Stable CW low noise operation of a diode-pumped monolithic laser at 355 nm beyond 30 mW

Abstract

Low noise CW UV lasers are needed for applications in bioinstrumentation (cell sorting, cytometry…) and semiconductors (wafer inspection, micromachining …). We have recently demonstrated that such laser sources can be obtained with diode pumped solid state (DPSS) architectures. One key to success was the quasimonolithic structure of the laser. The advantages of quasi-monolithic DPSS lasers for UV generation are simplicity of design, compactness, efficiency and thus low power requirements and limited heating. In this paper, we present for the first time a long term characterization of the diode pumped CW 355 nm laser. The interplay between pump absorption, cavity length, 1064 mode size, walk-off angle, acceptance angle has been optimized. In our experiments, the temperature of each element of the laser was controlled and UV power, noise and spectra were monitored versus these temperatures. At 2.5 …