Large-format Spatial Light Modulators for Shaping High Power Lasers

Laser plasma accelerators and associated light sources, including high brightness x-ray generation through Compton backscattering, offer the potential for transformative applications in science, industry, medicine, homeland security, and future particle colliders. The beam power and efficiency of such systems is limited by our ability to correct for phase imperfections during amplification. Liquid Crystal on Silicon (LCoS) Spatial light modulators (SLMs) have the millions of pixels of phase control and >100 Hz speeds required for phase correction, but are currently unable to handle the average powers, fluences, and beam diameters of current and next generation kW-class lasers. MLO already manufactures the largest and highest frame rate SLMs in the world. Building on this experience, we will build new large-area SLMs that can handle average powers at the few kW-level and energy densities of 250 mJ/cm2 for 30 fs pulses. Our strategy will use a combination of efficient active cooling, custom liquid crystal, improved construction, and increasing SLM size to reduce peak fluence and average power density. Phase I: We redesigned our 17 mm x 17 mm SLM for high-power applications, changing the heat dissipation path as well as nearly every material that makes up the SLM. We found that early versions of our design were already able to operate at 400 W average power, the highest laser power we had available in Phase I. Phase II: We will test our Phase I design at higher average powers, and project that it will likely be able to operate at 1 kW average power. We will concentrate additional material development on the components that our Phase I experiments revealed had the lowest damage thresholds. Once we have our final material design tested on the 17 x 17 mm SLM, we will transfer the design to our 30.7 x 30.7 mm SLM. The SLMs developed in this work will find a broader market in laser manufacturing, where SLMs can produce custom beam profiles that can improve the efficiency of laser-based additive manufacturing, laser welding, and laser marking for aerospace and medical applications. Long-range communications and defense applications are also target markets for this design, which can be adapted for wavelengths from visible to mid-wave IR.