A multilens Raman cell as a tool to obtain high optical quality and efficient 1st Stokes backward conversion

A multilens high pressure H2 cell has been used to demonstrate that efficient, high optical quality and low threshold down-conversion to 1st Stokes can be obtained also with a poor quality broadband pump, with just the condition that the pump pulsewidth is larger than the cell transit time. A backward 1st Stokes with 0.7 overall quantum efficiency conversion has been obtained from a broadband Nd:YAG duplicated laser.