Comparison of acousto-optic and liquid crystal tunable filters for laser-induced breakdown spectroscopy

In this paper, we report the first time-resolved laser-induced plasma image s acquired using a liquid crystal tunable filter (LCTF). We also compare th e use of LCTFs and acousto-optic tunable filters (AOTFs) for time-resolved plasma imaging applications in terms of resolution, out-of-band rejection, and image quality. Application of tunable filter technologies to plasma ima ging is unlike other Spectroscopic imaging methods because of the intense a nd spectrally broad background generated by a laser-induced plasma. High qu ality images of the distribution of atomic emission within a laser-induced plasma can be achieved using both AOTFs and LCTFs. However, additional filt ers are needed for rejection of wavelengths outside the tuning ranges of th e devices. Both devices exhibited superior resolution in the lower working range of the filters (similar to 500 nm) with the LCTF exhibiting superior spectral resolution to the AOTF.