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Kenju Otsuka - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic characterization of beating sinusoidal wave oscillations in a thin-slice solid-State Laser with coupled orthogonally polarized transverse modes
    arXiv: Optics, 2019
    Co-Authors: Kenju Otsuka
    Abstract:

    Dynamic characterization of self-induced beating sinusoidal wave (BSW) oscillations and related phenomena, which were previously explored in a thin-slice dual-polarization solid-State Laser operating in the regime of incomplete mode-locking of orthogonally polarized transverse eigenmodes, namely, a quasi-locked State [Laser Physics Letters, 15 (2018) 075001], is performed in terms of the amplitude correlation coefficient and intensity circulation among various orthogonally polarized mode pairs. Polarization-dependent symmetry-breaking featuring a nonreciprocal intensity flow for different orthogonally polarized mode pairs operating in the BSW State are found. The singular State is hidden in a nonlinear system where a perfect mode-locked BSW State with a large amplitude correlation coefficient featuring reciprocal intensity flow is established for a transverse mode pair possessing particular polarization directions that are related to the intensity ratio of orthogonally polarized transverse eigenmodes. Self-organized chaos synchronization is shown to take place for such a singular transverse mode pair subjected to self-mixing modulations.

  • Measurements of liquid surface fluctuations using a self-mixing solid-State Laser
    Journal of Applied Physics, 2014
    Co-Authors: S. Sudo, Kenju Otsuka
    Abstract:

    We propose a highly sensitive method for measurements of liquid surface fluctuations with nanometer-order displacement using a self-mixing Laser Doppler velocimeter (LDV) comprising a Laser-diode-pumped thin-slice solid-State Laser and a simple photodiode. In this measurement system, the scattered light from the liquid surface is reinjected into the solid-State Laser, and then the Laser output from the solid-State Laser is modulated by this reinjected Laser light. The time dependence of the displacement of liquid surface fluctuations can be obtained from the analysis of the modulated Laser output. We describe various measuring methods and the optical system of the self-mixing LDV for real-time measurements of liquid surface fluctuations. Real-time measurement of liquid surface fluctuations can be performed with high amplitude and frequency resolutions by the analysis of the modulated Laser output.

  • easy measurement and analysis method of zeta potential and electrophoretic mobility of water dispersed colloidal particles by using a self mixing solid State Laser
    Journal of Applied Physics, 2013
    Co-Authors: S. Sudo, T Ohtomo, Kenju Otsuka
    Abstract:

    We describe a highly sensitive method of measuring electrophoretic mobility and zeta potential of water-dispersed colloidal particles by using a self-mixing Laser Doppler velocimeter with a Laser-diode-pumped, thin-slice solid-State Laser with extremely high optical sensitivity. The power spectra of Laser output modulated by reinjected Laser light scattered by the electrophoretic particles were observed. The power spectrum cannot be described by the well-known formula for translational motion or flowing Brownian motion, i.e., a combination of Doppler shift, diffusion, and translation. The power spectra shape is found to reflect the velocity distribution of electrophoretic particles in a capillary tube due to the electro-osmotic flow contribution. Not only evaluation of the electrophoretic mobility and zeta potential but also the particle diameter undergoing electrophoretic motion can be performed from the shape of the power spectrum.

  • generation of vortex array beams from a thin slice solid State Laser with shaped wide aperture Laser diode pumping
    Optics Letters, 2009
    Co-Authors: Kenju Otsuka, Shu Chun Chu
    Abstract:

    We demonstrate vortex array-beam generations from a thin-slice, wide-aperture, solid-State Laser with Laser-diode end-pumping. Radial and rectangular vortex arrays were found to be formed in a controlled fashion with symmetric and asymmetric pump-beam profiles, respectively. Most of these vortices exhibited single-frequency oscillations arising from a spontaneous process of transverse mode locking of degenerate or nearly degenerate modes assisted by the Laser nonlinearity. Single-frequency rectangular array beams consisting of a large number of vortices, e.g., closely packed 25, 36, or 46 vortex pixels, were generated, originating from Ince–Gaussian modes excited by the asymmetric pumping.

  • real time nanometer vibration measurement with a self mixing microchip solid State Laser
    Optics Letters, 2002
    Co-Authors: Kenju Otsuka, Jingyuan Ko
    Abstract:

    Nanometer vibration analysis of a target has been demonstrated by a self-aligned optical feedback vibrometry technique that uses a Laser-diode-pumped microchip solid-State Laser. The Laser output waveform, which was modulated through interference between a lasing field and an extremely weak <-100‐dB frequency-modulated (FM) feedback field, was analyzed by the Hilbert transformation to yield the vibration waveform of the target. Experimental signal characteristics have been reproduced by numerical simulations. Real-time vibration measurement has also been achieved with a simple FM demodulation circuit.

U Keller - One of the best experts on this subject based on the ideXlab platform.

  • watt level 10 gigahertz solid State Laser enabled by self defocusing nonlinearities in an aperiodically poled crystal
    Nature Communications, 2017
    Co-Authors: Aline S Mayer, C R Phillips, U Keller
    Abstract:

    Femtosecond modelocked Lasers with multi-gigahertz pulse repetition rates are attractive sources for all applications that require individually resolvable frequency comb lines or high sampling rates. However, the modelocked Laser architectures demonstrated so far have several issues, including the need for single-mode pump Lasers, limited output power, Q-switching instabilities and challenging cavity geometries. Here, we introduce a technique that solves these issues. In a two-dimensionally patterned quasi-phase-matching (QPM) device, we create a large, low-loss self-defocusing nonlinearity, which simultaneously provides SESAM-assisted soliton modelocking in the normal dispersion regime and suppresses Q-switching induced damage. We demonstrate femtosecond passive modelocking at 10-GHz pulse repetition rates from a simple straight Laser cavity, directly pumped by a low-cost highly spatially multimode pump diode. The 10.6-GHz Yb:CaGdAlO4 (Yb:CALGO) Laser delivers 166-fs pulses at 1.2 W of average output power. This enables a new class of femtosecond modelocked diode-pumped solid-State Lasers with repetition rates at 10 GHz and beyond. Ultrafast Lasers with multi-gigahertz repetition rates are desirable for applications requiring high sampling rates or resolvable frequency comb lines. Here, Mayer et al. use cascading of quadratic nonlinearities to passively modelock a femtosecond solid-State Laser at a repetition rate of 10 GHz.

  • gigahertz frequency comb from a diode pumped solid State Laser
    Optics Express, 2014
    Co-Authors: Alexander Klenner, T Sudmeyer, Stephane Schilt, U Keller
    Abstract:

    We present the first stabilization of the frequency comb offset from a diode-pumped gigahertz solid-State Laser oscillator. No additional external amplification and/or compression of the output pulses is required. The Laser is reliably modelocked using a SESAM and is based on a diode-pumped Yb:CALGO gain crystal. It generates 1.7-W average output power and pulse durations as short as 64 fs at a pulse repetition rate of 1 GHz. We generate an octave-spanning supercontinuum in a highly nonlinear fiber and use the standard f-to-2f carrier-envelope offset (CEO) frequency fCEO detection method. As a pump source, we use a reliable and cost-efficient commercial diode Laser. Its multi-spatial-mode beam profile leads to a relatively broad frequency comb offset beat signal, which nevertheless can be phase-locked by feedback to its current. Using improved electronics, we reached a feedback-loop-bandwidth of up to 300 kHz. A combination of digital and analog electronics is used to achieve a tight phase-lock of fCEO to an external microwave reference with a low in-loop residual integrated phase-noise of 744 mrad in an integration bandwidth of [1 Hz, 5 MHz]. An analysis of the Laser noise and response functions is presented which gives detailed insights into the CEO stabilization of this frequency comb.

  • femtosecond diode pumped solid State Laser with a repetition rate of 4 8 ghz
    Optics Express, 2012
    Co-Authors: S Pekarek, Alexander Klenner, T Sudmeyer, Christian Fiebig, K Paschke, G Erbert, U Keller
    Abstract:

    We report on a diode-pumped Yb:KGW (ytterbium-doped potassium gadolinium tungState) Laser with a repetition rate of 4.8 GHz and a pulse duration of 396 fs. Stable fundamental modelocking is achieved with a semiconductor saturable absorber mirror (SESAM). The average output power of this compact diode-pumped solid State Laser is 1.9 W which corresponds to a peak power of 0.9 kW and the optical-to-optical efficiency is 36%. To the best of our knowledge, this is the femtosecond DPSSL with the highest repetition rate ever reported so far.

  • fully stabilized optical frequency comb with sub radian ceo phase noise from a sesam modelocked 1 5 µm solid State Laser
    Optics Express, 2011
    Co-Authors: Stephane Schilt, S Pekarek, T Sudmeyer, Vladimir Dolgovskiy, Nikola Bucalovic, Gianni Di Domenico, M C Stumpf, A E H Oehler, C Schori, U Keller
    Abstract:

    We report the first full stabilization of an optical frequency comb generated from a femtosecond diode-pumped solid-State Laser (DPSSL) operating in the 1.5-μm spectral region. The stability of the comb is characterized in free-running and in phase-locked operation by measuring the noise properties of the carrier-envelope offset (CEO) beat, of the repetition rate, and of a comb line at 1558 nm. The high Q-factor of the semiconductor saturable absorber mirror (SESAM)-modelocked 1.5-µm DPSSL results in a low-noise CEO-beat, for which a tight phase lock can be much more easily realized than for a fiber comb. Using a moderate feedback bandwidth of only 5.5 kHz, we achieved a residual integrated phase noise of 0.72 rad rms for the locked CEO, which is one of the smallest values reported for a frequency comb system operating in this spectral region. The fractional frequency stability of the CEO-beat is 20‑fold better than measured in a standard self-referenced commercial fiber comb system and contributes only 10−15 to the optical carrier frequency instability at 1 s averaging time.

  • self referencable frequency comb from a 170 fs 1 5 μm solid State Laser oscillator
    Applied Physics B, 2010
    Co-Authors: M C Stumpf, S Pekarek, T Sudmeyer, A E H Oehler, J M Dudley, U Keller
    Abstract:

    We report measurement of the first carrier-envelope offset (CEO) frequency signal from a spectrally broadened ultrafast solid-State Laser oscillator operating in the 1.5 μm spectral region. The f-to-2f CEO frequency beat signal is 49 dB above the noise floor (100-kHz resolution bandwidth) and the free-running linewidth of 3.6 kHz is significantly better than typically obtained by ultrafast fiber Laser systems. We used a SESAM mode-locked Er:Yb:glass Laser generating 170-fs pulses at a 75 MHz pulse repetition rate with 110-mW average power. It is pumped by one standard telecom-grade 980-nm diode consuming less than 1.5 W of electrical power. Without any further pulse compression and amplification, a coherent octave-spanning frequency comb is generated in a polarization-maintaining highly-nonlinear fiber (PM-HNLF). The fiber length was optimized to yield a strong CEO frequency beat signal between the outer Raman soliton and the spectral peak of the dispersive wave within the supercontinuum. The polarization-maintaining property of the supercontinuum fiber was crucial; comparable octave-spanning supercontinua from two non-PM fibers showed higher intensity noise and poor coherence. A stable CEO-beat was observed even with pulse durations above 200 fs. Achieving a strong CEO frequency signal from relatively long pulses with moderate power levels substantially relaxes the demands on the driving Laser, which is particularly important for novel gigahertz diode-pumped solid-State and semiconductor Lasers.

H.p. Weber - One of the best experts on this subject based on the ideXlab platform.

  • Thermal effects in solid-State Laser materials
    Optical Materials, 1998
    Co-Authors: R. Weber, B. Neuenschwander, H.p. Weber
    Abstract:

    Thermal effects in solid-State Laser materials are a critical issue for designing diode-pumped solid-State Lasers. An overview over temperature and stress distribution as well as their influence on the optical behavior is given. Basic analytical treatment of the rod geometry is compared with a more accurate Finite Element calculation for the case of a transversally diode-pumped Nd:YAG rod. Significant differences in the shape of the thermal lens are observed.

Alexander A Kaminskii - One of the best experts on this subject based on the ideXlab platform.

  • yb3 y2o3 ceramics a novel solid State Laser material
    Japanese Journal of Applied Physics, 2002
    Co-Authors: K Takaichi, T Uematsu, Akira Shirakawa, Mitsuru Musha, Kenichi Ueda, Hideki Yagi, Takagimi Yanagitani, Alexander A Kaminskii
    Abstract:

    A new solid-State Laser based on Yb3+-doped highly transparent nanocrystalline yttria (Y2O3) ceramics was developed. At room temperature and under a pump power of 2.63 W from a single InGaAs Laser diode at ≈ 0.94 µm, a continuous-wave Laser output of 0.47 W at 1.077 µm wavelength was obtained corresponding to a slope efficiency of about 32%. Some main spectroscopic properties of Yb3+:Y2O3 ceramics were also investigated.

  • neodymium doped yttrium aluminum garnet y3al5o12 nanocrystalline ceramics a new generation of solid State Laser and optical materials
    Journal of Alloys and Compounds, 2002
    Co-Authors: Jianren Lu, Kenichi Ueda, Hideki Yagi, Takagimi Yanagitani, Yasuhiro Akiyama, Alexander A Kaminskii
    Abstract:

    We have developed and adequately characterized a new generation of solid-State Laser and optical materials on the basis of highly transparent nanocrystalline yttrium aluminium garnet Y3Al5O12 (YAG) ceramics. We consider this new type of inorganic Laser media as an illustration of selected results of the latest investigations of Laser and spectroscopic parameters of nanocrystalline Nd3+:YAG ceramics. In particular, absorption, luminescence, stimulated Raman scattering properties, as well as highly efficient CW Laser oscillation at wavelength of 1064 nm under Laser-diode pumping were investigated. The results show that this new Laser material is a very good alternative to Nd3+:YAG single crystals. In particular, in preliminary comparison Laser experiments with both Nd3+:YAG ceramic and single-crystal rods, output powers of 88 W and 99 W were obtained corresponding to optical-to-optical efficiencies of 30% and 34% for ceramic and single crystal rods, respectively. A CW 1.46 kW high power Nd:YAG ceramic Laser was developed. Quite recently, Laser oscillation at ≈1.32 μm was also demonstrated.

R. Weber - One of the best experts on this subject based on the ideXlab platform.

  • Thermal effects in solid-State Laser materials
    Optical Materials, 1998
    Co-Authors: R. Weber, B. Neuenschwander, H.p. Weber
    Abstract:

    Thermal effects in solid-State Laser materials are a critical issue for designing diode-pumped solid-State Lasers. An overview over temperature and stress distribution as well as their influence on the optical behavior is given. Basic analytical treatment of the rod geometry is compared with a more accurate Finite Element calculation for the case of a transversally diode-pumped Nd:YAG rod. Significant differences in the shape of the thermal lens are observed.