Dual-wavelength composite grating semiconductor laser for Raman detection

Dual-wavelength lasers are utilized in dual-wavelength interferometric absorption measurement, difference frequency terahertz generation, and shifted excitation Raman difference spectroscopy. Consequently, dual-wavelength lasers with narrow linewidths and stable wavelengths have become a focal point of research. This paper presents the design of a monolithically integrated dual-wavelength composite grating laser, which integrates laterally coupled gratings and ridge surface gratings with different periods. To reduce mode competition and enhance stability, we designed an isolation groove structure between the two Bragg systems of the laser to achieve selection of two longitudinal modes. At an operating current of 0.28A, two wavelengths with a separation of 0.75 nm were obtained, with central wavelengths of 782.47 nm and 783.22 nm, respectively. When the operating current was in the range of 0.28A to 0.35A, the laser achieved stable dual-wavelength oscillation, with a maximum dual-wavelength output power of 71.95 mW. Thus, the dual-wavelength devices developed in this work can be applied to shifted excitation Raman difference spectroscopy.