Synchronously-pumped all-solid-state Raman lasers based on YVO4 and GdVO4 crystals with pulse shortening by higher than 30 times down to 850 fs

Abstract

New possibilities to use the zircon-type YVO4 and GdVO4 Raman-active crystals for extreme SRS-radiation pulse shortening higher than 30 times down to the inverse value of the vibrational Raman line width in a synchronouslypumped crystalline Raman laser with combined long (ν1) and short (ν2) shift Raman conversion have been found. It is caused by strong broadening of the short-shift bending vibration ν2 line in the spontaneous Raman spectrum of these crystals. We report characteristics of all-solid-state extracavity Raman lasers based on the 16-mm long a-cut YVO4 (ν1 = 889 cm–1, ν2 = 376 cm–1) and GdVO4 (ν1 = 882 cm–1, ν2 = 382 cm–1) crystals under synchronous pumping by a 1063-nm 35-picosecond Nd:GdVO4 laser. Lasing was obtained in the YVO4 (GdVO4) Raman laser at not only the ν1- shifted first Stokes wavelength of 1173 nm (1174 nm), but also at the (ν1 + ν2)-shifted Stokes wavelength of 1228 nm (1228 nm) with slope efficiency of 5.8 % (5.0 %) and output pulse energy up to 11 nJ (10 nJ) at 1228 nm. At 50 μm positive detuning of the external cavity length the strongest 30-fold and 42-fold shortening of the (ν1+ν2)-shifted Raman radiation pulse down to 1.2 ps and 850 fs in the YVO4 and GdVO4 crystals, respectively, has been achieved. These values are close to the inverse values of the ν2 line widths of 11 cm–1 and 24 cm–1, respectively.