Comparison of individual and common wavelength-operation for 785 nm Y-branch DBR ridge waveguide diode lasers with adjustable spectral distance

Abstract

An experimental comparison between individual and common wavelength-operation of a Y-branch distributed Bragg reflector (DBR) ridge waveguide (RW) laser at 785 nm with an electrically adjustable spectral distance is presented. The dual-wavelength Y-branch laser combines two laser cavities via a Y-section to a common output section. DBR gratings with different grating periods are associated with the two cavities, which set the emission wavelengths of the two branches. Implemented resistive heater elements allow separate wavelength tuning of the two branches, which can be operated individually for alternating emission wavelengths in applications such as differential absorption spectroscopy or shifted excitation Raman difference spectroscopy. Common wavelength operation simultaneously generates two emission lines suitable for the generation of THz radiation using difference frequency mixing. Hereby, the devices could potentially be used as single-chip light sources for a combination of Raman and THz applications. For the wavelength-operation comparison presented, the devices were operated up to optical output powers of about 105 and 185 mW in individual and common wavelength-operation mode, respectively. In individual operation mode, the devices show spectral single-mode emission over the whole operation range. In common operation mode, the spectral emission is predominantly single mode up to an optical output power of 65 mW. In both operation modes, mode hops typical for DBR lasers occur. At an optical output power of 50 mW, tuning of the spectral distance between the two wavelengths using the implemented resistor heaters is demonstrated. In both modes of wavelength operation, a flexible frequency difference between 0 and 0.8 THz (0 and 1.6 nm) with predominantly single-mode spectral emission is obtained.