Abstract

In the earlier work¹ the three-photon resonance at cyclotron frequency Ω_c, in semiconductors pumped by two lasers with their frequency difference close to Ω_c, has been predicted and observed. Here we consider the feasibility of hysteretic excitation of such a resonance in narrow-gap semiconductors which is based on the nonparabolicity of the narrow-gap semiconductor conduction band. The expected effect is analogous to three-photon hysteretic resonance of free cyclotron electrons in vacuum.² However, this quasi-relativistic nonlinearity caused by nonparabolicity in semiconductors is much larger than that caused by free relativistic electrons, since the nonlinearity in semiconductors is scaled to the gap energy E_g, which is much smaller than rest energy of free electron m₀c². We consider an example where two different lines 10.6 and 9.4 µm of a CO₂ laser used as driving radiations, with the cyclotron three-photon excitation expected at λ_c ≃ 83.03 µm. Assuming the momentum relaxation time to be of the order of 10⁻¹¹ s, we estimate the critical intensity required to obtain a hysteretic frequency difference cyclotron excitation to be 3.4 × 10⁴ W/cm² for InSb; 2.2 × 10⁵ W/cm² for HgTe; 2.2 × 10⁶ W/cm² for GaAs.

© 1986 Optical Society of America