Electrical and optical properties of CdGeAs2 single crystals irradiated with fast electrons

Abstract

The effects of 10 MeV fast electron irradiation on conductivity type, resistivity, and optical absorption of CdGeAs2 single crystals were studied. Irradiation of as-grown p-type crystals with a fluence of 1×1017 cm−2 caused compensation of the semiconductor and a marked improvement in the optical transmission. A level of absorption below 0.1 cm−1 at 5⩽λ⩽11 μm was registered. Increase in the fluence to 2×1017 cm−2 led to conversion to n-type, a drop in the resistivity and deterioration of the transmission. Analysis of the absorption in p-type crystals showed that transitions from the V2 and V3 split-off bands to the V1 valence band represent the major absorption mechanism. Splitting energies ΔE2−1=0.15 eV and ΔE3−1=0.35 eV have been calculated. Absorption in n-type crystals increased as λ2.4 indicating absorption by free electrons and their scattering by optical phonons. The effect of irradiation on the optical absorption of CdGeAs2 is assigned to the radiation-induced changes in the compensation level.

Optical stochastic cooling for RHIC using optical parametric amplification

“…Absorption is expected to fall as techniques for preparing crystals improve [16]. For example, it can be decreased dramatically by exposing the crystal to low energy electrons to introduce lattice defects that trap the free carriers primarily responsible for the high absorption [17]. In addition, by using several shorter crystals and introducing a new pump beam into every segment, we can compensate for the loss of pump energy from the remaining absorption.…”

Development of CO 2 waveguide lasers and laser technology for remote sensing

“…We propose to expand coverage by employing nonlinear crystal technology to generate efficient tunable infrared beams by difference frequency generation (DFG). The approach has only recently become more feasible with reports 14 of improvements in the transmission and power-handling capabilities of the infrared nonlinear crystal cadmium germanium arsenide (CGA). CGA has an extremely high figure of merit, but absorptions in the 4-12 mm wavelength range exceeding 0.4 cm -1 have restricted its use to low power applications.…”

Optical parametric generation in CGA crystal

“…Lately, it became possible, owing to the advancements in the crystal growth and after-growth processing, to produce large size CGA crystals with improved transmission [1][2][3]. As a result, highly efficient frequency doubling of CO 2 laser radiation (conversion efficiency 28% at room temperature and 50% at 77 K) [1] and difference frequency generation (at room temperature) with photon conversion efficiency >20% in the 7-20 lm spectral range [3] have been reported in CGA.…”

“…In this paper, we report the first demonstration of optical parametric generation (OPG) in CGA (which we regard as a logical step to achieving an OPO in this crystal), as well as efficient SHG operation. The CGA crystal was grown at Inrad, by the horizontal gradient freeze technique, and was subjected to post-growth treatment (irradiation and annealing) [2] to decrease its room temperature optical absorption. The 6 Â 8 mm 2 cross-section, 7 mm long sample designed for type I phase matching was cut at h ¼ 33°and u ¼ 0°.…”

“…It transmits light between 2.4 and 18 lm and is a perfect candidate for second-harmonic generation (SHG) and nonlinear-optical frequency conversion via optical parametric oscillation (OPO), specifically into the second atmospheric window (8-12 lm). In the past, the linear absorption of as-grown CGA crystals was high ($1 cm À1 ) which precluded its wide use in nonlinear optics.Lately, it became possible, owing to the advancements in the crystal growth and after-growth processing, to produce large size CGA crystals with improved transmission [1][2][3]. As a result, highly efficient frequency doubling of CO 2 laser radiation (conversion efficiency 28% at room temperature and 50% at 77 K) [1] and difference frequency generation (at room temperature) with photon conversion efficiency >20% in the 7-20 lm spectral range [3] have been reported in CGA.…”