Dual‐wavelength monolithic Y‐branch distributed Bragg reflection diode laser at 671 nm suitable for shifted excitation Raman difference spectroscopy

A dual‐wavelength monolithic Y‐branch distributed Bragg reflection (DBR) diode laser at 671 nm is presented. The device is realized with deeply etched surface DBR gratings by one‐step epitaxy. A maximum optical output power of 110 mW is obtained in cw‐operation for each laser cavity. The emission wavelengths of the device are 670.5 nm and 671.0 nm with a spectral width of 13 pm (0.3 cm⁻¹) and a mean spectral distance of 0.46 nm (10.2 cm⁻¹) over the whole operating range. Together with a free running power stability of ± 1.1% this most compact diode laser is ideally suited as an excitation light source for portable shifted excitation Raman difference spectroscopy (SERDS).