Q Factors

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Susumu Noda - One of the best experts on this subject based on the ideXlab platform.

  • sub 100 nw threshold raman silicon laser designed by a machine learning method that optimizes the product of the cavity Q Factors
    Optics Express, 2021
    Co-Authors: Taro Kawakatsu, Susumu Noda, Takashi Asano, Yasushi Takahashi
    Abstract:

    Raman silicon lasers based on photonic crystal nanocavities with a threshold of several hundred microwatts for continuous-wave lasing have been realized. In particular, the threshold depends on the degree of confinement of the excitation light and the Raman scattering light in the two nanocavity modes. Here, we report lower threshold values for Raman silicon nanocavity lasers achieved by increasing the Quality (Q) Factors of the two cavity modes. By using an optimization method based on machine learning, we first increase the product of the two theoretical Q values by a factor of 17.0 compared to the conventional cavity. The experimental evaluation demonstrates that, on average, the actually achieved product is more than 2.5 times larger than that of the conventional cavity. The input–output characteristic of a Raman laser with a threshold of 90 nW is presented and the lowest threshold obtained in our experiments is 40 nW.

  • analysis of Q Factors of structural imperfections in triangular cross section nanobeam photonic crystal cavities
    Journal of The Optical Society of America B-optical Physics, 2015
    Co-Authors: Yuki Yamaguchi, Seungwoo Jeon, Bongshik Song, Takashi Asano, Yoshinori Tanaka, Susumu Noda
    Abstract:

    We present comprehensive and Quantitative analysis of the effect of structural imperfections on Quality (Q)-Factors in triangular cross-section nanobeam photonic crystal cavities. We investigated statistically the optical losses due to the various imperfections in the air holes’ positions, radii, alignments, and surface roughness, among other Factors. It is revealed that the Q-factor decreases significantly from an ideally designed value due to such imperfections, with the main influence being the asymmetric alignment of the air hole line relative to the center of the nanobeam in the currently used fabrication process. Our analysis provides important information for achieving higher Q-Factors in the cavities.

  • symmetrically glass clad photonic crystal nanocavities with ultrahigh Quality Factors
    Optics Letters, 2011
    Co-Authors: Bongshik Song, Seungwoo Jeon, Susumu Noda
    Abstract:

    We design and fabricate ultra-high-Quality (Q) photonic nanocavities in a symmetrically glass-clad silicon (Si) two-dimensional (2D) photonic crystal (PhC) structure. We theoretically investigate the dependence of the refractive index of the glass on the Q Factors for asymmetric and symmetric structures. We show that the index-symmetric distribution of the glass is a critical factor to realize ultrahigh Q Factors for glass-clad 2D PhC structures. We fabricate symmetrically glass-clad Si PhC nanocavities and achieve a record Q factor of 1×106, comparable with the highest Q Factors of nanocavities in air-bridge structures.

  • reflectance measurement of two dimensional photonic crystal nanocavities with embedded Quantum dots
    Physical Review B, 2010
    Co-Authors: W C Stumpf, Takashi Asano, T Kojima, Masayuki Fujita, Yoshiya Tanaka, Susumu Noda
    Abstract:

    The spectra of two-dimensional photonic crystal slab nanocavities with embedded InAs Quantum dots are measured by photoluminescence and reflectance. In comparing the spectra taken by these two different methods, consistency with the nanocavities' resonant wavelengths is found. Furthermore, it is shown that the reflectance method can measure both active and passive cavities. Q-Factors of nanocavities, whose resonant wavelengths range from 1280 to 1620 nm, are measured by the reflectance method in cross polarization. Experimentally, Q-Factors decrease for longer wavelengths and the intensity, reflected by the nanocavities on resonance, becomes minimal around 1370 nm. The trend of the Q-Factors is explained by the change of the slab thickness relative to the resonant wavelength, showing a good agreement between theory and experiment. The trend of reflected intensity by the nanocavities on resonance can be understood as effects that originate from the PC slab and the underlying air cladding thickness. In addition to three dimensional finite-difference time-domain calculations, an analytical model is introduced that is able to reproduce the wavelength dependence of the reflected intensity observed in the experiment.

  • dynamic increase and decrease of photonic crystal nanocavity Q Factors for optical pulse control
    Optics Express, 2008
    Co-Authors: Jeremy Upham, Yoshinori Tanaka, Takashi Asano, Susumu Noda
    Abstract:

    We introduce recent advances in dynamic control over the Q factor of a photonic crystal nanocavity system. By carefully timing a rapid increase of the Q factor from 3800 to 22,000, we succeed in capturing a 4ps signal pulse within the nanocavity with a photon lifetime of 18ps. By performing an additional transition of the Q factor within the photon lifetime, the held light is once again ejected from of the system on demand.

Marko Loncar - One of the best experts on this subject based on the ideXlab platform.

  • high Q chaotic lithium niobate microdisk cavity
    Optics Letters, 2018
    Co-Authors: Li Wang, Marko Loncar, Qihuang Gong, Cheng Wang, Jie Wang, Fang Bo, Mian Zhang, Yunfeng Xiao
    Abstract:

    Lithium niobate (LN) is the workhorse for modern optoelectronics industry and nonlinear optics. High Quality (Q) factor LN microresonators are promising candidates for applications in optical communications, Quantum photonics, and sensing. However, the phase-matching reQuirement of traditional evanescent coupling methods poses significant challenges to achieve high coupling efficiencies of the pump and signal light simultaneously, ultimately limiting the practical usefulness of these high Q factor LN resonators. Here, for the first time, to the best of our knowledge, we demonstrate deformed chaotic LN microcavities that feature directional emission patterns and high Q Factors simultaneously. The chaotic LN microdisks are created using conventional semiconductor fabrication processes, with measured Q Factors exceeding 106 in the telecommunication band. We show that our devices can be free-space-coupled with high efficiency by leveraging directional emission from the asymmetric cavity. Using this broadband approach, we demonstrate a 58-fold enhancement of free-space collection efficiency of a second harmonic generation signal, compared with a circular microdisk.

  • high Q optical nanocavities in bulk single crystal diamond
    Conference on Lasers and Electro-Optics, 2014
    Co-Authors: Michael J Burek, Yiwen Chu, Madelaine S Z Liddy, Parth Patel, Jake Rochman, Mikhail D Lukin, Marko Loncar
    Abstract:

    Optical nanocavities (racetrack resonators and photonic crystal cavities) are fabricated in bulk single-crystal diamond via angled-etching. Devices operating in the telecom band exhibited Q-Factors exceeding 10^5, while devices in the visible yielded Q-Factors approaching 10^4.

  • Integrated high-Quality factor silicon-on-sapphire resonators for mid-infrared applications
    CLEO: 2013, 2013
    Co-Authors: Raji Shankar, Man Bulu, Marko Loncar
    Abstract:

    We demonstrate high-Quality (Q) factor grating-coupled silicon-on-sapphire ring resonators, operating around 4.5 μm. Total Q-Factors of 151,000 and intrinsic Q-Factors of 278,000 are measured, enabling applications in nonlinear wavelength generation and other areas.

  • integrated high Quality factor silicon on sapphire ring resonators for the mid infrared
    Applied Physics Letters, 2013
    Co-Authors: Raji Shankar, Irfan Bulu, Marko Loncar
    Abstract:

    We demonstrate high-Quality (Q) factor grating-coupled ring resonators in a silicon-on-sapphire platform, operating at wavelengths between 4.3 and 4.6 μm. Total Q-Factors of 151 000 and intrinsic Q-Factors of 278 000 are measured, representing the highest Q-Factors measured at the mid-infrared in Si.

  • Integrated high-Quality factor silicon-on-sapphire ring resonators for the mid-infrared
    10th International Conference on Group IV Photonics, 2013
    Co-Authors: Raji Shankar, Irfan Bulu, Marko Loncar
    Abstract:

    We demonstrate high-Quality (Q) factor grating-coupled silicon-on-sapphire ring resonators, operating around 4.5 μm. Total Q-Factors of 151,000 and intrinsic Q-Factors of 278,000 are measured, enabling applications in nonlinear wavelength generation and other areas.

Lute Maleki - One of the best experts on this subject based on the ideXlab platform.

Takashi Asano - One of the best experts on this subject based on the ideXlab platform.

  • sub 100 nw threshold raman silicon laser designed by a machine learning method that optimizes the product of the cavity Q Factors
    Optics Express, 2021
    Co-Authors: Taro Kawakatsu, Susumu Noda, Takashi Asano, Yasushi Takahashi
    Abstract:

    Raman silicon lasers based on photonic crystal nanocavities with a threshold of several hundred microwatts for continuous-wave lasing have been realized. In particular, the threshold depends on the degree of confinement of the excitation light and the Raman scattering light in the two nanocavity modes. Here, we report lower threshold values for Raman silicon nanocavity lasers achieved by increasing the Quality (Q) Factors of the two cavity modes. By using an optimization method based on machine learning, we first increase the product of the two theoretical Q values by a factor of 17.0 compared to the conventional cavity. The experimental evaluation demonstrates that, on average, the actually achieved product is more than 2.5 times larger than that of the conventional cavity. The input–output characteristic of a Raman laser with a threshold of 90 nW is presented and the lowest threshold obtained in our experiments is 40 nW.

  • analysis of Q Factors of structural imperfections in triangular cross section nanobeam photonic crystal cavities
    Journal of The Optical Society of America B-optical Physics, 2015
    Co-Authors: Yuki Yamaguchi, Seungwoo Jeon, Bongshik Song, Takashi Asano, Yoshinori Tanaka, Susumu Noda
    Abstract:

    We present comprehensive and Quantitative analysis of the effect of structural imperfections on Quality (Q)-Factors in triangular cross-section nanobeam photonic crystal cavities. We investigated statistically the optical losses due to the various imperfections in the air holes’ positions, radii, alignments, and surface roughness, among other Factors. It is revealed that the Q-factor decreases significantly from an ideally designed value due to such imperfections, with the main influence being the asymmetric alignment of the air hole line relative to the center of the nanobeam in the currently used fabrication process. Our analysis provides important information for achieving higher Q-Factors in the cavities.

  • reflectance measurement of two dimensional photonic crystal nanocavities with embedded Quantum dots
    Physical Review B, 2010
    Co-Authors: W C Stumpf, Takashi Asano, T Kojima, Masayuki Fujita, Yoshiya Tanaka, Susumu Noda
    Abstract:

    The spectra of two-dimensional photonic crystal slab nanocavities with embedded InAs Quantum dots are measured by photoluminescence and reflectance. In comparing the spectra taken by these two different methods, consistency with the nanocavities' resonant wavelengths is found. Furthermore, it is shown that the reflectance method can measure both active and passive cavities. Q-Factors of nanocavities, whose resonant wavelengths range from 1280 to 1620 nm, are measured by the reflectance method in cross polarization. Experimentally, Q-Factors decrease for longer wavelengths and the intensity, reflected by the nanocavities on resonance, becomes minimal around 1370 nm. The trend of the Q-Factors is explained by the change of the slab thickness relative to the resonant wavelength, showing a good agreement between theory and experiment. The trend of reflected intensity by the nanocavities on resonance can be understood as effects that originate from the PC slab and the underlying air cladding thickness. In addition to three dimensional finite-difference time-domain calculations, an analytical model is introduced that is able to reproduce the wavelength dependence of the reflected intensity observed in the experiment.

  • dynamic increase and decrease of photonic crystal nanocavity Q Factors for optical pulse control
    Optics Express, 2008
    Co-Authors: Jeremy Upham, Yoshinori Tanaka, Takashi Asano, Susumu Noda
    Abstract:

    We introduce recent advances in dynamic control over the Q factor of a photonic crystal nanocavity system. By carefully timing a rapid increase of the Q factor from 3800 to 22,000, we succeed in capturing a 4ps signal pulse within the nanocavity with a photon lifetime of 18ps. By performing an additional transition of the Q factor within the photon lifetime, the held light is once again ejected from of the system on demand.

  • analysis of the experimental Q Factors 1 million of photonic crystal nanocavities
    Optics Express, 2006
    Co-Authors: Takashi Asano, Bongshik Song, Susumu Noda
    Abstract:

    In this letter, we show that the Q Factors of the latest high-Q cavities in two dimensional photonic crystals, measured experimentally to be ~1000000, are determined by losses due to imperfections in the fabricated structures, and not by the cavity design. Quantitative analysis shows that the dominant sources of loss include the tilt of air-holes within the cavity, the roughness of the inner walls of the air-holes, variation in the radii of the air-holes, and optical absorption by adsorbed material. We believe that cavities with experimental Q Factors of the order of several millions will be obtained in the future by reducing the losses due to imperfections through improved fabrication techniQues.

Vladimir S. Ilchenko - One of the best experts on this subject based on the ideXlab platform.