Abstract

There is great interest in the generation of shaped femtosecond pulses in this deep UV [1] in order to extend coherent control studies to this spectral range. Direct pulse shaping based on liquid crystal spatial light modulators (LC-SLM) or acousto-optic modulators [2] presents severe limitations when used in the deep UV spectral range. To circumvent this limitation, indirect pulse shaping techniques have been developed. In such approach, a desired pulse shape is transferred from a spectral region, where direct shaping techniques are applicable, to the spectral region of interest through the frequency mixing of the shaped pulse with a second pulse with a flat spectral phase. Moreover, it is interesting to combine this spectral phase transfer method with a broadband generation technique that can ultimately allow the generation of few cycle UV pulses. One of best way to achieve such ultra broadband phase-matching condition is using a four-wave mixing scheme in noble gas-filled hollow fibers [3], where pulses as short as 8 fs at 270 nm have been successfully generated. Such ultra-short deep UV pulses have great importance to study ultrafast dynamics in biologically system such as small molecules which usually undergo photochemical reactions upon deep UV (200 – 300 nm) irradiation [4]. In order to investigate this possibility we implemented four-wave mixing scheme based on the hollow core fiber phase-matching method for the generation of deep UV pulses combined with the spectral phase transfer technique. In this work, we report on spectral π-step phase transfer from near infrared to deep UV pulses by four-wave mixing in argon using the broadband phase-matched guided wave technique. Such step-phase transfer was revealed by observation of depletion on the UV spectrum

© 2015 IEEE