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30 to 50 ns liquid-crystal optical switches

Published in:
Optics Express, Vol. 18, No. 18, 30 August 2010, pp. 1886-18893.

Summary

The optical switching time of twisted-nematic liquid-crystal cells using the liquid crystals, 5CB (C,H,,-Ph-Ph-CN), 50CB(C,Hw O-Ph-Ph-CN) and PCH5 (C,H,,-Cy-Ph-CN) have been characterized as a function of temperature, prebias voltage and switching voltage, V. The transition time from 90 % to 10 % transmission scales as V-1.9 and is limited to 30 to 50 ns by the liquid-crystal breakdown electric field, - 100 V I'm-I The time fi-om the initial switching voltage step to 90 % transmission, delay time, decreases with increasing prebias and switching voltage. For 5CB and 50CS the delay time approaches a constant value at higher electric fields, >10 V ~1Il,-1. Both the transition and delay times decrease with increasing temperature. The minimum transition time at temperatures a few degrees below the nematicisotropic temperature are 32, 32, and 44 ns and delay times are 44, 25 and 8 ns for 5CB, 50CB, and PCH5 respectively.
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Summary

The optical switching time of twisted-nematic liquid-crystal cells using the liquid crystals, 5CB (C,H,,-Ph-Ph-CN), 50CB(C,Hw O-Ph-Ph-CN) and PCH5 (C,H,,-Cy-Ph-CN) have been characterized as a function of temperature, prebias voltage and switching voltage, V. The transition time from 90 % to 10 % transmission scales as V-1.9 and is limited to...

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High-power, slab-coupled optical waveguide laser array packaging for beam combining

Published in:
SPIE Vol. 6478, Photonics Packaging, Integration, and Interconnects VII, 23-25 January 2007, pp. 647806-1 - 647806-12.

Summary

Linear arrays of slab coupled optical waveguide lasers (SCOWL) are ideal sources for beam combining of array elements using techniques such as wavelength beam combining (WBC) and possibly coherent beam combining (CBC). SCOWL array elements have very high brightness, low divergence nearly diffraction limited output beams. Arrays of up to 1.2 cm in width containing as many as 240 elements have been demonstrated. In this presentation, the packaging techniques developed to ensure proper performance of SCOWL arrays will be described, with particular emphasis on the application to beam combining. A commercial high performance micro impingement cooler (MIC) was used to provide thermal management for these arrays. Based on performance data for this cooler, a numerical thermal model was constructed and used to investigate the thermal performance for several packaging schemes. In order to promote uniform optical performance of SCOWL array elements, assembly procedures, which included fluxless soldering using In and AuSn solder alloys, along with the use of thermal expansion matching materials were investigated. These techniques resulted in minimal contraction ([approx] 2 um) and smile ([approx]1 um) of the laser bar during the packaging procedure. Precise control of these parameters is required in order to minimize any detrimental impact on the resultant WBC beam quality. CBC of SCOWL arrays requires phase control of the array elements. Array packaging providing for individual electrical addressability of the array elements has been developed and demonstrated, allowing for phase control by current adjustment.
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Summary

Linear arrays of slab coupled optical waveguide lasers (SCOWL) are ideal sources for beam combining of array elements using techniques such as wavelength beam combining (WBC) and possibly coherent beam combining (CBC). SCOWL array elements have very high brightness, low divergence nearly diffraction limited output beams. Arrays of up to...

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Spectral beam combining of a broad-stripe diode laser array in an external cavity

Published in:
Opt. Lett., Vol. 25, No. 6, 15 March 2000, pp. 405-407.

Summary

The outputs from an 11-element, linear diode laser array with broad stripes have been beam combined into a single beam with a beam quality of ~20X diffraction limited in the plane of the junction. This beam combining was achieved by use of a common external cavity containing a grating, which simultaneously forces each array element to operate at a different, but controlled, wavelength and forces the beams from all the elements to overlap and propagate in the same direction. The power in the combined beam was 50% of the output from the bare laser array.
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Summary

The outputs from an 11-element, linear diode laser array with broad stripes have been beam combined into a single beam with a beam quality of ~20X diffraction limited in the plane of the junction. This beam combining was achieved by use of a common external cavity containing a grating, which...

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