Low power spatial light modulator with pharaonis phoborhodopsin

Spatial light modulation (SLM) has been theoretically analysed in pharaonis phoborhodopsin (ppR) and its mutants based on nonlinear intensity induced excited-state absorption, to achieve large percentage modulation at low power. Amplitude modulation of probe laser read beam (Ip′) transmissions at 560, 512 and 390 nm, corresponding to the peak absorption of ppRO, ppRKL and ppRM intermediate states, respectively, of ppR photocycle, by write beam intensity (Im′) at 498 nm, corresponding to the peak absorption of the initial ppR state, have been analysed using the rate equation approach, considering all six intermediate states in its photocycle. The SLM characteristics are shown to be sensitive to the normalized small signal absorption coefficient (β) and the rate constants of intermediates. For a given Im′ range, there is an optimum value of β (βopt) for maximum percentage modulation. We can achieve 100% modulation of the read beam if the initial ppR state does not absorb the respective probe beams. The SLM characteristics of F86D ppR have also been used to design an all-optical XOR logic gate. High dynamic range and sensitivity can be achieved at low write beam intensities in ppR compared to wild-type bacteriorhodopsin (WT-bR).