Renewable plasma mirrors for repetition-rated, multi-PW lasers using ultrathin liquid crystal films

Plasma mirrors (PMs) can play a vital role in ultrashort pulse, high-power laser experiments and applications due to their ability to improve temporal pulse contrast and to redirect intense pulses. For low repetition rate, multi-PW laser systems (e.g., one shot per hour), conventional PMs may suffice, however, this is less likely to be the case for high repetition rate, multi-PW systems operating at a shot every few minutes or higher. We describe an approach using ultrathin (~20 nm) liquid crystal (LC) films that we believe can meet this need. The weak field reflectivity is low due to thin film interference (<1%) and LC films can be wiped at high repetition rate over long periods of time, depending on the diameter. We describe previous work on the use of such films for plasma mirrors and for tunable thickness targets. We also describe the physical processes determining plasma mirror effectiveness and the challenges of using PMs in multi-PW systems. Earlier work utilized the LC material 8CB in the smectic phase regime for LC PM’s.  In this work, we discuss the physics of LC film formation and overview ongoing efforts to use different LC’s and mixtures to tune the film properties.

This work was supported by the DOE Office of Science, Fusion Energy Sciences under Contract Nos. DE-SC0022092 and DE-SC0022094 and by the U.S. National Science Foundation under Cooperative Agreement No. (PHY-2329970).