Properties of 20-Hz eye-safe cascade Raman laser with Ba(NO3)2 crystal

Recently, lasers operating in the eye-safe wavelength around 1.5 μm have found increasing demand in the laser radar (LIDAR). Raman laser pumped by well established lasers such as Nd:YAG lasers is a favorable candidate with such characteristics at high repetition rate, narrow linewidth, and good beam quality.1 As the Raman conversion medium, a Ba(NO3)2 crystal has attracted much attention because of its high gain and strong mechanical properties.2 Laser output in the eye-safe wavelength region can be obtained with the Ba(NO3)2 crystal either in a first Stokes line pumped by 1.3 μm Nd:YAG laser2, or in a third Stokes line pumped by 1.06 μm Nd:YAG laser3. When the Raman crystal exhibits substantial residual absorption in the pump or Stokes wavelength, these solid-state Raman lasers require some thermal management to scale up to high average power systems such as in LIDAR. Hence, we experimentally studied the thermal characteristics of the Ba(NO3)2 cascade Raman conversion process.