Monday, March 2, 2015

Seminar: "New Materials for Mid-Infrared Nonlinear Optics" by Peter G. Schunemann 3.6.15/12:00pm-1:00pm/ CREOL Rm 103

Seminar: "New Materials for Mid-Infrared Nonlinear Optics" by Peter G. Schunemann
Friday, March 6, 2015 12:00 PM to 1:00 PM
CREOL Room 103

Celebrating the International Year of Light 2015

Peter G. Schunemann
BAE Systems, Inc

Mid-infrared nonlinear optical crystals have matured in the last twenty-five years from scientific curiosities into practical robust materials generating efficient laser output in the 2-12 micron spectral range.  ZnGeP2 (ZGP) in particular has emerged as the NLO material of choice for frequency conversion between 2 and 8 microns, and is growing in importance with the advent of high power thulium fiber lasers. ZGP, however, still has two main limitations: 1) its transparency and phase-matching range make it incompatible with 1- and 1.5-micron laser pumping; and 2) its usefulness for generating output in the 8-12 micron atmospheric window is limited by severe multi-phonon absorption. These limitations have been overcome by several new mid-infrared nonlinear crystals: cadmium silicon phosphide (CdSiP2), orientation-patterned gallium arsenide (OP-GaAs), and orientation-patterned gallium phosphide (OP-GaP).
CdSiP2 (CSP) is a bulk birefringent chalcopyrite analog of ZGP grown by horizontal gradient freeze growth in a transparent furnace. Its larger band gap (512 nm) and birefringence (-0.05) allows for 1- and 1.5-mm pumping, and its nonlinear coefficient (d14=85 pm/V) and thermal conductivity (13 W/mK) are dramatically higher than existing materials (AgGaS2, AgGaSe2, and PPLN) that can be pumped at these wavelengths.
OP-GaAs and OP-GaP are quasi-phase-matched (QPM) nonlinear optical semiconductors grown by a novel all-epitaxial process.  First, polar-on-nonpolar MBE is used to produce a GaAs (GaP) film with an orientation that is inverted with respect to the substrate. The inverted layer is photo-lithographically patterned and etched with the desired grating structure, and both orientations are then re-grown by hydride vapor phase epitaxy (HVPE) at rates up to 200mm/hr to produce thick (> 1mm), low-loss (< 0.01cm-1) QPM layers for in-plane laser pumping. OP-GaAs has the highest gain among all QPM materials, and can be pumped at 2-mm to generate output at 8-12 mm and beyond, whereas OP-GaP is a low-loss QPM ZGP analog than can be pumped with 1-mm lasers.
Finally, all-epitaxial growth technology is being used to grow ternary semiconductors with engineered band gaps for use as optical limiters.
Recent advances in growth, processing, and NLO device performance of all these materials will be discussed. 

Peter G. Schunemann has been a leading researcher in nonlinear optical materials for the last 25 years, authoring or co-authoring over 250 publications in the field. He received B.S. and M.S. degrees in Materials Science and Engineering from MIT in 1984 and 1987 before joining BAE Systems, where he has led a series of development efforts to produce improved crystals for mid-infrared frequency conversion, most notably ZnGeP2, AgGaSe2, CdGeAs2, CdSiP2, and OPGaAs. His work on ZnGeP2 in particular, a critical component for next generation laser-based IRCM systems, earned him a Quarterly Technical Achievement Award in 1992, the Jack L. Bowers Award in 1994 (the company’s highest technical award), and a Nova Award in 1995 (Lockheed Martin’s highest honor for technical excellence), and the Association of Old Crows Technology Hall of Fame award in 2002.  He is an OSA Fellow, a member of SPIE and MRS, and is currently the president of AACG (American Association of Crystal Growth).

For additional information:

Dr. Konstantin L. Vodopyanov

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