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
CREOL Room 103
Celebrating the International Year of Light 2015
Peter G. Schunemann
BAE Systems, Inc
Abstract
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.
Biography
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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