Diffraction-Based Phase Calibration of Spatial Light Modulators With Binary Phase Fresnel Lenses

Abstract

Abstract-We propose a simple and robust method to determine the calibration function of phase-only spatial light modulators (SLMs). The proposed method is based on the codification of binary phase Fresnel lenses (BPFLs) onto an SLM. At the principal focal plane of a BPFL, the focal irradiance is collected with a single device just able to measure intensitydependent signals, e.g., CCD camera, photodiodes, power meter, etc. In accordance with the theoretical model, it is easy to extract the desired calibration function from the numerical processing of the experimental data. The lack of an interferometric optical arrangement, and the use of minimal optical components allow a fast alignment of the setup, which is in fact poorly dependent on environmental fluctuations. In addition, the effects of the zeroorder, commonly presented in the diffraction-based methods, are drastically reduced because measurements are carried out only in the vicinity of the focal points, where main light contributions are coming from diffracted light at the BPFL. Furthermore, owing to the simplicity of the method, full calibration can be done, in most practical situations, without moving the SLM from the original place for a given application.

Progress in Phase Calibration for Liquid Crystal Spatial Light Modulators

“…The simple one could only realize the global measurement. Self-referenced − 8 µm <20 Directly diffractive [27] Out-referenced 1-pixel 8 µm Several Twyman-Green [28,33] Diffraction pattern analyzed 8 × 8-pixel 14 µm <10 Directly diffractive [11] Optical elements generated Global 1 Directly diffractive [45] Polarization methods 1-pixel 11.5 µm Several Retro-reflection [46,47] 1 Images or data groups needed approximately for 512 × 512 pixels' calibration at one grayscale. 2 Basic alignments for the best spatial resolution.…”

“…A simple and robust method for determining the calibration function with binary phase Fresnel lenses is proposed [45]. As shown in Figure 8, a Fresnel lens is designed with binary phase level distribution: 1 φ and 2 φ .…”

High Precision Optical Wavefront Generation Using Liquid Crystal Spatial Light Modulator (LC-SLM)

“…The measurement of phase modulation characteristics of interferometry mainly depends on the displacement of fringe pattern, but the two beams have to travel a long path in the air before the interference, and the mechanical vibration, air turbulence, and other environmental factors will cause the change of their optical path difference, resulting in a large fluctuation in the acquisition of fringe pattern. Diffraction methods are mainly based on irradiance measurements of the diffraction pattern originated by phase holograms at their focal planes [18][19][20][21]. Intensity transmission can well suppress the influence of environmental vibration and air turbulence, but from the perspective of phase extraction, the operation process of phase estimation is more complex.…”

Cost-Efficient Hybrid WDM-MDM-Ro-FSO System for Broadband Services in Hospitals

“…Apart from wavelength [10], polarization [11] and time [12] multiplexing schemes, MDM enables multimode data transmission by multiplexing through a single optical channel. In MDM, modes can be excited through various mechanisms such as spatial light modulators [13], offset launch [14], high-speed VCSEL arrays [15] and photonic crystal fibers (PCF) [16]. Researchers have used four OAM beams (1 ±1 and 1 ±3) to transmit 400 Gbps data through an FSO link of 120 m in 2016 [17]; MDM-OFDM scheme to transmit 80 Gbps data through an FSO link of 50 km in 2017 [7]; and MDM-based polarisation phase shift key scheme to transmit 80 Gbps data through an FSO link of 90 km in 2020 [18].…”