Change search
Refine search result
1 - 14 of 14
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Calil Kores, Cristine
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Department of Applied Physics, School of Engineering Sciences, Roslagstullsbacken 21, 10691 Stockholm, Sweden .
    Ismail, Nur
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Dijkstra, Meindert
    Bernhardi, Edward
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Visiting scientist .
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Advanced Technology Institute, Department of Electrical and Electronic Engineering, University of Surrey, Guildford GU2 7XH, UK.
    Temperature dependence of the spectral characteristics of distributed-feedback resonators2018In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 4, p. 4892-4905Article in journal (Refereed)
    Abstract [en]

    We characterize the spectral response of a distributed-feedback resonator when subject to a thermal chirp. An Al2O3 rib waveguide with a corrugated surface Bragg grating inscribed into its SiO2 top cladding is experimentally investigated. We induce a near-to-linear temperature gradient along the resonator, leading to a similar variation of the grating period, and characterize its spectral response in terms of wavelength and linewidth of the resonance peak. Simulations are carried out, showing good agreement with the experimental results and indicating that the wavelength of the resonance peak is a result only of the total accumulated phase shift. For any chirp profile we are able to calculate the reflectivities at the resonance wavelength, and this information largely explains how the linewidth of the resonance changes. This result shows that the increase in linewidth is governed by the increase of the resonator outcoupling losses. 

  • 2.
    Geskus, Dimitri
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Jakutis-Neto, J.
    Spence, D. J.
    Pask, H. M.
    Wetter, N. U.
    Extreme linewidth broadening in a Nd: YLiF4-KGW intracavity Raman laser2014In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Conference paper (Refereed)
  • 3.
    Geskus, Dimitri
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Centro de Lasers e Aplicacoes, IPEN/SP.
    Jakutis-Neto, Jonas
    Instituto de Estudos Avancados, IEAv-DCTA.
    Spence, D. J.
    MQ Photonics, Department of Physics and Astronomy, Macquarie University.
    Pask, H. M.
    MQ Photonics, Department of Physics and Astronomy, Macquarie University.
    Wetter, N. U.
    Centro de Lasers e Aplicacoes, IPEN/SP.
    Extreme Linewidth Broadening in a Nd:YLiF4-KGW Intracavity Raman Laser2015Conference paper (Refereed)
    Abstract [en]

    Linewidth broadening of up to 4 nm of the fundamentaleld has been observed in a intracavity Nd:YLF-KGW Ramanlaser. Nine laser congurations have been analyzedto identify the responsible processes using a mathematicalmodel.

  • 4.
    Geskus, Dimitri
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Yong, Y. S.
    Bernhardi, E. H.
    Agazzi, L.
    García-Blanco, S. M.
    Aravazhi, S.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Concentration dependence of optical gain in Yb3+-doped potassium double tungstate channel waveguides2014In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Conference paper (Refereed)
  • 5.
    Ismail, Nur
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Calil Kores, Cristine
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    The Fabry-Pérot resonator: Spectral line shapes, generic and related Airy distributions, linewidths, finesses, and performance at low or frequency-dependent reflectivity2016In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 15, p. 16366-16389Article in journal (Refereed)
    Abstract [en]

    We systematically characterize the Fabry-Pérot resonator. We derive the generic Airy distribution of a Fabry-Pérot resonator, which equals the internal resonance enhancement factor, and show that all related Airy distributions are obtained by simple scaling factors. We analyze the textbook approaches to the Fabry-Pérot resonator and point out various misconceptions. We verify that the sum of the mode profiles of all longitudinal modes is the fundamental physical function that characterizes the Fabry-Pérot resonator and generates the Airy distribution. Consequently, the resonator losses are quantified by the linewidths of the underlying Lorentzian lines and not by the measured Airy linewidth. Therefore, we introduce the Lorentzian finesse which provides the spectral resolution of the Lorentzian lines, whereas the usually considered Airy finesse only quantifies the performance of the Fabry-Pérot resonator as a scanning spectrometer. We also point out that the concepts of linewidth and finesse of the Airy distribution of a Fabry-Pérot resonator break down at low reflectivity. Furthermore, we show that a Fabry-Pérot resonator has no cut-off resonance wavelength. Finally, we investigate the influence of frequency-dependent mirror reflectivities, allowing for the direct calculation of its deformed mode profiles.

  • 6.
    Ismail, Nur
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Kores, Cristine Calil
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Geskus, Dimitri
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pollnau, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Mode profiles and Airy distributions of Fabry-Perot resonators with frequency-dependent mirror reflectivity2017In: Laser Resonators, Microresonators, and Beam Control XIX / [ed] Kudryashov, AV Paxton, AH Ilchenko, VS, SPIE - International Society for Optical Engineering, 2017, Vol. 10090, article id UNSP 1009011-1Conference paper (Refereed)
    Abstract [en]

    We thoroughly investigate the Fabry-Perot resonator, avoid approximations, and derive its generic Airy distribution, equaling the internal resonance enhancement, and all related Airy distributions, such as the commonly known transmission. We verify that the sum of the mode profiles of all longitudinal modes is the fundamental physical function characterizing the Fabry-Perot resonator and generating the Airy distributions. We investigate the influence of frequency-dependent mirror reflectivities on the mode profiles and the resulting Airy distributions. The mode profiles then deviate from simple Lorentzian lines and exhibit peaks that are not located at resonant frequencies. Our simple, yet accurate analysis greatly facilitates the characterization of Fabry-Perot resonators with strongly frequency-dependent mirror reflectivities.

  • 7. Kores, C. C.
    et al.
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pask, H. M.
    Wetter, N. U.
    Diode side pumped, quasi-CW Nd:YVO4 self-Raman laser operating at 1176 nm2015In: Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2015, p. 934718-1-934718-6Conference paper (Refereed)
    Abstract [en]

    In this work we demonstrate for the first time, to the best of our knowledge, quasi-continuous wave (qcw) laser operation of a diode-side-pumped Nd:YVO<inf>4</inf> self-Raman laser operating at 1176 nm. The double beam mode controlling (DBMC) technique used in this work allows fundamental mode laser oscillation, resulting in a beam quality M2 of 2.42 and 2.18 in the horizontal and vertical directions, respectively. More than 3.5 W of peak output power at 1176 nm was achieved with TEM<inf>00</inf> laser mode, corresponding to an optical conversion efficiency of 5.4%. With multimode operation, more than 8W of peak output power was achieved, corresponding to 11.7% optical conversion efficiency.

  • 8. Kores, C. C.
    et al.
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pask, H. M.
    Wetter, N. U.
    Diode-side-pumped, continuous-wave Nd:YVO4 self-Raman laser at 1176nm based on DBMC technology2014In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Conference paper (Refereed)
  • 9.
    Kores, Cristine C.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Geskus, Dimitri
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Ismail, Nur
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dijkstra, Meindert
    Bernhardi, Edward H.
    KTH, School of Information and Communication Technology (ICT).
    Pollnau, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    The linewidth of distributed feedback resonators: the combined effect of thermally induced chirp and gain narrowing2017In: Laser Resonators, Microresonators, and Beam Control XIX / [ed] Kudryashov, AV Paxton, AH Ilchenko, VS, SPIE - International Society for Optical Engineering, 2017, article id UNSP 1009014-1Conference paper (Refereed)
    Abstract [en]

    Distributed-feedback (DFB) laser resonators are widely recognized for their advantage of generating laser emission with extremely narrow linewidth. Our investigation concerns ytterbium-doped amorphous Al2O3 channel waveguides with a corrugated homogeneous Bragg grating inscribed into its SiO2 top cladding, in which lambda/4 phase-shift provides a resonance and allows for laser emission with a linewidth as narrow as a few kHz. Pump absorption imposes a thermal chirp of the grating period, which has implications for the spectral characteristics of the resonator. Thermal effects on the spectral response of a DFB passive resonator were investigated via simulations using Coupled Mode Theory by considering (i) a constant deviation of the grating period or (ii) a chirp with a linear profile. We report an increase of the resonance linewidth up to 15%. This result is due to two factors, namely changes of the grating reflectivity at the resonance frequency up to 2.4% and of the shift of resonance frequency up to 61 pm due to an accumulated phase shift imposed on the grating by the chirp profile. The linewidth decrease due to gain is on the order of 106, which is a much larger value. Nevertheless, according to the Schawlow-Townes equation the linewidth increase of the passive resonator due to a thermal chirp quadratically increases the laser linewidth.

  • 10.
    Kores, Cristine Calil
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Ismail, Nur
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Geskus, Dimitri
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dijkstra, M.
    Bernhardi, Edward H.
    Pollnau, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Frequency and linewidth dependence of distributed-feedback resonators on thermal chirp2017In: 2017 19th International Conference on Transparent Optical Networks (ICTON), IEEE Computer Society, 2017, article id 8025100Conference paper (Refereed)
    Abstract [en]

    We present an analysis of the spectral characteristics of distributed-feedback (DFB) laser resonators with thermally chirped distributed mirrors. Such DFB resonators have the interesting capability of producing a linewidth as narrow as a few kHz. The investigated devices are ytterbium-doped amorphous Al2O3 channel waveguides with a periodic Bragg grating inscribed into its SiO2 top cladding. The resonance in the spectral response of the resonator results from a distributed λ/4 phase-shift produced by increasing the waveguide width. Its frequency is determined by the period of the Bragg grating, whereas its linewidth is determined by the intrinsic losses and the outcoupling losses of the resonator. When such a device is optically pumped to achieve gain and eventually lasing, the grating period becomes thermally chirped, thereby influencing the spectral characteristics of the resonator. We investigate experimentally and via simulations the frequency and linewidth of the resonance in the presence of a thermally induced linear chirp on the grating profile. Experiments and simulations show good quantitative agreement.

  • 11.
    Kores, Cristine Calil
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Ismail, Nur
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Dijkstra, M.
    Bernhardi, Edward H.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Spectral broadening in distributed-feedback resonators due to thermal chirp2018In: Optics InfoBase Conference Papers, Optical Society of America, 2018Conference paper (Refereed)
    Abstract [en]

    We investigate the spectral response of an unpumped distributed-feedback waveguide resonator, subject to thermal chirp. Experimental and simulated results indicate that such chirp causes an increase in outcoupling losses and, therefore, in the resonance linewidth.

  • 12. Kores, Cristine Calil
    et al.
    Jakutis-Neto, Jonas
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Pask, Helen M.
    Wetter, Niklaus U.
    Diode-side-pumped continuous wave Nd3+: YVO4 self-Raman laser at 1176 nm2015In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 40, no 15, p. 3524-3527Article in journal (Refereed)
    Abstract [en]

    Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd+3: YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd+3: YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.

  • 13. Reijn, S. -M
    et al.
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Wetter, N. U.
    Investigation of the geometrical depth of focus of focal spots obtained by scattering lenses operating in the transversal and lateral direction2014In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Conference paper (Refereed)
  • 14.
    Reijn, Saara-Maarit
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Inst Pesquisas Energet & Nucl, Ctr Lasers & Aplicacoes, BR-05508000 Sao Paulo, Brazil.
    Pinheiro, Felipe A.
    Univ Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio De Janeiro, Brazil.;Univ Southampton, Optoelect Res Ctr, Southampton SO17 1BJ, Hants, England.;Univ Southampton, Ctr Photon Metamat, Southampton SO17 1BJ, Hants, England..
    Geskus, Dimitri
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Inst Pesquisas Energet & Nucl, Ctr Lasers & Aplicacoes, BR-05508000 Sao Paulo, Brazil.
    Wetter, Niklaus U.
    Inst Pesquisas Energet & Nucl, Ctr Lasers & Aplicacoes, BR-05508000 Sao Paulo, Brazil..
    Enabling focusing around the corner in multiple scattering media2015In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 25, p. 7740-7746Article in journal (Refereed)
    Abstract [en]

    We report an alternative experimental setup to laterally focus light at an angle of 90 deg relative to turbid, multiple scattering media, using preprocessing wavefront shaping. We compare the measured image quality to one obtained in the usual configuration for focusing light through turbid media, where focusing occurs behind the scattering sample. We demonstrate that the depth of focus in the lateral configuration is of the same order of the usual transversal one because both setups are designed to operate in the deep Fresnel zone. This result shows that this novel, versatile lateral configuration allows for effectively focusing around corners through multiple scattering samples.

1 - 14 of 14
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf