High power LD-end-pumped Nd: YVO4 laser as a pump source for Raman fiber laser

摘要

A LD-single-end-pumped Nd:YVO_4 CW all-solid-state laser with maximum output power 12.5W at 1064nm was designed to pump the cascaded phosphosilicate fiber Raman laser. The Nd:YVO_4 laser is lower in cost than Yb-doped cladding fiber laser which is usually used as a pump for Raman fiber laser. However, it is inefficient to couple pump beam into single mode fiber (SMF). The coupling efficiency from pump beam to SMF is largely affected by the beam quality. Thus, a high coupling efficiency requires maintaining laser's operation in the TEM_(00) mode while scaling the power. The beam quality and maximum output power of the Nd:YVO_4 laser is restricted by the thermal lens and fracture within the gain medium under high pump intensity conditions. The thermal effects was decreased by using a 3×3×10mm~3 Nd:YVO_4 crystal with a low neodymium-doped concentration (0.3at%). Furthermore, a plane-plane resonant cavity with large mode volume and a large pump size was also used to reduce the effects. The Nd:YVO_4 laser with maximum output power 12.5W and M~2 < 1.2 was obtained. More power than 4W was injected into cascaded Raman cavity at the maximum pump power and about 1W coherent second-order Stokes radiation at 1484nm was achieved.