Design of H-PDLC grating array chopper applied in frequency division multiplexed integrated confocal microscopy

Abstract

A new type of electrically controlled optical chopper based on Holographic Polymer Dispersed Liquid Crystal (HPDLC) grating array is demonstrated in this paper. H-PDLC grating can be erased and become transparent to the incident beam when applied the external voltage. H-PDLC grating recovers and diffracts incident light in the original way after removal the driving voltage. Thus the intensity and the frequency modulation to the incident beam can be achieved through adjusting the voltage applied on the H-PDLC cell. Compared with a conventional chopper, the H-PDLC gratings exhibit more advantage like much faster response time, the grating array is much more integrated and easier to be fabricated etc. Moreover, electro-optical properties including response time and diffraction efficiency of H-PDLC gratings are investigated. By optimizing some parameters, H-PDLC chopper cell with a microsecond response time and high diffraction efficiency is obtained. The driving voltage of H-PDLC can be reduced through controlling the droplet size in H-PDLC and the thickness of the grating. As the application example, the chopper is applied in the new born frequency division multiplexed multichannel fluorescence confocal microscopy so that it can improve the temporal and spatial resolution ability of the microscopy system.