Friday, October 14, 2016

Seminar: "Highly nonlinear crystals for efficient mid-IR frequency conversion" by Peter G. Schunemann, 10.24.16/11:00AM-12:00PM/CREOL 103

Seminar: "Highly nonlinear crystals for efficient mid-IR frequency conversion" by Peter G. Schunemann
Monday, October 24, 2016 11:00 AM to 12:00 PM
CREOL Room 103

Peter G. SchunemannBAE Systems, Inc.

Advances in growth of the birefringent crystals ZnGeP2 and CdSiP2, as well as all-epitaxial processing of orientation-patterned semiconductors GaAs (OP-GaAs) and GaP (OP-GaP), are extending solid-state laser output deep into the mid-infrared. These materials exhibit the highest nonlinear coefficients and broadest infrared transparency ranges among all practical nonlinear optical crystals. In this review paper we describe the attractive properties of these materials, along with the unique capabilities and novel crystal growth and processing that continue to provide record-breaking conversion efficiencies and output powers in the mid-infrared.

Peter G. Schunemann has been a leading researcher in nonlinear optical materials for the last 30 years, authoring or co-authoring over 300 publications and 6 patents in the field. He is best known for developing the NLO chalcopyrite semiconductor ZnGeP2 (ZGP) for 2-micron-pumped mid-IR optical parametric oscillators (OPOs) for defense applications, primarily infrared countermeasures (IRCM). He was the first to grow large, crack-free, ZGP single crystals with sufficient quality for devices. He patented horizontal gradient freeze (HGF) growth in high-temperature transparent furnaces, and applied novel defect compensation and processing to achieve > 10-fold improvements in absorption loss, laser damage threshold, and 3-5-µm output power (world record–classified). He scaled his R&D process for production of ZGP crystals fielded in hundreds of IRCM laser systems mounted on military aircraft, successfully protecting against simultaneous multi-missile attacks.He has since demonstrated transparent HGF growth of exotic ternary and multinary compounds (AgGa1-xInxSe2, AgGaGeS4, AgGaTe2, HgGa2S4, CdGa2S4, CdGa2Se4, CaGa2S4, SrGa2S4, CaGa2Se4, GaSe) and applied understanding of defect chemistry to dramatically reduce optical losses in two other NLO chalcopyrites: CdGeAs2 (the highest d-coefficient of any known inorganic compound) and AgGaSe2, resulting in record conversion efficiencies for frequency doubling CO2-lasers. Mr. Schunemann rcenetly patented a new NLO chalcopyrite, CdSiP2, with the highest NLO coefficient of any crystal transparent and phase-matchable at 1064 nm and 1550 nm. In addition to birefringent materials, he successfully transitioned all-epitaxial growth of orientation-patterned gallium arsenide (OP-GaAs) – the first practical quasi-phasematched (QPM) semiconductor - from Stanford/AFRL to industry. He established dedicated MBE systems with auxiliary chambers for QPM template growth, and constructed a $3M Hydride Vapor Phase Epitaxy (HVPE) growth facility. He scaled OP-GaAs to 3” wafers with thicknesses up to 3.5 mm, reduced absorption losses by 4X, demonstrated multi-watt mid-IR output, the first cw OP-GaAs OPO, and the first cw OPO in any material pumped at a wavelength > 1.55 µm. External collaborations have achieved efficient THz output and femtosecond mid-IR frequency combs using OP-GaAs. This technology has recently been extended to orientation-patterned gallium phosphide (OP-GaP), an OP-GaAs analog that can be pumped at 1 µm or 1.55 µm with transparency out to 12 µm for next-generation LWIR devices. Numerous fs frequency converters in the 412 µm range have been demonstrated based on OP-GaP.

For more information:
Dr. Kenneth Schepler

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