Numerical and experimental study of an ultrabroadband modeless Ce:LiCAF ultraviolet laser: Multiwavelength dynamics and power amplification

Abstract

This study investigates the generation and power amplification of an ultrabroadband modeless Ce:LiCAF ultraviolet (UV) laser using combined numerical and experimental approaches. Pumped at 266 nm, the Ce:LiCAF source produces a modeless UV spectrum from 275 to 330 nm with a dominant peak at ≈288.5 nm (FWHM ≈16 nm) and a weaker band near 310 nm. We develop a multiwavelength propagation model in which the spectrum is represented by discrete wavelength channels with wavelength-dependent emission, absorption, and excited-state absorption cross-sections, and we include pump absorption, gain saturation, and amplified spontaneous emission (ASE). Experimentally, a four-pass Ce:LiCAF amplifier is implemented, and spectra and pulse energies are measured after the oscillator and after each pass at a fixed 266 nm pump energy. The amplified source delivers up to 1 mJ per pulse, with the FWHM of the 288.5 nm peak reduced from 16 nm to 7 nm, indicating moderate gain narrowing while preserving the two-band spectrum. Numerical predictions agree with the measurements (deviations <10 % in output energy and <1 nm in peak wavelength), showing that this modeless Ce:LiCAF system is a promising source for broadband UV absorption spectroscopy and trace-gas detection.