Dual-wavelength diode lasers for background-free Raman spectroscopic measurements

Shifted excitation Raman difference spectroscopy (SERDS) enables the separation of weak Raman signals from intense background disturbances such as sample fluorescence and ambient light. It requires dual-wavelength excitation for subsequent measurements. Using grating-stabilized diode lasers, the required functionalities can be specifically designed and implemented at chip level. In this work, tailor-made dual-wavelength distributed Bragg reflector (DBR) ridge waveguide diode lasers emitting around 785 nm will be discussed. The devices provide optical output powers in the 100- mW range and alternating wavelength operation at switching frequencies up to 100 Hz. Heater elements next to the DBR gratings enable adjusting the spectral distance within a 2 nm range in 50 ms. Master oscillator power amplifier configurations help to enter Watt-class level optical output powers. Selected Raman and SERDS experiments will demonstrate the capabilities of these devices for spectroscopic applications.