Two Photon Absorption, Nonlinear Refraction, And Optical Limiting In Semiconductors
Abstract
Twophoton absorption coefficients /32 of ten direct gap semiconductors with bandgap energy Eg varying between 1 .4 and 3.7 eV were measured using 1.06 µm and 0.53 um picosecond pulses. 2 was found to scale as E43, as predicted by theory for the samples measured. Extension of the empirical relationship between 2 and Eg to InSb with Eg = 0.2 eV also provides agreement between previously measured values and the predicted 02. In addition, the absolute values of $2 are in excellent agreement (the average difference being <26%) with recent theory, which includes the effects of nonparabolic bands. The nonlinear refraction induced in these materials was monitored and found to agree well with the assumption that the selfrefraction originates from the twophotongenerated free carriers. The observed selfdefocusing yields an effective nonlinear index as much as two orders of magnitude larger than CS2 for comparable irradiances. This selfdefocusing, in conjunction with twophoton absorption, was used to construct a simple, effective optical limiter that has high transmission at low input irradiance and low transmission at high input irradiance. The device is the optical analog of a Zener diode.
 Publication:

Optical Engineering
 Pub Date:
 August 1985
 DOI:
 10.1117/12.7973538
 Bibcode:
 1985OptEn..24..613V