| 1. |
- Calil Kores, Cristine, et al.
(author)
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Temperature dependence of the resonance line of optically pumped distributed-feedback lasers
- 2018
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In: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580484
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Conference paper (peer-reviewed)abstract
- We characterize experimentally and theoretically a distributed-feedback laser resonator subject to a thermal chirp. The total accumulated phase shift determines the resonance wavelength. The reflectivities (outcoupling losses) at the resonance wavelength govern the resonance linewidth.
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| 2. |
- Calil Kores, Cristine, et al.
(author)
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Temperature dependence of the spectral characteristics of distributed-feedback resonators
- 2018
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In: Optics Express. - 1094-4087. ; 26:4, s. 4892-4905
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Ismail, Nur, et al.
(author)
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Mode profiles and Airy distributions of Fabry-Perot resonators with frequency-dependent mirror reflectivity
- 2017
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In: Laser Resonators, Microresonators, and Beam Control XIX. - : SPIE - International Society for Optical Engineering. - 9781510606210 - 9781510606227
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Conference paper (peer-reviewed)abstract
- 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.
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| 4. |
- Ismail, Nur, 1977-, et al.
(author)
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The Fabry-Pérot resonator: Spectral line shapes, generic and related Airy distributions, linewidths, finesses, and performance at low or frequency-dependent reflectivity
- 2016
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In: Optics Express. - : Optical Society of America. - 1094-4087. ; 24:15, s. 16366-16389
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Journal article (peer-reviewed)abstract
- 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.
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| 5. |
- Kores, Cristine Calil, et al.
(author)
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Accumulation of distributed phase shift in distributed-feedback lasers
- 2018
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In: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580484
-
Conference paper (peer-reviewed)abstract
- In distributed-feedback lasers, a distributed phase shift of /2, seemingly placing the resonance at the Bragg wavelength, is not accumulated because of light confinement and asymmetry, leading to a systematic resonance shift to shorter wavelengths.
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| 6. |
- Kores, Cristine Calil, et al.
(author)
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Accumulation of Distributed Phase Shift in Distributed-Feedback Resonators
- 2019
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In: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 11:1
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Journal article (peer-reviewed)abstract
- Distributed-feedback waveguide lasers based on Bragg-grating resonators generate ultranarrow-linewidth emission. Oscillation at the center of the reflection band ensures maximum reflectivity, hence minimum linewidth. The required pi/2 phase shift is often introduced by a distributed change in effective refractive index, e.g., by widening the waveguide. Despite careful design and fabrication, the experimentally observed resonance wavelength deviates from the designed wavelength. Even when thermally induced chirp or fabrication errors are negligible, this deviation is still present. Here, we show theoretically and experimentally that this deviation is of fundamental nature. The decay of light intensity during propagation from the phase-shift center into both sides of the Bragg grating due to reflection by the periodic grating and the refractive index change causes an incomplete accumulation of designed phase shift, thereby systematically shifting the resonance to a shorter wavelength. Considering the overlap integral between the distributed phase shift and light intensity in the design provides the desired performance.
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| 7. |
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| 8. |
- Kores, Cristine Calil, et al.
(author)
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Diode-side-pumped continuous wave Nd3+ : YVO4 self-Raman laser at 1176 nm
- 2015
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 40:15, s. 3524-3527
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
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| 10. |
- Kores, Cristine Calil, et al.
(author)
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Frequency and linewidth dependence of distributed-feedback resonators on thermal chirp
- 2017
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In: 2017 19th International Conference on Transparent Optical Networks (ICTON). - : IEEE Computer Society. - 9781538608586
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Conference paper (peer-reviewed)abstract
- 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.
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