title: All-optical switching in Pharaonis phoborhodopsin protein molecules.
abstract: Low-power all-optical switching with pharaonis phoborhodopsin (ppR) protein is demonstrated based on nonlinear excited-state absorption at different wavelengths. A modulating pulsed 532-nm laser beam is shown to switch the transmission of a continuous-wave signal light beam at: 1) 390 nm; 2) 500 nm; 3) 560 nm; and 4) 600 nm, respectively. Simulations based on the rate equation approach considering all seven states in the ppR photocycle are in good agreement with experimental results. It is shown that the switching characteristics at 560 and 600 nm, respectively, can exhibit negative to positive switching. The switching characteristics at 500 nm can be inverted by increasing the signal beam intensity. The profile of switched signal beam is also sensitive to the modulating pulse frequency and signal beam intensity and wavelength. The switching characteristics are also shown to be sensitive to the lifetimes of ppR(M) and ppR(O) intermediates. The results show the applicability of ppR as a low-power wavelength tunable all-optical switch.
authors.affiliation: Department of Physics and Computer Science, Dayalbagh Educational Institute, Deemed University, Agra 282 005, India. sukhdevr@hotmail.com
authors.forename: Sukhdev
authors.initials: S
authors.lastname: Roy
authors.forename: Takashi
authors.initials: T
authors.lastname: Kikukawa
authors.forename: Parag
authors.initials: P
authors.lastname: Sharma
authors.forename: Naoki
authors.initials: N
authors.lastname: Kamo
mesh_terms: D003198:Computer Simulation; D039301:Computers, Molecular; D025602:Halorhodopsins / Q000737:chemistry* / Q000528:radiation effects*; D008027:Light; D008956:Models, Chemical; D008958:Models, Molecular; D019633:Natronobacterium / Q000737:chemistry* / Q000528:radiation effects; D010777:Photochemistry / Q000379:methods; D011829:Radiation Dosage; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000528:radiation effects*; D012815:Signal Processing, Computer-Assisted
chemical_list: D025602:Halorhodopsins; D025603:Sensory Rhodopsins; C061508:sensory rhodopsin II protein, archaeal