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  • 1. Carlsson, C.
    et al.
    Modh, P.
    Halonen, J.
    Schatz, Richard
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Larsson, A.
    High-frequency analog modulation of oxide confined 670-nm vertical-cavity surface-emitting lasers2004Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 43, nr 12, s. 3138-3141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the bandwidth limitations and the analog modulation characteristics at microwave frequencies (0.1 to 10 GHz)of a low-capacitance oxide-confined 670-nm InGaAIP vertical-cavity surface-emitting laser (VCSEL). A maximum modulation bandwidth of 6.3 GHz, limited by thermal effects, is achieved. From measurements of distortion and noise, a spurious free dynamic range (SFDR) of 100 dB Hz(2/3) is obtained at frequencies up to 2 GHz, rendering such VCSELs useful for transmission of analog signals. At higher frequencies, the SFDR drops due to the thermally limited resonance frequency.

  • 2.
    Carlsson, Torgny E.
    et al.
    KTH, Tidigare Institutioner                               , Industriell produktion.
    Nilsson, B.
    Gustafsson, J.
    System for acquisition of three-dimensional shape and movement using digital Light-in-Flight holography2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 1, s. 67-75Artikkel i tidsskrift (Fagfellevurdert)
  • 3.
    Dong, Hui
    et al.
    Nanyang Techbological University, Singapore.
    Shum, Ping
    Nanyang Techbological University, Singapore.
    Gong, Yandong
    Yan, Min
    Nanyang Techbological University, Singapore.
    Zhou, Junqiang
    Wu, Chongqing
    Measurement of polarization mode dispersion vectors in optical fibers using a virtual Mueller matrix method2007Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 46, nr 3, s. 035007-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A virtual Mueller matrix method is proposed to measure the first- and second-order polarization mode dispersion (PMD) vectors in optical fibers. This method not only can use a large frequency step to attain low-noise PMD vector data, but also does not require knowledge of the input polarization states. Our measurement method has a simpler setup and is more accurate than the traditional Mueller matrix method.

  • 4. Eriksson, F.
    et al.
    Johansson, G. A.
    Hertz, Hans M.
    KTH, Tidigare Institutioner                               , Fysik.
    Birch, J.
    Enhanced soft x-ray reflectivity of Cr/Sc multilayers by ion-assisted sputter deposition2002Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 41, nr 11, s. 2903-2909Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cr/Sc multilayers have been grown on Si substrates using dc magnetron sputtering. The multilayers are intended as condenser mirrors in a soft x-ray microscope operating at the wavelength 3.374 nm. They were designed for normal reflection of the first and second orders, with multilayer periods of 1.692 and 3.381 nm, and layer thickness ratios of 0,471 and 0.237, respectively. At-wavelength soft-x-ray reflectivity measurements were carried out using a reflectometer with a compact soft-x-ray laser-plasma source. The multilayers were irradiated during growth with Ar ions, varying both in energy (9 to 113 eV) and flux, in order to stimulate the adatom mobility and improve the interface flatness. It was found that to obtain a maximum soft x-ray reflectivity with a low flux (Cr=0.76, Sc=2.5) of Ar ions a rather high energy of 53 eV was required, Such energy also caused intermixing of the layers. By the use of a solenoid surrounding the substrate, the arriving ion-to-metal flux ratio could be increased 10 times and the required ion energy could be decreased. A high flux (Cr=7.1, Sc=23.1) of low-energy (9 eV) Ar ions yielded the most favorable growth condition, limiting the intermixing with a subsistent good surface flatness.

  • 5. Granberg, H.
    et al.
    Jensen, J.
    Mattsson, Lars
    KTH, Tidigare Institutioner                               , Industriell produktion.
    Forward scattering of fiber-containing surfaces studied by 3-D reflectance distribution simulations and measurements2003Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 42, nr 8, s. 2384-2390Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent studies have shown that the angular distribution of diffuse reflectance, obtained from bidirectional reflectance distribution function (BRDF) measurements, differs strongly between paper sheets with and without fibers present in the top surface layer. For fiber-containing surfaces, in contrast to pigment-coated paper surfaces, there is a distinct forward scattering at angles much larger than the specular reflection angle. In the search for an explanation of this phenomenon, we have made calculations of reflectance distributions of a simulated paper web, containing randomly distributed hollow fibers. We did this on the assumption that fibers present in paper are considerably larger than the wavelength of visible light, and that the surface microroughness of the fibers can be treated as a diffraction broadening superposed on the ray calculated reflectance distribution. We investigate whether the structural shape and distribution of wood fibers can explain some of the observed forward-scattering phenomenon. We also compare these Monte-Carlo ray tracing calculations qualitatively with experimental BRDF measurements of the diffuse reflectance from a fiber-containing surface. From the calculations we found that the reflection at the inner fiber wall of the hollow fibers constituting the topmost layer plays a major role in forming a forward-scattering reflectance distribution. We also found that the Monte-Carlo-calculated bulk scattering distribution, i.e., the distribution of reflected light after a large number of reflections within the web structure, tended to be elongated perpendicular to the sheet plane of the fiber web, rather than being uniform.

  • 6.
    Hemberg, Oskar
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Otendal, Mikael
    KTH, Tidigare Institutioner, Fysik.
    Hertz, Hans M.
    KTH, Tidigare Institutioner, Fysik.
    A Liquid-Metal-Jet Anode X-Ray Tube2004Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 43, nr 7, s. 1682-1688Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a novel electron-impact x-ray source based on a high-speed liquid-metal-jet anode. Thermal power load calculations indicate that this new anode concept potentially could increase the achievable brightness in compact electron-impact x-ray sources by more than a factor 100 compared to current state-of-the-art rotating-anode or microfocus sources. A first, successful, low-power proof-of-principle experiment is described and the feasibility of scaling to high-brightness and high-power operation is discussed. Some possible applications that would benefit from such an increase in brightness are also briefly

  • 7. Hermann, D. S.
    et al.
    Scalia, G.
    Pitois, C.
    De Marco, F.
    D'Have, K.
    Abbate, G.
    Lindgren, M.
    Hult, Anders
    KTH, Tidigare Institutioner                               , Polymerteknologi.
    Novel passive polymer waveguides integrated with electro-optically active ferroelectric liquid crystals2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 10, s. 2188-2198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report the preparation and characterization of novel isotropic polymer slab waveguides made by photochemical crosslinking, and their integration with a ferroelectric liquid crystal in an integrated electro-optic modulator. The refractive index of the passive copolymer material in the device was controlled by the copolymer composition, and good agreement between measured and calculated effective indices for the guided modes of polymer films was obtained. The active ferroelectric liquid crystal exhibited a refractive index change of Deltan approximate to0.10 upon application of an ac voltage of +/- 30 V, giving an electro-optic modulation of the input TE0-mode with a contrast ratio of 11:1 and only a small polarization conversion into TM output light.

  • 8. Kazmierczak, Andrzej
    et al.
    Dortu, Fabian
    Schrevens, Olivier
    Giannone, Domenico
    Vivien, Laurent
    Marris-Morini, Delphine
    Bouville, David
    Cassan, Eric
    Gylfason, Kristinn B.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik.
    Sohlström, Hans
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik.
    Sanchez, Benito
    Griol, Amadeu
    Hill, Daniel
    Light coupling and distribution for Si3N4/SiO2 integrated multichannel single-mode sensing system2009Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 48, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an efficient and highly alignment-tolerant light coupling and distribution system for a multichannel Si3N4/SiO2 single-mode photonics sensing chip. The design of the input and output couplers and the distribution splitters is discussed. Examples of multichannel data obtained with the system are given.

  • 9. Li, J. S.
    et al.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Electro-optic modulator based on Si2N2O substrate2006Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 45, nr 1Artikkel i tidsskrift (Fagfellevurdert)
  • 10. Lofdahl, M. G.
    et al.
    Eriksson, Henrik
    KTH, Tidigare Institutioner                               , Numerisk analys och datalogi, NADA.
    Algorithm for resolving 2 pi ambiguities in interferometric measurements by use of multiple wavelengths2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 6, s. 984-990Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurement of differences in optical path length in monochromatic light with any interferometric method is insensitive to errors that are whole numbers of waves. If measurements are performed in several wavelengths, this ambiguity can be resolved. We present a general algorithm for finding the correct distance post facto, given multiple measurements in different wavelengths. Applied to piston measurements of a segmented mirror, the capture range of a wavefront sensor can be extended from +/- half a wave to several waves. The extended capture range can be calculated and depends on the selection of wavelengths used for measurements and the expected accuracy of the method used.

  • 11.
    Metaferia, Wondwosen
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Simozrag, Bouzid
    Junesand, Carl
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA. Epiclarus AB, Sweden.
    Sun, Yanting
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Carras, Mathieu
    Blanchard, Romain
    Capasso, Federico
    Lourdudoss, Sebastian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Demonstration of a quick process to achieve buried heterostructure quantum cascade laser leading to high power and wall plug efficiency2014Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 53, nr 8, s. 087104-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Together with the optimal basic design, buried heterostructure quantum cascade laser (BH-QCL) with semi-insulating regrowth offers a unique possibility to achieve an effective thermal dissipation and lateral single mode. We demonstrate here the realization of BH-QCLs with a single-step regrowth of highly resistive (>1 x 10(8) ohm . cm) semi-insulating InP: Fe in <45 min for the first time in a flexible hydride vapor phase epitaxy process for burying ridges etched down to 10 to 15 mu m depth, both with and without mask overhang. The fabricated BH-QCLs emitting at similar to 4.7 and similar to 5.5 mu m were characterized. 2-mm-long 5.5-mu m lasers with a ridge width of 17 to 22 mu m, regrown with mask overhang, exhibited no leakage current. Large width and high doping in the structure did not permit high current density for continuous wave (CW) operation. 5-mm-long 4.7-mu m BH-QCLs of ridge widths varying from 6 to 14 mu m regrown without mu mask overhang, besides being spatially monomode, TM00, exhibited wall plug efficiency (WPE) of similar to 8 to 9% with an output power of 1.5 to 2.5 W at room temperature and under CW operation. Thus, we demonstrate a quick, flexible, and single-step regrowth process with good planarization for realizing buried QCLs leading to monomode, high power, and high WPE.

  • 12. Nilsson, B.
    et al.
    Carlsson, Torgny E.
    KTH, Tidigare Institutioner                               , Industriell produktion.
    Simultaneous measurement of shape and deformation using digital light-in-flight recording by holography2000Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 39, nr 1, s. 244-253Artikkel i tidsskrift (Fagfellevurdert)
  • 13.
    Pang, Xiaodan
    et al.
    Technical University of Denmark, Denmark.
    Yu, Xianbin
    Zhao, Ying
    Deng, Lei
    Zibar, Darko
    Monroy, Idelfonso Tafur
    Experimental characterization of a hybrid fiber-wireless transmission link in the 75 to 110 GHz band2012Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 51, nr 4, artikkel-id 045004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a detailed experimental investigation of a hybrid optical-fiber wireless communication system operating at the 75 to 110 GHz (W-band) for meeting the emerging demands in short-range wireless applications. Measured W-band wireless channel properties such as channel loss, frequency response, phase noise, and capacity are reported. Our proposed system performs a sextuple frequency up-conversion after 20 km of fiber transmission, followed by a W-band wireless link. A 500 Mbit/s amplitude shift keying signal transmission is experimentally demonstrated for performance analysis purposes.

  • 14.
    Shi, Yaocheng
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Shahid, Naeem
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Li, Mingyu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Berrier, Audrey
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Anand, Srinivasan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Experimental demonstration of an ultracompact polarization beamsplitter based on a multimode interference coupler with internal photonic crystals2010Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 49, nr 6, s. 060503-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fabrication and characterization of a compact InP-based polarization beamsplitter (PBS) is presented. A multimode interference (MMI) coupler with an internal air hole photonic crystal (PhC) section is utilized to separate the two polarizations. The PhC structure in the middle of the MMI is polarization dependent, so that one polarization is reflected and the other one is transmitted; both are collected by the respective output ports of the MMI coupler. The obtained experimental results show that the PBS as short as similar to 400 mu m has an extinction ratio as large as 15 dB.

  • 15. Sjoeberg, Henrik
    et al.
    Manneberg, Goran
    Cronhjort, Andreas
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Förbränningsmotorteknik.
    Long-working-distance microscope used for diesel injection spray imaging1996Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An optical system for analysis of diesel spray penetration and atomization has been developed. The basic system is based on a microscope with a long working distance (230 mm) and a modest resolution. The magnification is variable between 1:1 and 50:1 on the camera plane. This enables the study of individual droplets with a diameter of 5 mm. A number of different techniques have been used together with the basic system to study different parts of the spray. They include the darkground technique, double exposure, and ordinary magnification. The size, speed, and direction of propagation of the individual droplets have been calculated using the elongation of the droplet image caused by the duration time of the flash.

  • 16. Streubel, K.
    et al.
    Hammar, Mattias
    KTH, Tidigare Institutioner                               , Elektronik.
    Salomonsson, F.
    Bentell, J.
    Mogg, S.
    Rapp, S.
    Jacquet, J.
    Boucart, J.
    Stark, C.
    Plais, A.
    Gaborit, F.
    Derouin, E.
    Bouche, N.
    Rudra, A.
    Syrbu, A. V.
    Iakovlev, V. P.
    Berseth, C. A.
    Dehaese, O.
    Kapon, E.
    Moussa, H.
    Sagnes, I.
    Novel technologies for 1.55-mu m vertical cavity lasers2000Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 39, nr 2, s. 488-497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on three novel vertical-cavity laser (VCL) structures for 1.55-mu m operation. Two of the structures utilize an n-type GalnAsP/InP Bragg mirror combined with an Al(Ga)As/GaAs mirror using either wafer fusion or metamorphic epitaxial growth. The third employs two wafer-fused AlGaAs/GaAs mirrors, in which lateral current confinement is obtained by localized fusion of the p mirror. Ali three VCLs use strained GalnAsP quantum welts as active material and achieve continuous-wave (cw) operation at room temperature or above. The single fused VCL operates up to 17 and 101 degrees C in continuous-wave and pulsed mode, respectively. The monolithic VCL-structure with a metamorphic GaAs/AlAs n-type mirror uses a reverse-biased tunnel junction for current injection. This laser achieves record high output power (1 mW) at room temperature and operates cw up to 45 degrees C. The double fused VCLs with a 10x10-mu m(2) active area operate cw up to 30 degrees C with threshold current as low as 2.5 mA and series resistance of 30 Omega. The emission spectra exhibit a single lasing mode polarized with 30-dB extinction ratio and a spectral linewidth of 150 MHz.

  • 17. Wang, Q.
    et al.
    He, Sailing
    Yu, F. H.
    Huang, N. R.
    Iterative finite-difference method for calculating the distribution of a liquid-crystal director2001Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 40, nr 11, s. 2552-2557Artikkel i tidsskrift (Fagfellevurdert)
1 - 17 of 17
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