The Experts below are selected from a list of 26943 Experts worldwide ranked by ideXlab platform
Denis R. Hall - One of the best experts on this subject based on the ideXlab platform.
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Dual-Axis beam correction for an array of single-mode diode laser emitters using a laser-written custom phase-plate
Optics express, 2009Co-Authors: Natalia Trela, J. J. Wendland, Howard J. Baker, Denis R. HallAbstract:A single optical component for a diode laser bar combines Fast-Axis smile and lens error correction with slow-Axis collimation. Produced by laser-machining/polishing, it provides 0.9mm focal length, 200μm pitch slow-Axis collimation on the same surface that corrects Fast-Axis errors. Custom fabrication enables fill-factor optimization for the 49 single-mode beams and gives parallel collimation with rms pointing errors of 3% and 6% of the far-field divergence for the Fast- and slow-Axis array respectively. Sub-micron pitch mismatch between the slow-Axis lens and emitter arrays, and beam pointing changes by thermal expansion of the laser bar are detected.
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Low-loss wavelength locking of a 49-element single mode diode laser bar with phase-plate beam correction
CLEO Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009Co-Authors: Natalia Trela, Roy Mcbride, Howard J. Baker, Denis R. HallAbstract:In previous work on laser diode optics, we have used laser-written phase-plates to correct the fabrication and Fast-Axis collimation errors of diode laser bars and produce a restoration of brightness of up to a factor of 10. Recently, we extended the technique to provide both Fast-Axis correction and slow-Axis collimation in a single element, applied to an array of 10 tapered emitters with a 100µm pitch [1]. Here we report the use of dual-Axis correction for a full-length diode bar from Bookham, with 49 single mode emitters and 30W cw output at 975 nm. Fast-Axis smile and lens error correction is combined with laser-cut slow Axis collimation to give highly parallel beams with far-field divergence of 2.6mrad (Fast Axis) and 13mrad (slow-Axis). Fig 1 shows the improvement in Fast-Axis divergence, in the form of far-field pattern vs. emitter number.
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Correction of beam errors in high power laser diode bars and stacks.
Optics express, 2006Co-Authors: J. F. Monjardin, Howard J. Baker, Krzysztof M. Nowak, Denis R. HallAbstract:The beam errors of an 11 bar laser diode stack fitted with Fast-Axis collimator lenses have been corrected by a single refractive plate, produced by laser cutting and polishing. The so-called smile effect is virtually eliminated and collimator aberration greatly reduced, improving the Fast-Axis beam quality of each bar by a factor of up to 5. The single corrector plate for the whole stack ensures that the radiation from all the laser emitters is parallel to a common Axis. Beam-pointing errors of the bars have been reduced to below 0.7 mrad.
Huaiyu Yuan - One of the best experts on this subject based on the ideXlab platform.
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stratified seismic anisotropy and the lithosphere asthenosphere boundary beneath eastern north america
Journal of Geophysical Research, 2014Co-Authors: Huaiyu Yuan, Vadim LevinAbstract:Long records of teleseismic observations accumulated at permanent seismic stations Harvard, MA; Palisades, NY; and Standing Stone, PA, in eastern North America are inverted for vertical distribution of anisotropic parameters. High-resolution anisotropy-aware P wave receiver function analysis and multiple-layer core-refracted SKS waveform modeling favor more than one layer of anisotropy beneath all sites. Our analyses suggest that the depth sensitivity to stratified anisotropic seismic velocity in converted phases and the SKS waveforms are complementary and confirm that these two approaches yield consistent lithospheric anisotropic Fast Axis directions. We illustrate the feasibility of the lithosphere-asthenosphere boundary detection on a regional scale through anisotropy-aware receiver functions. Joint interpretation of receiver functions and SKS waveforms beneath eastern North America suggests a thin (~100 km) anisotropic lithosphere with Fast Axis orientation nearly orthogonal to the strike of major tectonic units and an underlying anisotropic asthenosphere with Fast Axis directions that favor the HS3-NUVEL 1A plate motion model. Consistent lithospheric anisotropy inferred from both techniques suggests broad presence of coherent fabric in the lower lithosphere, possibly developed in a regional scale delamination event after the assembly of Appalachians.
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On the interpretation of SKS splitting measurements in the presence of several layers of anisotropy
Geophysical Journal International, 2012Co-Authors: Barbara Romanowicz, Huaiyu YuanAbstract:SUMMARY Concerns over the validity of expressions derived by Montagner et al. that link SKS splitting measurements to the variation with depth of anisotropic parameters in the upper mantle have been recently expressed, pointing out that the long period approximations applied by these authors may not be valid for the frequency range commonly used in SKS studies, and in particular, that the anisotropy splitting parameters should depend on the order in which different anisotropy layers are arranged with depth. We show here that indeed, measurements of splitting time and Fast Axis direction performed at individual azimuths do depend on the order of layering, however, the expressions of Montagner et al. concern station-averaged quantities that do not depend on the order of layers. It is therefore correct to use these expressions in joint inversions of surface waveforms and SKS station-averaged splitting measurements. On the other hand, the depth-dependent sensitivity of surface waveforms naturally provides constraints on the order of layering. Having clarified this confusion, we extend the expressions of Montagner et al. to the case of a tilted Axis of symmetry and non-vertical incident waves, and show that station-averaged estimates of ‘effective’ splitting parameters: splitting time, Fast Axis direction and tilt of the Fast Axis, can be related to the integral with depth of quantities, which now depend not only on the local splitting time and Fast Axis direction, but also on the local tilt of the Fast Axis, thus providing constraints also on the variation of the tilt with depth. We show that the effective parameters used as constraints in the inversion can be obtained either from the measurement of splitting intensity, or through a parameter search and cross-convolution method. In particular, in the case when the effective tilt is significant, the splitting intensity no longer presents 180° periodicity with azimuth, providing a diagnostic tool for the presence of such tilts in the upper mantle. Thus, combining body-wave and surface wave observations also has the potential of constraining the variation with depth of the tilt of the Fast Axis of anisotropy, a geodynamically important parameter.
Howard J. Baker - One of the best experts on this subject based on the ideXlab platform.
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Monolithic Fast-Axis collimation of diode laser stacks
High-Power Diode Laser Technology and Applications XI, 2013Co-Authors: Roy Mcbride, Natalia Trela, Matthew Oren Currie, J. J. Wendland, Howard J. BakerAbstract:Commercially-available QCW diode laser stacks with bar pitch below 0.5mm can now deliver source power densities exceeding 10kW/cm2. An increasing number of applications for these sources also specify high brightness, with collimation requirements ranging from equalization of Fast and slow Axis divergence to achieving Fast-Axis divergence within a small multiple of the diffraction limit. While collimation can be achieved by mounting an array of rod lenses in a frame with a suitable v-groove array, the resulting optical assembly has a large number of elements and associated adhesive bonds, and the size of the mounting frame limits the density at which stacks can be packed together. We present results exploiting an alternative approach using monolithic Fast-Axis collimator arrays. This approach greatly reduces the component count and minimizes the number of adhesive bonds required, providing a compact and rugged assembly well-suited to demanding applications. The monolithic collimator array also simplifies package design, and maximizes the achievable device stack packing density. Lens array properties may be tailored to generate applicationspecific divergence profiles or to match the geometry of individual stacks in order to achieve low divergence. Directwrite fabrication of these components allows mass-customization, offering a scalable, low-cost route to high volume collimation for fusion applications.
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Dual-Axis beam correction for an array of single-mode diode laser emitters using a laser-written custom phase-plate
Optics express, 2009Co-Authors: Natalia Trela, J. J. Wendland, Howard J. Baker, Denis R. HallAbstract:A single optical component for a diode laser bar combines Fast-Axis smile and lens error correction with slow-Axis collimation. Produced by laser-machining/polishing, it provides 0.9mm focal length, 200μm pitch slow-Axis collimation on the same surface that corrects Fast-Axis errors. Custom fabrication enables fill-factor optimization for the 49 single-mode beams and gives parallel collimation with rms pointing errors of 3% and 6% of the far-field divergence for the Fast- and slow-Axis array respectively. Sub-micron pitch mismatch between the slow-Axis lens and emitter arrays, and beam pointing changes by thermal expansion of the laser bar are detected.
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Low-loss wavelength locking of a 49-element single mode diode laser bar with phase-plate beam correction
CLEO Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009Co-Authors: Natalia Trela, Roy Mcbride, Howard J. Baker, Denis R. HallAbstract:In previous work on laser diode optics, we have used laser-written phase-plates to correct the fabrication and Fast-Axis collimation errors of diode laser bars and produce a restoration of brightness of up to a factor of 10. Recently, we extended the technique to provide both Fast-Axis correction and slow-Axis collimation in a single element, applied to an array of 10 tapered emitters with a 100µm pitch [1]. Here we report the use of dual-Axis correction for a full-length diode bar from Bookham, with 49 single mode emitters and 30W cw output at 975 nm. Fast-Axis smile and lens error correction is combined with laser-cut slow Axis collimation to give highly parallel beams with far-field divergence of 2.6mrad (Fast Axis) and 13mrad (slow-Axis). Fig 1 shows the improvement in Fast-Axis divergence, in the form of far-field pattern vs. emitter number.
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High-power, low-divergence, linear array of quasi-diffraction-limited beams supplied by tapered diodes
Applied optics, 2007Co-Authors: Gilbert L. Bourdet, Roy Mcbride, Howard J. Baker, Imen Hassiaoui, J. F. Monjardin, Nicolas Michel, Michel KrakowskiAbstract:We describe for the first time to our knowledge the performance for a linear array of tapered laser diodes with both Fast- and slow-Axis collimation using a microlens for Fast-Axis collimation and a laser-written phase plate for slow-Axis collimation and correction of the residual Fast-Axis errors from lens aberrations, thermal lensing, astigmatism, pointing errors, and other wavefront distortions. The phase plate leads to M2 factor reductions of 1.5 for the lensed array following the Fast Axis and 2.6 for the whole bar following the slow Axis.
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Correction of beam errors in high power laser diode bars and stacks.
Optics express, 2006Co-Authors: J. F. Monjardin, Howard J. Baker, Krzysztof M. Nowak, Denis R. HallAbstract:The beam errors of an 11 bar laser diode stack fitted with Fast-Axis collimator lenses have been corrected by a single refractive plate, produced by laser cutting and polishing. The so-called smile effect is virtually eliminated and collimator aberration greatly reduced, improving the Fast-Axis beam quality of each bar by a factor of up to 5. The single corrector plate for the whole stack ensures that the radiation from all the laser emitters is parallel to a common Axis. Beam-pointing errors of the bars have been reduced to below 0.7 mrad.
Natalia Trela - One of the best experts on this subject based on the ideXlab platform.
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Monolithic Fast-Axis collimation of diode laser stacks
High-Power Diode Laser Technology and Applications XI, 2013Co-Authors: Roy Mcbride, Natalia Trela, Matthew Oren Currie, J. J. Wendland, Howard J. BakerAbstract:Commercially-available QCW diode laser stacks with bar pitch below 0.5mm can now deliver source power densities exceeding 10kW/cm2. An increasing number of applications for these sources also specify high brightness, with collimation requirements ranging from equalization of Fast and slow Axis divergence to achieving Fast-Axis divergence within a small multiple of the diffraction limit. While collimation can be achieved by mounting an array of rod lenses in a frame with a suitable v-groove array, the resulting optical assembly has a large number of elements and associated adhesive bonds, and the size of the mounting frame limits the density at which stacks can be packed together. We present results exploiting an alternative approach using monolithic Fast-Axis collimator arrays. This approach greatly reduces the component count and minimizes the number of adhesive bonds required, providing a compact and rugged assembly well-suited to demanding applications. The monolithic collimator array also simplifies package design, and maximizes the achievable device stack packing density. Lens array properties may be tailored to generate applicationspecific divergence profiles or to match the geometry of individual stacks in order to achieve low divergence. Directwrite fabrication of these components allows mass-customization, offering a scalable, low-cost route to high volume collimation for fusion applications.
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Dual-Axis beam correction for an array of single-mode diode laser emitters using a laser-written custom phase-plate
Optics express, 2009Co-Authors: Natalia Trela, J. J. Wendland, Howard J. Baker, Denis R. HallAbstract:A single optical component for a diode laser bar combines Fast-Axis smile and lens error correction with slow-Axis collimation. Produced by laser-machining/polishing, it provides 0.9mm focal length, 200μm pitch slow-Axis collimation on the same surface that corrects Fast-Axis errors. Custom fabrication enables fill-factor optimization for the 49 single-mode beams and gives parallel collimation with rms pointing errors of 3% and 6% of the far-field divergence for the Fast- and slow-Axis array respectively. Sub-micron pitch mismatch between the slow-Axis lens and emitter arrays, and beam pointing changes by thermal expansion of the laser bar are detected.
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Low-loss wavelength locking of a 49-element single mode diode laser bar with phase-plate beam correction
CLEO Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009Co-Authors: Natalia Trela, Roy Mcbride, Howard J. Baker, Denis R. HallAbstract:In previous work on laser diode optics, we have used laser-written phase-plates to correct the fabrication and Fast-Axis collimation errors of diode laser bars and produce a restoration of brightness of up to a factor of 10. Recently, we extended the technique to provide both Fast-Axis correction and slow-Axis collimation in a single element, applied to an array of 10 tapered emitters with a 100µm pitch [1]. Here we report the use of dual-Axis correction for a full-length diode bar from Bookham, with 49 single mode emitters and 30W cw output at 975 nm. Fast-Axis smile and lens error correction is combined with laser-cut slow Axis collimation to give highly parallel beams with far-field divergence of 2.6mrad (Fast Axis) and 13mrad (slow-Axis). Fig 1 shows the improvement in Fast-Axis divergence, in the form of far-field pattern vs. emitter number.
Peiyun Cheng - One of the best experts on this subject based on the ideXlab platform.
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Numerical simulations of Fast-Axis instability of vector solitons in mode-locked fiber lasers.
Optics express, 2017Co-Authors: Xuewen Shu, Peiyun ChengAbstract:We demonstrate the Fast-Axis instability in mode-locked fiber lasers numerically for the first time. We find that the energy of the Fast mode will be transferred to the slow mode when the strong pump strength makes the soliton period short. A nearly linearly polarized vector soliton along the slow-Axis could be generated under certain cavity parameters. The final polarization of the vector soliton is related to the initial polarization of the seed pulse. Two regimes of energy exchanging between the slow mode and the Fast mode are explored and the direction of the energy flow between two modes depends on the phase difference. The dip-type sidebands are found to be intrinsic characteristics of the mode-locked fiber lasers under high pulse energy.
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Vector solitons in mode-locked fiber lasers by Fast-Axis instability
2017 Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR), 2017Co-Authors: Xuewen Shu, Peiyun ChengAbstract:Fast-Axis instability in mode-locked fiber lasers is demonstrated numerically. The Fast-Axis instability manifests as the Fast mode transferring its energy to the slow mode when the pulse energy is strong enough. The instability is caused by the strong nonlinear birefringence compensating for the linear birefringence.