How to Shape Light with Spatial Light Modulators

The shaping of light fields, a topic of interest to the optics community for some time, has taken many forms, e.g., from coherent field mapping to diffusing elements for incoherent light shaping. Since the advent of the laser, structuring laser light in amplitude and phase has been achieved outside the laser cavity (with refractive, adaptive, and diffractive elements) and inside the laser cavity (through a variety of amplitude or phase objects that force the laser internally to oscillate on particular transverse modes). We will not discuss in detail the contribution of these tools for controlling light, but the reader is referred to the references provided for further details. Instead, we will consider a modern derivative of the above, namely shaping light with computer-generated holograms (digital holograms) using spatial light modulators (SLMs). Digital holography for structured light has enabled many new advances, ranging from classical to quantum physics, including communication, microscopy, imaging, metrology, and education. The advent of liquid crystal on silicon (LCoS) SLMs has made the aforementioned techniques accessible to the inexperienced researcher. LCoS devices, colloquially referred to as SLMs, have allowed researchers to display computer-generated holograms as images; thus, controlling light digitally can be realized with just a little know-how. Here, we will show how to “get started” with SLMs for the creation and detection of structured light fields. This guide focuses on the shaping of coherent light with these tools. We outline the means by which one can get started with digital holography as well as introduce phase-only, amplitude-only, and complex amplitude modulation as tools to create structured light fields in the laboratory.