Coupled distributed feedback laser system at 820 nm for THz beat-frequency generation

We present a coupled distributed feedback (DFB) laser system, based on AlGaAs/GaAs epitaxially grown compound semiconductor, with electroluminescence near 820 nm. This DFB laser system supports two lateral modes sharing a Bragg grating, thereby enabling simultaneous lasing operation at two different frequencies. We recorded a dual-mode operation with a 4.2 nm wavelength spacing, corresponding to a 1.86 THz beat frequency, and an output power of 14.7 mW at an injection current of 195 mA. Compared to previous works on dual-mode DFB lasers, this design simplifies the fabrication process, potentially enables tunability of the beat frequency, and offers greater compatibility with low temperature grown GaAs (LT-GaAs) high-frequency photodetectors.