Dual-wavelength composite grating semiconductor laser for Raman detection

•The dual-wavelengthsemiconductor laser with composite grating discussed in this paper is fabricated using UV lithography, offering significant cost advantages.•The device described in this paper achieves longitudinal mode selection for two wavelengths through the design of ridge surface gratings with different periods, lateral coupled gratings, and isolation grooves.•The grating structures mentioned in this paper are all surface high-order gratings, which do not require secondary epitaxy and thus do not affect the epitaxial layer material.•The device described in this paper achieves stable dual-wavelength lasing within a driving current range of 0.28 A to 0.35 A, providing a novel approach for the development of portable Raman spectrometers. 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.