Injecting pupil binary intensity map into the laboratory adaptive optics bench using phase-only LCoS-SLM device

Laboratory Adaptive Optics (AO) benches are the backbone of experimental testing and verification of new AO designs and architectures. These testbeds are particularly important when exploring unknown factors in the development of new instruments and facilities like future extremely large telescope AO systems. One of the key elements for simulating the performance of such systems in a smaller scale laboratory environment is the ability of projecting the precise intensity mask on the pupil plane. This mask often has binary (black or transparent/reflective) patterns that mimic the secondary obscuration and spider design of the telescope. Precise implementation of such intensity masks on the bench is important since studying effects such as “island/petaling effect” are critically dependent on the correct down-scaling and precise representation of the spider structure. Using a physical mask for such an application is very difficult since manufacturing and installing such fine structure pieces are difficult and hard to use. It is also necessary to build a new physical mask for each telescope system or scale that is desired for the experiment. In this paper, we introduce two methods of using a phase only Liquid Crystal on Silicon Spatial Light Modulator (LCoS-SLM) device as an alternative option to precisely and relatively easily inject the custom intensity mask into an optical bench. By implementing these methods on the LOOPS bench AO facilities of the LAM, we demonstrated that the contrast produced by both methods could be better than 2% (dark/bright ratio), which is sufficient for representing pupil obscuration in the majority of applications. We also show that by using one of these methods, it is possible to inject phase and binary intensity mask simultaneously which could greatly increase the versatility and ease of use of an experimental AO setup.