Optically pumped GaAs-Ga1−xAlxAs half-ring laser fabricated by liquid-phase epitaxy over chemically etched channels

Abstract

Half‐ring waveguides (5 μm width, 185 μm radius) fabricated by liquid‐phase expitaxial growth of Ga_1−xAl_xAs and GaAs layers over preferentially etched channels in GaAs substrates were made to lase by optical pumping with a N₂ laser (λ=3371 Å) at 77 °K. The half‐ring lasers had a threshold of about 2×10⁴ W/cm²; a bending loss per radian α_c−1; strong TE polarization; and a well‐defined circumferential mode structure: Δλ≃1.07 Å at λ=8280 Å for a 580‐μm‐long cavity. Straight guides of similar profile to the circular guides were made to lase for comparison. A calculated 0.5‐Å mode broadening due to transient heating during the pump laser pulse accounts for the observed lasing spectra.