Integrated 795nm narrow linewidth MOPA butterfly laser for quantum sensing and magnetometry

High-power narrow-linewidth laser sources in the near-infrared are essential for many applications spanning Raman spectroscopy, quantum, and biomedical fields. The wavelength 760–795 nm range is widely used in medical diagnostics, such as detecting cancer biomarkers and analyzing blood flow. Of particular interest are narrow-linewidth lasers delivering watt-level output power at 780 nm and 795 nm, resonant with the D2 and D1 absorption lines, respectively, as well as 785 nm, a widely used wavelength in Raman spectroscopy due to its favorable trade-off between Raman scattering efficiency and background fluorescence. Tapered amplifiers (TAs) combined with narrow linewidth distributed Bragg reflector (DBR) seeds are well suited for these applications, providing high output power and excellent beam quality, while remaining compatible with compact butterfly packaging. In this work, we present a 795 nm master-oscillator power-amplifier (MOPA) fully packaged in a butterfly module. The narrow linewidth of the DBR seed is achieved using surface gratings fabricated by electron beam lithography (EBL) and inductively coupled plasma (ICP) etching. The DBR seed exhibits a linewidth < 500 kHz with output power exceeding 200 mW, which is subsequently amplified by the TA chip to the watt-class power without sacrificing the spectral characteristics of the seed laser. The DBR and TA are integrated into separate 14-pin butterfly packages with fiber-coupled DBR module output feeding the TA module with free-space output or into one extended butterfly package housing both seed DBR and TA.