Laser generation and amplification of TE and TM modes in a semiconductor optical GaAs waveguide with distributed feedback generated by a space charge wave

Abstract

We propose a scheme for generating and amplifying coupled optical TE and TM waves in the mid-IR range provided by a grating formed by a space charge wave in a planar waveguide based on GaAs and GaAlAs semiconductors. An undamped harmonic space charge wave with the frequency Ω=ωm−ωn (where ωm and ωn are the frequencies of the forward and backward optical eigenwaves) can be formed in a longitudinal constant electric field in the predomain mode. The coupling coefficients for the optical TE and TM modes of the perturbed n-GaAs waveguide have been obtained. For pairs of the TE and TM modes of the same indices (m = n), the reflectance and transmittance dependences on the carrier concentration and pump level have been found. Generation of the forward and backward waves at a wavelength of 10.6 μm is shown for TE0 and TM2 modes at the gain factor of γ ≈ 152 cm−1 and 155 cm−1, respectively. The obtained results can be used to create semiconductor two-frequency coherently synchronized oscillators based on space charge wave–optical mode interaction.