los, Johannes W. N.
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Zichi, Julien
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Fognini, Andreas
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Gevers, Monique
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Dorenbos, Sander
    Single Quantum BV, NL-2628 CH Delft, Netherlands..
    Pereira, Silvania F.
    Delft Univ Technol, ImPhys Dept, Opt Res Grp, Fac Appl Sci, Lorentzweg 1, NL-2628 CJ Delft, Netherlands..
    Urbach, Paul
    Delft Univ Technol, ImPhys Dept, Opt Res Grp, Fac Appl Sci, Lorentzweg 1, NL-2628 CJ Delft, Netherlands..
    Zwiller, Val
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Multimode-fiber-coupled superconducting nanowire single-photon detectors with high detection efficiency and time resolution2019Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 58, nr 36, s. 9803-9807Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the past decade, superconducting nanowire single-photon detectors (SNSPDs) have gradually become an indispensable part of any demanding quantum optics experiment. Until now, most SNSPDs have been coupled to single-mode fibers. SNSPDs coupled to multimode fibers have shown promising efficiencies but have yet to achieve high time resolution. For a number of applications ranging from quantum nano-photonics to bio-optics, high efficiency and high time resolution are desired at the same time. In this paper, we demonstrate the role of polarization on the efficiency of multimode-fiber-coupled detectors and fabricated high-performance 20 mu m, 25 mu m, and 50 mu m diameter detectors targeted for visible, near-infrared, and telecom wavelengths. A custom-built setup was used to simulate realistic experiments with randomized modes in the fiber. We achieved over 80% system efficiency and <20 ps timing jitter for 20 mu m SNSPDs. Also, we realized 70% system efficiency and <20 ps timing jitter for 50 mu m SNSPDs. The high-efficiency multimode-fiber-coupled SNSPDs with unparalleled time resolution will benefit various quantum optics experiments and applications in the future.

  • 19.
    Chen, Hongzhi
    et al.
    Zhejiang Univ, Ctr Opt & Electromagnet Res, State Key Lab Modern Opt Instrumentat, Hangzhou 310058, Zhejiang, Peoples R China..
    Yan, Guofeng
    Zhejiang Univ, Ctr Opt & Electromagnet Res, State Key Lab Modern Opt Instrumentat, Hangzhou 310058, Zhejiang, Peoples R China..
    Forsberg, Erik
    Zhejiang Univ, Ctr Opt & Electromagnet Res, State Key Lab Modern Opt Instrumentat, Hangzhou 310058, Zhejiang, Peoples R China..
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. Zhejiang Univ, Ctr Opt & Electromagnet Res, State Key Lab Modern Opt Instrumentat, Hangzhou 310058, Zhejiang, Peoples R China..
    Terahertz polarization splitter based on a dual-elliptical-core polymer fiber2016Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, nr 23, s. 6236-6242Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A terahertz polarization splitter based on a dual-elliptical-core polymer fiber is proposed and theoretically optimized. Dual-elliptical cores with subwavelength-scale diameters are independently suspended within a fiber, which not only support two orthogonal polarization modes, being single-mode guided with low absorption losses, but also allow them to switch from one core to the other, with different coupling lengths. As a consequence, the two polarizations can be easily separated by choosing a suitable transmission length at a desired operation frequency. The transmission modes, coupling lengths for x- and y-polarizations, as well as the performance of the proposed polarization splitter at a center-frequency of 0.6 THz are investigated and numerically analyzed. A 1.43 cm long splitter with an ultralow loss of 0.4 dB, a high extinction ratio better than -10 dB and a bandwidth of 0.02 THz is achieved.

  • 20.
    Cronhjort, Andreas
    et al.
    Scania CV AB.
    Wåhlin, Fredrik
    Scania CV AB.
    Segmentation Algorithm for Diesel Spray Image Analysis2004Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, nr 32, s. 5971-5980Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An algorithm for segmentation of diesel spray images has been developed. Its most important feature is robustness against experimental setups that fail to guarantee images whose histograms show two distinct peaks. According to the approach presented, only the peak from the background is used, and it is assumed that the background peak is narrow enough not to include too much of the spray. The algorithm has proved successful for evaluation of images from a pressurized vessel as well as from an engine with optical access, with no need for adjusting the tuning parameters. By adjusting them, one may tune the noise sensitivity.

  • 21.
    Daemi, Bita
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Ekberg, Peter
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Mattsson, Lars
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Advanced image analysis verifies geometry performance of micro-milling systems2017Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, nr 10, s. 2912-2921Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accurate dimensional measurement of micro-milled items is a challenge and machine specifications do not include operational parameters in the workshop. Therefore, a verification test that shows the machine's overall geometrical performance over its working area would help machine users in the assessment and adjustment of their equipment. In this study, we present an optical technique capable of finding micro-milled features at submicron uncertainty over working areas > 10 cm(2). The technique relies on an ultra-precision measurement microscope combined with advanced image analysis to get the center of gravity of milled cross-shaped features at subpixel levels. Special algorithms had to be developed to handle the disturbing influence of burr and milling marks. The results show repeatability, reproducibility, and axis straightness for three micro-milling facilities and also discovered an unknown 2 mu m amplitude undulation in one of them.

  • 22. Dai, D. X.
    et al.
    He, Sailing
    KTH, Tidigare Institutioner                               , Teoretisk elektroteknik.
    Analysis of multimode effects in the free-propagation region of a silicon-on-insulator-based arrayed-waveguide grating demultiplexer2003Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, nr 24, s. 4860-4866Artikkel i tidsskrift (Fagfellevurdert)
  • 23. Dai, D. X.
    et al.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Design of an ultrashort Si-nanowaveguide-based multimode interference coupler of arbitrary shape2008Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, nr 1, s. 38-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A design procedure for an arbitrarily tapered multimode interference (MMI) coupler based on Si nanowaveguides is presented. First a series of the effective indices of the zeroth and first eigenmodes in multimode waveguides are obtained as the core width increases by using a full-vectorial finite-difference method. Two polynomial functions are used to fit the two relations between the effective indices and the core width. The phase difference Delta phi between the zeroth and first eigenmodes can then be easily calculated when the light goes through any given arbitrarily tapered MMI section. By making the phase difference Delta phi equal to a certain value Delta phi(0) required for an N-fold self-imaging, the length of a MMI coupler is determined. With the present design procedure, an ultrashort 2 x 2 parabolic MMI coupler is designed as an example. The size of the designed ultrashort MMI section is only similar to 1.4 mu m X 4.7 mu m.

  • 24.
    Dai, Daoxin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    He, Jian-Jun
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Compact silicon-on-insulator-based multimode interference coupler with bilevel taper structures2005Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, nr 24, s. 5036-5041Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel compact silicon-on-insulator- (SOI-)based multimode interference (MMI) coupler with bilevel taper structures was designed. The MMI section and the S-bend sections of the input-output waveguides are deeply etched. The input-output waveguides connecting to single-mode fibers or other photonic light circuits are etched shallowly to yield single-mode operation. A bilevel taper is introduced in the transition region between the shallowly and deeply etched regions. It is predicted theoretically that this design will not only improve the quality of the self-imaging in the MMI section but will also make the structure compact. Both the excess loss and the nonuniformity of the MMI coupler are reduced. By use of a three-dimensional beam propagation method, the performance of a 1 × 4 MMI coupler based on a SOI is simulated as a numerical example of the novel design. The simulated nonuniformity and the excess loss are approximately 0.0285 and 0.2 dB, respectively.

  • 25.
    Dai, Daoxin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, Tidigare Institutioner                               , Teoretisk elektroteknik.
    Analysis of the birefringence of a silicon-on-insulator rib waveguide2004Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, nr 5, s. 1156-1161Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A detailed analysis of the polarization characteristics (birefringence) of a silicon-on-insulator (SOI) rib waveguide is given. The fundamental TE- and TM-polarized modes of the SOI rib waveguide are calculated by a semivectorial finite-difference method. The rib width and the slab height of the SOI rib waveguide are normalized with respect to the total height of the silicon layer. A general relation between the two normalized parameters for a nonbirefringent SOI rib waveguide is obtained. According to this relation a nonbirefringent SOI rib waveguide can easily be designed. The fabrication tolerance for a nonbirefringent SOI rib waveguide is also analyzed, revealing that the tolerance can be increased by use of a larger total height of the silicon layer.

  • 26. Dai, Daoxin
    et al.
    Shi, Yaocheng
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Characteristic analysis of nanosilicon rectangular waveguides for planar light-wave circuits of high integration2006Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 45, nr 20, s. 4941-4946Artikkel i tidsskrift (Fagfellevurdert)
  • 27. Dai, Daoxin
    et al.
    Shi, Yaocheng
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Comparative study of the integration density for passive linear planar light-wave circuits based on three different kinds of nanophotonic waveguide2007Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 7, s. 1126-1131Artikkel i tidsskrift (Fagfellevurdert)
  • 28.
    Degerman Engfeldt, Johnny
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Georen, Peter
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, N Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Methodology for measuring current distribution effects in electrochromic smart windows2011Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, nr 29, s. 5639-5646Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrochromic (EC) devices for use as smart windows have a large energy-saving potential when used in the construction and transport industries. When upscaling EC devices to window size, a well-known challenge is to design the EC device with a rapid and uniform switching between colored (charged) and bleached (discharged) states. A well-defined current distribution model, validated with experimental data, is a suitable tool for optimizing the electrical system design for rapid and uniform switching. This paper introduces a methodology, based on camera vision, for experimentally validating EC current distribution models. The key is the methodology's capability to both measure and simulate current distribution effects as transmittance distribution. This paper also includes simple models for coloring (charging) and bleaching (discharging), taking into account secondary current distribution with charge transfer resistance and ohmic effects. Some window-size model predictions are included to show the potential for using a validated EC current distribution model as a design tool.

  • 29.
    Dong, Lin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Sugunan, Abhilash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Hu, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Zhou, Sicheng
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Optik.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Photoluminescence from quasi-type-II spherical CdSe-CdS core-shell quantum dots2013Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 52, nr 1, s. 105-109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spherical CdSe-CdS core-shell quantum dots (QDs) are found to be flexible in the transition between the type-I regime and the type-II regime with different core/shell dimensions. The quasi-type-II feature of the colloidal dots is confirmed with time-resolved photoluminescence (PL) measurements. Two recombination paths of the excitons with significantly different decay rates are observed and analyzed. The spherical CdSe-CdS core-shell QDs are numerically simulated to investigate the carrier separation. A relatively long radiative lifetime and high degree of spatial carrier separation provide good potential to achieve lasing under continuous-wave excitation. Amplified spontaneous emission at room temperature is detected from the QDs embedded in the polymer matrix. It is shown that a larger shell thickness results in a lower pumping threshold, while a smaller shell thickness leads to higher PL efficiency.

  • 30. Fuhse, C
    et al.
    Krebs, H U
    Vitta, S
    Johansson, Göran A.
    KTH, Tidigare Institutioner, Fysik.
    Interface quality and thermal stability of laser-deposited metal/MgO multilayers2004Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, nr 34, s. 6265-6269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal/MgO multilayers (metal of Fe80Ni80Nb20, and Ti) with bilayer periods in the range 1.2-3.0 nm have been prepared by pulsed laser deposition and characterized by both hard and soft-x-ray reflectometry. The interface roughness is found to be less than or equal to 0.5 nm in all the samples and is nearly independent of the total number of deposited bilayers. The interface roughness, however, depends on the absolute thickness of the individual layers and increases from approximate to0.3 nm for a 3.0-nm period to approximate to0.5 nm for a bilayer period of 1.2 nm. The multilayers are found to be highly stable up to temperatures as high as 550 degreesC. The hard-x-ray reflectivity of the multilayers decreases for T > 300 degreesC, whereas the layered structure is stable up to 550 degreesC. The reflectivity in the water window region of soft x rays, lambda = 3.374 nm, was found to be 0.4% at an angle of incidence of approximate to54degrees for multilayers with 60 bilayers at a period of approximate to2.1 nm. (C) 2004 Optical Society of America.

  • 31. Goenka, Chhavi
    et al.
    Semeter, Joshua
    Noto, John
    Baumgardner, Jeffrey
    Riccobono, Juanita
    Migliozzi, Mike
    Dahlgren, Hanna
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marshall, Robert
    Kapali, Sudha
    Hirsch, Michael
    Hampton, Donald
    Akbari, Hassanali
    Multichannel tunable imager architecture for hyperspectral imaging in relevant spectral domains2016Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 55, nr 12, s. 3149-3157Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we present a technique for dimensionality reduction in hyperspectral imaging during the data collection process. A four-channel hyperspectral imager using liquid crystal Fabry-Perot etalons has been built and used to verify this method for four applications: auroral imaging, plant study, landscape classification, and anomaly detection. This imager is capable of making measurements simultaneously in four wavelength ranges while being tunable within those ranges, and thus can be used to measure narrow contiguous bands in four spectral domains. In this paper, we describe the design, concept of operation, and deployment of this instrument. The results from preliminary testing of this instrument are discussed and are promising and demonstrate this instrument as a good candidate for hyperspectral imaging.

  • 32.
    Goncharov, Alexander
    et al.
    National University of Ireland, Galway.
    Burvall, Anna
    National University of Ireland, Galway.
    Dainty, Christopher
    National university of Ireland, Galway.
    Systematic design of anastigmatic lens axicon2007Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 24, s. 6076-6080Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an analytical method for systematic optical design of a double-pass axicon that shows almost no astigmatism in oblique illumination compared to a conventional linear axicon. The anastigmatic axicon is a singlet lens with nearly concentric spherical surfaces applied in double pass, making it possible to form a long narrow focal line of uniform width. The front and the back surfaces have reflective coatings in the central and annular zones, respectively, to provide the double pass. Our design method finds the radii of curvatures and axial thickness of the lens for a given angle between the exiting rays and the optical axis. It also finds the optimal position of the reflecting zones for minimal vignetting. This method is based on ray tracing of the real rays at the marginal heights of the aperture and therefore is superior to any paraxial method. We illustrate the efficiency of the method by designing a test axicon with optical parameters used for a prototype axicon, which was manufactured and experimentally tested. We compare the optical characteristics of our test axicon with those of the experimental prototype.

  • 33. Han, Zhanghua
    et al.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Two-dimensional model for three-dimensional index-guided multimode plasmonic waveguides and the design of ultrasmall multimode interference splitters2007Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 25, s. 6223-6227Artikkel i tidsskrift (Fagfellevurdert)
  • 34.
    Hansson, Björn A. M.
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Mosesson, Sofia
    KTH, Tidigare Institutioner, Fysik.
    Hertz, Hans M.
    KTH, Tidigare Institutioner, Fysik.
    Improved emission uniformity from a liquid-jet laser-plasma extreme-ultraviolet source2004Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, nr 29, s. 5452-5457Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many modern compact soft-x-ray and extreme-ultraviolet (EUV) imaging systems operate with small fields of view and therefore benefit from the use of small high-brightness sources. Such systems include water-window microscopes and ELTV lithography tools. We show that the photon losses in such systems can be minimized while uniformity of object-plane illumination is maintained by controlled scanning of the source. The improved collection efficiency is demonstrated both theoretically and experimentally for a scanned laser-plasma source compared with static sources. A prospective aerial image microscope and a liquid-xenon-jet laser-plasma source are offered as examples of modem imaging tools that may benefit from such scanning of the source.

  • 35. Hansson, G.
    et al.
    Karlsson, H.
    Laurell, Fredrik
    KTH, Tidigare Institutioner, Fysik.
    Unstable resonator optical parametric oscillator based on quasi-phase-matched RbTiOAsO42001Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 40, nr 30, s. 5446-5451Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate improved signal and idler-beam quality of a 3-mm-aperture quasi-phase-matched RbTiOAsO4 optical parametric oscillator through use of a confocal unstable resonator as compared with a plane-parallel resonator. Both oscillators were singly resonant, and the periodically poled RbTiOAsO4 crystal generated a signal at 1.56 mum and an idler at 3.33 mum when pumped at 1.064 mum. We compared the beam quality produced by the 1.2-magnification confocal unstable resonator with the beam quality produced by the plane-parallel resonator by measuring the signal and the idler beam M-2 value. We also investigated the effect of pump-beam intensity distribution by comparing the result of a Gaussian and a top-hat intensity profile pump beam. We generated a signal beam of M-2 approximate to 7 and an idler beam of M-2 approximate to 2.5 through use of an unstable resonator and a Gaussian intensity profile pump beam. This corresponds to an increase of a factor of approximately 2 in beam quality for the signal and a factor of 3 for the idler, compared with the beam quality of the plane-parallel resonator optical parametric oscillator.

  • 36. Hansson, G.
    et al.
    Karlsson, H.
    Wang, S. H.
    Laurell, Fredrik
    KTH, Tidigare Institutioner, Fysik.
    Transmission measurements in KTP and isomorphic compounds2000Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, nr 27, s. 5058-5069Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The optical biaxial nature of crystals in the potassium titanyl phosphate (KTP) family result in anisotropic transmission that depends on the polarization direction of the transmitted radiation with respect to the fundamental crystal axes. Knowledge of the polarization-dependent crystal transmission is important for all wavelength-conversion applications and in particular is the only limitation on possible combinations of wavelengths when one uses the quasi-phase-matching techniques recently developed for the KTP family materials. In this study, polarized transmission spectra of KTiOPO4 (KTP), RbTiOPO4, RbTiOAsO4 (RTA), and KTiOAsO4 were measured over the 0.3-6-mu m wavelength range with a spectrophotometer and a Fourier-transform infrared spectrometer. Seven crystal samples were studied, including four samples of KTP crystals of different origins. Variations in spectral transmission on the short- and long-wavelength edges, as well as visible-wavelength transmission and OH- absorption properties, are presented and discussed. The transmission of one sample of RTP and of RTA was also measured before and after periodic electric field poling.

  • 37.
    He, Sailing
    et al.
    KTH, Tidigare Institutioner                               , Teoretisk elektroteknik.
    Ao, X. Y.
    Romanov, V.
    General properties of N x M self-images in a strongly confined rectangular waveguide2003Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, nr 24, s. 4855-4859Artikkel i tidsskrift (Fagfellevurdert)
  • 38. Huang, Qiangsheng
    et al.
    Cheng, Jianxin
    Liu, Liu
    Tang, Yongbo
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. Zhejiang University, China.
    Ultracompact tapered coupler for the Si/III-V heterogeneous integration2015Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, nr 14, s. 4327-4332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An ultracompact tapered coupler, which is suitable for mode transformation between a 220 nm high silicon wire waveguide and a Si/III-V hybrid waveguide, is proposed for Si/III-V heterogeneous integration. The tapered coupler is composed of three sections. Since the tapered coupler avoids exciting the unwanted high-order modes in the III-V waveguide, the length of the tapered coupler can be dramatically shortened. In the proposed structure, the total length of the trisectional tapered coupler can be as short as 8 mu m with a fundamental mode-coupling efficiency of over 95% in a bandwidth of over 100 nm. The alignment tolerance of the proposed structure is also analyzed.

  • 39.
    Iyer, Srinivasan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Effective tunability and realistic estimates of group index in plasmonic metamaterials exhibiting electromagnetically induced transparency2011Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, nr 21, s. 3958-3961Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the phenomenon of the electromagnetically induced transparency in planar and stacked plasmonic metamaterials (MMs) using the finite integration time domain and finite element methods. For such structures, the dependence of the tunability of the inherent structural resonances on geometry design is clarified. We also analyze the performance of recently demonstrated MM designs in terms of the achievable group refractive index and losses, which are of great interest for slowing light applications.

  • 40.
    Jamid, H. A.
    et al.
    Department of Electrical Engineering, King Fahd Univ. of Petrol./Minerals, Saudi Arabia.
    Akram, Nadeem
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Analysis of antiresonant reflecting optical waveguide gratings by use of the Method of Lines2003Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, nr 18, s. 3488-3494Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modal spectral response of an antiresonant reflecting optical waveguide (ARROW) with periodic corrugations or grating is calculated for both shallow and deep gratings with the Method of Lines. The effect of the ARROW layer thickness and the grating depth on the spectral response is studied. It is found that when the ARROW-layer thickness is close to resonance, the ripples in the reflection spectra become smooth and the peak reflectivity drops. This is attributed to the large increase in the leakage loss of the ARROW waveguide near resonance. The ARROW grating is characterized by modal reflectivity spectra, which exhibit a strong polarization discrimination property, in favor of the TE polarization.

  • 41. Johansson, M.
    et al.
    Lofving, B.
    Hard, S.
    Thylén, Lars
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Mokhtari, M.
    Westergren, Urban
    KTH, Tidigare Institutioner                               , Elektronik.
    Pala, C.
    Study of an ultrafast analog-to-digital conversion scheme based on diffractive optics2000Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, nr 17, s. 2881-2887Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A potentially ultrafast optical analog-to-digital (A/D) converter scheme is proposed and was partly studied experimentally. In the A/D converter scheme the input signal controls the wavelength of a diode laser, whose output beam is incident on a grating. The beam from the grating hits a diffractive optical element in an array. The wavelength determines which element is illuminated. Each element fans out a unique spot-pattern bit code to be read out in parallel by individual detectors. In the experiment all patterns but one from 64 array elements were read out correctly.

  • 42.
    Junique, Stephan
    et al.
    Acreo AB, Kista.
    Wang, Qin
    Acreo AB, Kista.
    Almqvist, S.
    Acreo AB, Kista.
    Guo, J. H.
    Acreo AB, Kista.
    Martijn, Henk
    Acreo AB, Kista.
    Noharet, Bertrand
    Acreo AB, Kista.
    Andersson, Jan Y.
    Acreo AB, Kista.
    GaAs-based multiple-quantum-well spatial light modulators fabricated by a wafer-scale process2005Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, nr 9, s. 1635-1641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The design, fabrication, and characterization of large, two-dimensional multiple-quantum-well modulator arrays are presented. Such arrays present a speed advantage compared with competing technologies such as liquid crystals and micromirrors, which are intrinsically limited to the kilohertz range. We discuss the design compromises to reach high-contrast, low-voltage swing optical structures compatible with complementary metal-oxide semiconductor-based integrated circuits and present experimental results. Contrast ratio of 5:1 (limited by the fill factor), variations in uniformity below 1 nm, and frame rates in excess of 10 kHz are demonstrated. Technology maturity for volume production is also discussed.

  • 43. Karlsson, G.
    et al.
    Myren, N.
    Margulis, W.
    Taccheo, S.
    Laurell, Fredrik
    KTH, Tidigare Institutioner, Fysik.
    Widely tunable fiber-coupled single-frequency Er-Yb: Glass laser2003Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, nr 21, s. 4327-4330Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fiber-coupled tunable Er-Yb:glass minilaser is presented with output power of 40 mW. The laser can be stepwise tuned in single-frequency operation from 1530 to 1560 nm by compressing a fiber Bragg grating that provides selective feedback. Constant output power (fluctuation < 0.8 dB) over the full tuning range is demonstrated. The relative intensity noise spectrum was measured to be <150 dB/Hz for frequencies >2 MHz.

  • 44. Karlsson, G.
    et al.
    Pasiskevicius, Valdas
    KTH, Tidigare Institutioner, Fysik.
    Laurell, Fredrik
    KTH, Tidigare Institutioner, Fysik.
    Tellefsen, J. A.
    Denker, B.
    Galagan, B. I.
    Osiko, V. V.
    Sverchkov, S.
    Diode-pumped Er-Yb: glass laser passively Q switched by use of Co2+: MgAl2O4 as a saturable absorber2000Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, nr 33, s. 6188-6192Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on passively Q-switched operation of a diode-pumped Er-Yb:glass laser with a Co2+:MgAl2O4 plate as a saturable absorber. Optical pulses with peak power exceeding 2 kW and a pulse length of 2.3 ns have been generated. Single-longitudinal-mode Q-switched operation at 1.53 mum has been obtained by use of the Co2+:MgAl2O4 plate as an intracavity etalon. A discussion of the optimal Er3+ concentration as well as optimization of the cavity design is included.

  • 45.
    Kuldkepp, Matias
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Rachlew, Elisabeth
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Hawkes, N. C.
    Schunke, B.
    Accurate polarization measurements with a dual photoelastic modulator2005Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, nr 28, s. 5899-5904Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurements of the polarization effects in multimirror experiments by using a dual photoelastic modulator are described. The effect of single and multiple mirrors in polarization measurements in two and three dimensions is discussed, and experimental results show how symmetrical placement of mirrors in three-dimensional geometry can eliminate changes in the polarization. Calibration procedures for a dual photoelastic modulator and potential error sources such as misalignment of analyzer, signal dc offset, and neglect of aperture size are presented. Mirror-surface evolution and how it can disturb the polarization measurement are also addressed.

  • 46.
    Li, Jingwei
    et al.
    Zhejiang Univ, Chinese Natl Engn Res Ctr Opt Instruments, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Jiang, Wentao
    Zhejiang Univ, Chinese Natl Engn Res Ctr Opt Instruments, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Yao, Xinli
    Zhejiang Univ, Chinese Natl Engn Res Ctr Opt Instruments, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Cai, Fuhong
    Hainan Univ, Mech & Elect Engn Coll, Dept Elect Engn, Haikou 570228, Hainan, Peoples R China..
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. Zhejiang Univ, Chinese Natl Engn Res Ctr Opt Instruments, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China.
    Fast quantitative fluorescence authentication of milk powder and vanillin by a line-scan hyperspectral system2018Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 57, nr 22, s. 6276-6282Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a fast hyperspectral line-scan fluorescence imaging system to verify the feasibility of quantitative fluorescence authentication of powders. Vanillin, which is restricted for use in milk powder, especially in milk powder for infants, is mixed with milk powder in different mass concentrations (5%, 10%, 30%, 50%, 70%, and 90%). Mixed powders are located on a motorized linear stage. A 405 nm line laser is utilized to excite the fluorescence of the sample. Based on galvo scanning, we can generate a laser line with high spatial resolution and high-intensity density on the samples. An imaging spectrometer with a complementary metal-oxide semiconductor (CMOS) camera as detector is built. The spectral range of the spectrometer is 365-810 nm, with about 1 nm spectral resolution. One snapshot of the CMOS can acquire the fluorescent spatial and spectral information of a line region in 100 ms. By scanning the motorized linear stage, we obtain the fluorescence hypercube of the sample. A 100 x 1926 x 1216 hypercube, which covers an area of 15 mm x 5 mm, is obtained in 50 s. The imaging speed can be enhanced further by increasing the intensity of the excitation laser and the sensitivity of the area camera. Fully constrained least squares, a linear spectral mixture analysis, is utilized to analyze the hypercube obtained by our homemade imaging spectrometer, thus obtaining the pixel concentration of vanillin in each mixed powder. Linear regression analysis is used for the pixel concentration and mass concentration of vanillin. A linear relationship with coefficient of determination le equal to one is observed, which demonstrates the capability of fluorescence hyperspectral quantitative analysis in powders.

  • 47. Li, Xiaohui
    et al.
    Zhang, Ziyang
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Qin, Shenying
    Wang, Tao
    Liu, Fangfei
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Su, Yikai
    Sensitive label-free and compact biosensor based on concentric silicon-on-insulator microring resonators2009Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 48, nr 25, s. F90-F94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose an ultracompact parallel label-free biosensor based on concentric silicon-on-insulator microring resonators. Our numerical studies show that the proposed biosensor offers higher sensitivity and a larger detection area than conventional single-ring-based sensors. We analyze the detection sensitivity of the DNA hybridization by immobilizing the probe on top of the double concentric ring resonators and in the ring-ring air gap. For a concentric double-ring system with an area of 27: 646 mu m(2), the bulk detection sensitivity is 683 nm RIU-1. The sensitive uniformity of the system related to the optical field distribution is also studied.

  • 48.
    Liu, Liu
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    He, Sailing
    Design of metal-cladded near-field fiber probes with a dispersive body-of-revolution finite-difference time-domain method2005Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 44, nr 17, s. 3429-3437Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     A dispersive body-of-revolution finite-difference time-domain method is developed to simulate metal-cladded near-field scanning optical microscope (NSOM) probes. Two types of NSOM probe (aperture and plasmon NSOM probes) are analyzed and designed with this fast method. The influence of the metal-cladding thickness and the excitation mode on the performance of the NSOM probes is studied. We introduce a new scheme of illumination-mode NSOM by employing the plasmon NSOM probe with the TM01 mode excitation. Such a NSOM probe is designed, and we demonstrate its advantages over the conventional aperture NSOM probe by scanning across a metallic object.

  • 49. Liu, Shih-Chia
    et al.
    Zhao, Deyin
    Liu, Yonghao
    Yang, Hongjun
    Sun, Yuze
    Ma, Zhengqiang
    Reuterskiold-Hedlund, Carl
    Hammar, Mattias
    Zhou, Weidong
    Photonic crystal bandedge membrane lasers on silicon2017Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, nr 31, s. H67-H73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report here the design and experimental demonstration of optically pumped photonic crystal bandedge membrane lasers on silicon-on-insulator (SOI) and on bulk silicon (Si) substrates, based on heterogeneously integrated InGaAsP multi-quantum-well membrane layers transfer printed onto patterned photonic crystal cavities. Singlemode lasing under room-temperature operation was observed at 1542 nm, with excellent side mode suppression ratio greater than 31.5 dB, for the laser built on SOI substrate. For the laser built on bulk Si substrate, single-mode lasing was also achieved at 1452 nm with much lower thermal resistance, as compared to that of the laser built on SOI substrates. Such improved thermal characteristics are favorable for lasers operating potentially at higher temperatures and higher power.

  • 50.
    Margulis, Walter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Yu, Zhangwei
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Malmström, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Rugeland, Patrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Knape, Harald
    Tarasenko, Oleksandr
    High-speed electrical switching in optical fibers [Invited]2011Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, nr 25, s. E65-E75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we give an overview of recent results on switching of light in fibers with internal electrodes. Polarization rotation, nanosecond gating, and wavelength switching in fiber Bragg gratings and in long period gratings are discussed. Applications are exemplified in Q-switching fiber lasers and in RF-signal filtering.

12 1 - 50 of 70
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