All-optical light modulation in pharaonis phoborhodopsin and its application to parallel logic gates

作者：Sharma P^*; Roy S

来源：Journal of Applied Physics, 2004, 96(3): 1687-1695.

DOI：10.1063/1.1765856

All-optical light modulation in pharaonis phoborhodopsin (ppR) protein has been analyzed considering its ppR(O) state dynamics based on nonlinear intensity-induced excited-state absorption. Amplitude modulation of a cw probe laser beam transmission at 560 nm corresponding to the peak absorption of ppR(O) intermediate state through ppR, by a modulating cw pump laser beam at 498 nm corresponding to the peak absorption of initial ppR state has been analyzed considering all six intermediate states in its photocylce using the rate equation approach. The transmission characteristics have been shown to exhibit a dip at relatively lower pump intensity values compared to bacteriorhodopsin, which is sensitive to normalized small-signal absorption coefficient (beta), rate constants of ppR(M) and ppR(O) states, and absorption of the ppR(O) state at 498 nm. There is an optimum value of beta for a given pump intensity range for which maximum modulation can be achieved. It is shown that 100% modulation can be achieved if the initial state of ppR does not absorb the probe beam. The results have been used to design low power all optical parallel NOT, AND, OR, XNOR, and the universal NAND and NOR logic gates for two cases: (i) only changing the output threshold and (ii) considering a common threshold with different beta values. At typical parameters, wild-type (WT) ppR based logic gates can be realized at considerably lower pump powers than WT-bR.

• 出版日期2004-8-1