LiF, an underestimated supercontinuum source in femtosecond transient absorption spectroscopy

Abstract

We present supercontinua generated in LiF and CaF(2) revealing that LiF is advantageous especially in the near UV region since it pushes the cut-off wavelength about 17 nm towards lower wavelengths and the occurrence of color centers, which has been considered as a drawback up to now, is not a limitation for its applicability in femtosecond transient absorption spectroscopy. Even though the color centers occur within a short time of illumination, they do not influence the supercontinuum generation significantly and they can furthermore, if desired, be eliminated from the substrate simply by heating. Thus LiF is a promising substrate for broad band measurements in the UV/vis range.

Ultrafast supercontinuum generation in bulk condensed media

“…Although neglected in some studies 148 , formation of persistent color centers in LiF was generally considered as a major drawback to its application for SC generation. However, a more recent study revealed that color centers only slightly modify the ultraviolet cut-off (at 270 nm) of the SC spectrum on the long-term (several hours) operation 191 .…”

LiSAF: an efficient and durable nonlinear material for supercontinuum generation in the ultraviolet

“…However, the nonlinear materials that produce the largest spectral blue shifts, LiF and CaF 2 , exhibit several drawbacks that are unattractive for practical applications. More specifically, LiF is prone to rapid formation of colour centres, which modify the SC spectrum to a certain degree [19,20]. On the other hand, optical damage in CaF 2 due to heat accumulation develops very quickly even at relatively low (1 kHz) pulse repetition rate, so the crystal should be continuously translated [21].…”