Intensity Dependent Nonlinear Absorption in Direct and Indirect Band Gap Crystals under Nano and Picosecond Z-Scan

Dimple Sharma, Poonam Gaur, Bharam Pal Malik, Nageshwar Singh, Arun Gaur

Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology (D.C.R.U.S.T), Murthal, Sonipat, India.
Department of Physics, Hindu P.G. College, Sonipat, India.
Laser Systems Engineering Division (L.S.E.D.), Raja Rammanna Centre for Advanced Technology (CAT), Indore, India.

DOI: 10.4236/opj.2012.22013                

Abstract

The nonlinear absorption properties of direct (GaN) and indirect (CdI2) band gap crystals have been studied by using an open aperture Z-scan technique under fundamental (1064 nm) and frequency doubled (532 nm) wavelength respectively with 10 ns or 60 ps pulse durations. Direct band gap crystal exhibits two and three photon absorption at all input irradiances. On the other hand, at low input irradiance the indirect band gap crystal exhibits saturable absorption (SA). At higher input irradiances two and three photon absorption becomes dominant. A monotonic increase of the nonlinear absorption coefficients with increasing laser pulse duration from 60 ps to 10 ns is observed for GaN and CdI2 crystals.

Keywords

Direct and Indirect Band Gap Crystals; Two Photon Absorption; Three Photon Absorption; Saturated Absorption

Conflicts of Interest

The authors declare no conflicts of interest.

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