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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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High-power, low-noise 1.5-um slab-coupled optical waveguide (SCOW) emitters: physics, devices, and applications

Summary

We review the development of a new class of high-power, edge-emitting, semiconductor optical gain medium based on the slab-coupled optical waveguide (SCOW) concept. We restrict the scope to InP-based devices incorporating either InGaAsP or InGaAlAs quantum-well active regions and operating in the 1.5-μm-wavelength region. Key properties of the SCOW gain medium include large transverse optical mode dimensions (>;5 × 5 μm), ultralow optical confinement factor (Γ ~ 0.25-1%), and small internal loss coefficient (α i ~ 0.5 cm-1). These properties have enabled the realization of 1) packaged Watt-class semiconductor optical amplifiers (SOAs) having low-noise figure (4-5 dB), 2) monolithic passively mode-locked lasers generating 0.25-W average output power, 3) external-cavity fiber-ring actively mode-locked lasers exhibiting residual timing jitter of
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Summary

We review the development of a new class of high-power, edge-emitting, semiconductor optical gain medium based on the slab-coupled optical waveguide (SCOW) concept. We restrict the scope to InP-based devices incorporating either InGaAsP or InGaAlAs quantum-well active regions and operating in the 1.5-μm-wavelength region. Key properties of the SCOW gain...

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Noncontact optical detection of explosive particles via photodissociation followed by laser-induced fluorescence

Published in:
Opt. Express, Vol. 19, No. 19, 12 September 2011, pp. 18671-18677.

Summary

High-sensitivity (ng/cm2) optical detection of the explosive 2,4,6- trinitrotoluene (TNT) is demonstrated using photodissociation followed by laser-induced fluorescence (PD-LIF). Detection occurs rapidly, within 6 laser pulses (~7 ns each) at a range of 15 cm. Dropcasting is used to create calibrated samples covering a wide range of TNT concentrations; and a correspondence between fractional area covered by TNT and PD-LIF signal strength is observed. Dropcast data are compared to that of an actual fingerprint. These results demonstrate that PD-LIF could be a viable means of rapidly and remotely scanning surfaces for trace explosive residues.
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Summary

High-sensitivity (ng/cm2) optical detection of the explosive 2,4,6- trinitrotoluene (TNT) is demonstrated using photodissociation followed by laser-induced fluorescence (PD-LIF). Detection occurs rapidly, within 6 laser pulses (~7 ns each) at a range of 15 cm. Dropcasting is used to create calibrated samples covering a wide range of TNT concentrations; and...

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Coherent combining of a 4 kW, eight-element fiber amplifier array

Published in:
Opt. Lett., vol. 36, No. 14, 15 July 2011, pp. 2686-2688.

Summary

Commercial 0:5kW Yb-doped fiber amplifiers have been characterized and found to be suitable for coherent beam combining. Eight such fiber amplifiers have been coherently combined in a tiled-aperture configuration with 78% combining efficiency and total output power of 4kW. The power-in-the-bucket vertical beam quality of the combined output is 1.25 times diffraction limited at full power. The beam-combining performance is independent of output power.
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Summary

Commercial 0:5kW Yb-doped fiber amplifiers have been characterized and found to be suitable for coherent beam combining. Eight such fiber amplifiers have been coherently combined in a tiled-aperture configuration with 78% combining efficiency and total output power of 4kW. The power-in-the-bucket vertical beam quality of the combined output is 1.25...

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Packaged, high-power, narrow-linewidth slab-coupled optical waveguide external cavity laser (SCOWECL)

Published in:
IEEE Photonics Technol. Lett., Vol. 23, No. 14, 15 July 2011.
Topic:

Summary

We report the demonstration of an InGaAlAs/InP quantum-well, high-power, low-noise packaged semiconductor external cavity laser (ECL) operating at 1550 nm. The laser comprises a double-pass, curved-channel slab-coupled optical waveguide amplifier (SCOWA) coupled to a narrow-bandwidth (2.5 GHz) fiber Bragg grating passive cavity using a lensedfiber. At a bias current of 4 A, the ECL produces 370 mW of fiber-coupled output power with a Voigt lineshape having Gaussian and Lorentzian linewidths of 35 kHz and 1 kHz, respectively, and relative intensity noise < -160 dB/Hz from 200 kHz to 10 GHz.
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Summary

We report the demonstration of an InGaAlAs/InP quantum-well, high-power, low-noise packaged semiconductor external cavity laser (ECL) operating at 1550 nm. The laser comprises a double-pass, curved-channel slab-coupled optical waveguide amplifier (SCOWA) coupled to a narrow-bandwidth (2.5 GHz) fiber Bragg grating passive cavity using a lensedfiber. At a bias current of...

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Cryogenic Yb3+ -doped materials for pulsed solid-state laser applications

Published in:
Opt. Mat. Expr., Vol. 1, No. 3, 1 July 2011, pp. 434-450.

Summary

We review recent progress in pulsed lasers using cryogenically-cooled Yb3+ -doped gain media, with an emphasis on high average power. Recent measurements of thermo-optic properties for various host material at both room and cryogenic temperature are presented, including themral conductivity, coefficient of thermal expansion and refractive index. Host materials reviewed include Y2O3, Lu2O3, Sc2O3, YLF, YSO, GSAG, and YVO4. We report on performance of several cryogenic Yb lasers operating at 5-kHz pulse repetition frequency (PRF) a Q-switched Yb:YAG laser is shwon to operate at 114-W average power, with 16-ns pulse duration. A chirped pulse amplifier achieves 115-W output using a composite Yb:YAG/Yb:GSAG amplifier, with pulses that compress to 1.6 ps. Finally, a high-average-power femtosecond laser based on Yb:YLF is discussed, with results for a 10-W regenerative amplifier at 10-kHZ PRF.
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Summary

We review recent progress in pulsed lasers using cryogenically-cooled Yb3+ -doped gain media, with an emphasis on high average power. Recent measurements of thermo-optic properties for various host material at both room and cryogenic temperature are presented, including themral conductivity, coefficient of thermal expansion and refractive index. Host materials reviewed...

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Angle-and polarization-dependent collective excitation of plasmonic nanoarrays for surface enhanced infrared spectroscopy

Summary

Our recent work has showed that diffractively coupled nanoplasmonic arrays for Fourier transform infrared (FTIR) microspectroscopy can enhance the Amide I protein vibrational stretch by up to 105 times as compared to plain substrates. In this work we consider computationally the impact of a microscope objective illumination cone on array performance. We derive an approach for computing angular- and spatially-averaged reflectance for various numerical aperture (NA) objectives. We then use this approach to show that arrays that are perfectly optimized for normal incidence undergo significant response degradation even at modest NAs, whereas arrays that are slightly detuned from the perfect grating condition at normal incidence irradiation exhibit only a slight drop in performance when analyzed with a microscope objective. Our simulation results are in good agreement with microscope measurements of experimentally optimized periodic nanoplasmonic arrays.
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Summary

Our recent work has showed that diffractively coupled nanoplasmonic arrays for Fourier transform infrared (FTIR) microspectroscopy can enhance the Amide I protein vibrational stretch by up to 105 times as compared to plain substrates. In this work we consider computationally the impact of a microscope objective illumination cone on array...

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Uni-traveling-carrier variable confinement waveguide photodiodes

Summary

Uni-traveling-carrier waveguide photodiodes (PDs) with a variable optical confinement mode size transformer are demonstrated. The optical mode is large at the input for minimal front-end saturation and the mode transforms as the light propagates so that the absorption profile is optimized for both high-power and high-speed performance. Two differently designed PDs are presented. PD A demonstrates a 3-dB bandwidth of 12.6 GHz, and saturation currents of 40 mA at 1 GHz and 34 mA at 10 GHz. PD B demonstrates a 3-dB bandwidth of 2.5 GHz, a saturation current greater than 100 mA at 1 GHz, a peak RF output power of + 19 dBm, and a third-order output intercept point of 29.1 dBm at a photocurrent of 60 mA.
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Summary

Uni-traveling-carrier waveguide photodiodes (PDs) with a variable optical confinement mode size transformer are demonstrated. The optical mode is large at the input for minimal front-end saturation and the mode transforms as the light propagates so that the absorption profile is optimized for both high-power and high-speed performance. Two differently designed...

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Thermally tuned dual 20-channel ring resonator filter bank in SOI (silicon-on-insulator)

Published in:
CLEO 2011, Conf. on Lasers and Electro-Optics, 1 May 2011.

Summary

Two 20-channel second-order optical filter banks have been fabricated. With tuning, the requirements for a wavelength multiplexed photonic AD-converter (insertion loss 1-3 dB, extinction >30 dB and optical bandwidth 22-27 GHz) are met.
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Summary

Two 20-channel second-order optical filter banks have been fabricated. With tuning, the requirements for a wavelength multiplexed photonic AD-converter (insertion loss 1-3 dB, extinction >30 dB and optical bandwidth 22-27 GHz) are met.

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Microwave photonic applications of slab-coupled optical waveguide devices

Published in:
2010 23rd Annual Mtg. of the IEEE Photonics Society, 10 November 2010, pp. 479-480.
Topic:

Summary

The semiconductor slab-coupled optical waveguide (SCOW) concept is a versatile device platform that has enabled new classes of high-power, low-noise single-frequency lasers, mode-locked lasers, optical amplifiers, and photodiodes for analog optical links and photonic analog-to-digital converters.
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Summary

The semiconductor slab-coupled optical waveguide (SCOW) concept is a versatile device platform that has enabled new classes of high-power, low-noise single-frequency lasers, mode-locked lasers, optical amplifiers, and photodiodes for analog optical links and photonic analog-to-digital converters.

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