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High power (>5 W) lambda ~9.6 um tapered quantum cascade lasers grown by OMVPE

Summary

AlInAS/GaInAs superlattices (SLs) with barrier and well layers of various thicknesses were grown by organometallic vapor phase epitaxy to optimize growth of quantum cascade lasers (QCLs). High-resolution x-ray diffraction data of nominally lattice-matched SLs show a systematic shift toward more compressively strained SLs as the barrier/well layer thicknesses are decreased below about 10 nm. This shift is attributed to In surface segregation in both AlInAs and GaInAs. This shift is compensated for in the growth of ultra-thin layers in QCL structures. QCLs with tapered gain regions and emitting at 9.6 um are demonstrated with peak power as high as 5.3 W from one facet at 20 degrees C.
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Summary

AlInAS/GaInAs superlattices (SLs) with barrier and well layers of various thicknesses were grown by organometallic vapor phase epitaxy to optimize growth of quantum cascade lasers (QCLs). High-resolution x-ray diffraction data of nominally lattice-matched SLs show a systematic shift toward more compressively strained SLs as the barrier/well layer thicknesses are decreased...

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High-power arrays of quantum cascade laser master-oscillator power-amplifiers

Published in:
Opt. Express, Vol. 21, No. 4, 25 February 2013, pp. 4518-4530.

Summary

We report on multi-wavelength arrays of master-oscillator power-amplifier quantum cascade lasers operating at wavelengths between 9.2 and 9.8 um. All elements of the high-performance array feature longitudinal (spectral) as well as transverse single-mode emission at peak powers between 2.7 and 10 W at room temperature. The performance of two arrays that are based on different seed-section designs is thoroughly studied and compared. High output power and excellent beam quality render the arrays highly suitable for stand-off spectroscopy applications.
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Summary

We report on multi-wavelength arrays of master-oscillator power-amplifier quantum cascade lasers operating at wavelengths between 9.2 and 9.8 um. All elements of the high-performance array feature longitudinal (spectral) as well as transverse single-mode emission at peak powers between 2.7 and 10 W at room temperature. The performance of two arrays...

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Development of adaptive liquid microlenses and microlens arrays

Published in:
SPIE Photonics West 2013: MOEMS-MEMS, 2-7 February 2013.

Summary

We report on the development of sub-millimeter size adaptive liquid microlenses and microlens arrays using two immiscible liquids to form individual lenses. Microlenses and microlens arrays having aperture diameters as small as 50 microns were fabricated on a planar quartz substrate using patterned hydrophobic/hydrophilic regions. Liquid lenses were formed by a self-assembled oil dosing process that created well-defined lenses having a high fill factor. Variable focus was achieved by controlling the lens curvature through electrowetting. Greater than 70 degrees of contact angle change was achieved with less than 20 volts, which results in a large optical power dynamic range.
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Summary

We report on the development of sub-millimeter size adaptive liquid microlenses and microlens arrays using two immiscible liquids to form individual lenses. Microlenses and microlens arrays having aperture diameters as small as 50 microns were fabricated on a planar quartz substrate using patterned hydrophobic/hydrophilic regions. Liquid lenses were formed by...

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Measurement of the surface-enhanced coherent anti-Stokes Raman scattering (SECARS) due to the 1574 cm^-1 surface-enhanced Raman scattering (SERS) mode of benzenethiol using low-power (<20 mW) CW diode lasers

Published in:
Appl. Spectrosc., Vol. 67, No. 2, February 2013, pp. 132-135.

Summary

The surface-enhanced coherent anti-Stokes Raman scattering (SECARS) from a self-assembled monolayer (SAM) of benzenethiol on a silver-coated surface-enhanced Raman scattering (SERS) substrate has been measured for the 1574 cm^-1 SERS mode. A value of 9.6 +- 1.7 x 10^-14 W was determined for the resonant component of the SECARS signal using 17.8 mW of 784.9 nm pump laser power and 7.1 mW of 895.5 nm Stokes laser power; the pump and Stokes lasers were polarized parallel to each other but perpendicular to the grooves of the diffraction grating in the spectrometer. The measured value of resonant component of the SECARS signal is in agreement with the calculated value of 9.3 x 10^-14 W using the measured value of 8.7 +- 0.5 cm^-1 for the SERS linewidth Gamma (full width at half-maximum) and the value of 5.7 +- 1.4 x 10^-7 for the product of the Raman cross section rSERS and the surface concentration Ns of the benzenethiol SAM. The xxxx component of the resonant part of the third-order nonlinear optical susceptibility |3X (3)R/xxxx| for the 1574 cm^-1 SERS mode has been determined to be 4.3 +- 1.1 x 10^-5 cm g^-1 s^2. The SERS enhancement factor for the 1574 cm^-1 mode was determined to be 3.6 +- 0.9 x 10^7 using the value of 1.8 x 10^15 molecules/cm^2 for Ns.
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Summary

The surface-enhanced coherent anti-Stokes Raman scattering (SECARS) from a self-assembled monolayer (SAM) of benzenethiol on a silver-coated surface-enhanced Raman scattering (SERS) substrate has been measured for the 1574 cm^-1 SERS mode. A value of 9.6 +- 1.7 x 10^-14 W was determined for the resonant component of the SECARS signal...

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High efficiency coherent beam combining of semiconductor optical amplifiers

Published in:
Opt. Lett., Vol. 37, No. 23, 1 December 2012, pp. 5006-5008.

Summary

We demonstrate 40 W coherently combined output power in a single diffraction-limited beam from a one-dimensional 47-element array of angled-facet slab-coupled optical waveguide amplifiers at 1064 nm. The output from each emitter was collimated and overlapped onto a diffractive optical element combiner using a common transform lens. Phase locking was achieved via active feedback on each amplifier's drive current to maximize the power in the combined beam. The combining efficiency at all current levels was nearly constant at 87%.
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Summary

We demonstrate 40 W coherently combined output power in a single diffraction-limited beam from a one-dimensional 47-element array of angled-facet slab-coupled optical waveguide amplifiers at 1064 nm. The output from each emitter was collimated and overlapped onto a diffractive optical element combiner using a common transform lens. Phase locking was...

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Measurement of the third-order nonlinear optical susceptibility chi^(3) for the 1002-cm^-1 mode of benzenethiol using coherent anti-Stokes Raman scattering with continuous-wave diode lasers

Published in:
J. Raman Spectrosc., Vol. 43, No. 7, July 2012, pp. 911-916.

Summary

The components of the third-order nonlinear optical susceptibility x^(3) for the 1002-cm^?1 mode of neat benzenethiol have been measured using coherent anti-Stokes Raman scattering with continuous-wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of 2.8±0.3 X 10^-12, 2.0±0.2 X 10^-12, and 0.8±0.1 X 10^-12 cmg^-1 s^2 were measured for the xxxx, xxyy, and xyyx components of |3x^(3)|, respectively. We have calculated these quantities using a microscopic model, reproducing the same qualitative trend. The Raman cross-section sigma RS for the 1002-cm^-1 mode of neat benzenethiol has been determined to be 3.1±0.6 X 10^-29 cm^2 per molecule. The polarization of the anti-Stokes Raman scattering was found to be parallel to that of the pump laser, which implies negligible depolarization. The Raman linewidth (full-width at half-maximum) Gamma was determined to be 2.4±0.3 cm^-1 using normal Stokes Raman scattering. The measured values of sigma RS and Gamma yield a value of 2.1±0.4 X 10^-12 cmg^-1 s^2 for the resonant component of 3x^(3). A value of 1.9±0.9 X 10^-12 cmg^-1 s^2 has been deduced for the nonresonant component of 3x^(3).
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Summary

The components of the third-order nonlinear optical susceptibility x^(3) for the 1002-cm^?1 mode of neat benzenethiol have been measured using coherent anti-Stokes Raman scattering with continuous-wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of 2.8±0.3 X 10^-12, 2.0±0.2 X 10^-12, and 0.8±0.1 X 10^-12 cmg^-1...

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Sub-picosecond pulses at 100 W average power from a Yb:YLF chirped-pulse amplification system

Published in:
Opt. Lett., Vol. 37, No. 13, 1 July 2012, pp. 2700-2702.

Summary

We present a high-repetition-frequency, diode-pumped, and chirped-pulse amplification system operating at 106 W average output with excellent beam quality (M^2 = 1.3), based on cryogenically cooled Yb:YLF. 1 nJ seed pulses, derived from a mode-locked Ti:sapphire laser, are first amplified to 1 mJ pulse energy at 10 kHz repetition frequency in a regenerative amplifier. The second-stage, multipass amplifier increases the pulse energy to 10.6 mJ, resulting in a spectral width of 2.2 nm. The pulses are compressed to 865 fs in duration, which is 1.26 times the transform limit.
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Summary

We present a high-repetition-frequency, diode-pumped, and chirped-pulse amplification system operating at 106 W average output with excellent beam quality (M^2 = 1.3), based on cryogenically cooled Yb:YLF. 1 nJ seed pulses, derived from a mode-locked Ti:sapphire laser, are first amplified to 1 mJ pulse energy at 10 kHz repetition frequency...

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Rational design and optimization of plasmonic nanoarrays for surface enhanced infrared spectroscopy

Published in:
Opt. Express, Vol. 20, No. 11, 21 May 2012, pp. 11953-11966.

Summary

We present an approach for rational design and optimization of plasmonic arrays for ultrasensitive surface enhanced infrared absorption (SEIRA) spectroscopy of specific protein analytes. Motivated by our previous work that demonstrated sub-attomole detection of surface-bound silk fibroin [Proc. Natl. Acad. Sci. U.S.A. 106, 19227 (2009)], we introduce here a general framework that allows for the numerical optimization of metamaterial sensor designs in order to maximize the absorbance signal. A critical feature of our method is the explicit compensation for the perturbative effects of the analyte's refractive index which alters the resonance frequency and line-shape of the metamaterial response, thereby leading to spectral distortion in SEIRA signatures. As an example, we leverage our method to optimize the geometry of periodic arrays of plasmonic nanoparticles on both Si and CaF2 substrates. The optimal geometries result in a three-order of magnitude absorbance enhancement compared to an unstructured Au layer, with the CaF2 substrate offering an additional factor of three enhancement in absorbance over a traditional Si substrate. The latter improvement arises from increase of near-field intensity over the Au nanobar surface for the lower index substrate. Finally, we perform sensitivity analysis for our optimized arrays to predict the effects of fabrication imperfections. We find that
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Summary

We present an approach for rational design and optimization of plasmonic arrays for ultrasensitive surface enhanced infrared absorption (SEIRA) spectroscopy of specific protein analytes. Motivated by our previous work that demonstrated sub-attomole detection of surface-bound silk fibroin [Proc. Natl. Acad. Sci. U.S.A. 106, 19227 (2009)], we introduce here a general...

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External cavity beam combining of 21 semiconductor lasers using SPGD

Published in:
Appl. Opt., Vol. 51, No. 11, 10 April 2012, pp. 1724-1728.

Summary

Active coherent beam combining of laser oscillators is an attractive way to achieve high output power in a diffraction limited beam. Here we describe an active beam combining system used to coherently combine 21 semiconductor laser elements with an 81% beam combining efficiency in an external cavity configuration compared with an upper limit of 90% efficiency in the particular configuration of the experiment. Our beam combining system utilizes a stochastic parallel gradient descent (SPGD) algorithm for active phase control. This work demonstrates that active beam combining is not subject to the scaling limits imposed on passive-phasing systems.
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Summary

Active coherent beam combining of laser oscillators is an attractive way to achieve high output power in a diffraction limited beam. Here we describe an active beam combining system used to coherently combine 21 semiconductor laser elements with an 81% beam combining efficiency in an external cavity configuration compared with...

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Diffractive beam combining of a 2.5-kW fiber laser array

Published in:
ASSP 2012, Advanced Solid-State Photonics, 29 January - 1 February 2012.

Summary

Five 500-W fiber amplifiers were coherently combined with 79% efficiency using a diffractive optical element (DOE) combiner, generating a single beam whose M^2 = 1.1 beam quality exceeded that of the inputs.
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Summary

Five 500-W fiber amplifiers were coherently combined with 79% efficiency using a diffractive optical element (DOE) combiner, generating a single beam whose M^2 = 1.1 beam quality exceeded that of the inputs.

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