Digital micro-mirror devices for laser beam shaping

Structured laser beams have numerous applications, for example mode division multiplexing, optical tweezers and even astronomy. Spatial Light Modulators are typically used to display digital holograms, however they have a low refresh rate, only work with a single polarisation and operate on a limited range of wavelengths. Digital Micro-mirror Devices are able to spatially modify the amplitude of incident light as opposed the the phase and are increasing in popularity due to their high refresh rate, polarisation and wavelength invariance and they are able to work as digital holograms with the right encoding. We describe how these devices may be used in a laboratory environment for modal decomposition as well as some of their disadvantages. We describe a method to accurately measure the flatness of a DMD, which is one of the major issues with the devices.