Experiments of electrically controlled optical choppers based on H-PDLC gratings

An experimental investigation on a novel electrically controlled optical chopper based on holographic polymer dispersed liquid crystal (H-PDLC) gratings is presented in this paper. In order to realize the chopping function, a corresponding electrical driving source and controlling circuit are developed for the phase type H-PDLC grating, so that the H-PDLC chopper can not only modulate a light beam with variable frequencies at different duty ratios but also generate other types of waveform modulation such as the sinusoidal modulation to replace the traditional rectangular modulation. Experimental results on one-channel, two-channel and four-channel H-PDLC optical choppers showed that, in comparison with the mechanical chopper counterpart, this device had the advantages of (1) lower noise without mechanical moving part, (2) higher conveniences in terms of changing its operational frequencies, duty ratios and modulation curves, and (3) multi-channel modulation capability. Therefore, it will have a great potential for applications that requires frequency modulations such as frequency modulated confocal microscopy system.