Monolithic Dual-Wavelength DBR Diode Laser at 633 nm Suitable for Raman Spectroscopy in Fluorescent Environments

Raman spectroscopy is a well-established analytical tool that provides a molecular fingerprint of the sample [1]. Utilization of diode lasers as a light source had a big impact in this field, especially for the realization of portable Raman sensors. However, weak Raman signals can be masked by the background interferences. Among others, an effective technique to address this issue is shifted excitation Raman difference spectroscopy (SERDS). It requires a narrowband light source with two slightly shifted emission wavelengths. Corresponding dual-wavelength Y-branch distributed Bragg reflector (DBR) diode lasers suitable for SERDS have been demonstrated and applied in the near-infrared spectral range [2]. At lower excitation wavelengths for higher Raman intensities, the realization of such light sources in the red spectral range around 633 nm has yet been difficult due to the material system and technological challenges. In this paper, for the first time, a monolithic dual-wavelength Y-branch DBR diode laser emitting at 633 nm suitable for Raman spectroscopy and SERDS is presented.