Integrated Optical Switching Based on the Protein Bacteriorhodopsin†

Abstract

According to our earlier pioneering study, a dry film containing native bacteriorhodopsin (bR) shows unique nonlinear optical properties (refractive index change, controllable by light of different colors, greater than 2 x 10(-3)) that are in many respects superior to those of the materials presently applied in integrated optics. Here, we report on the first integrated optical application based on a miniature Mach-Zehnder interferometer (see Figs. 1 and 2) demonstrating a real switching effect by bR (efficiency higher than 90%) due to the M-state. Our results also imply that the refractive index change of the K-state (9 x 10(-4)) is high enough for fast switching.

Integrated optical biosensor for rapid detection of bacteria

“…Using saturating light intensities (e.g., 100 mW/cm 2 at 532 nm), two full periods (4π phase shift) could be covered, that makes the bR film suitable for adjusting the operating point of the interferometer to the highest sensitivity (i.e., to the mean of the minimum and maximum output values) [3]. As we have shown it earlier [4], under such conditions, the refractive index change of the bacteriorhodopsin film is ca. 5·10 −3 .…”

“…The Mach-Zehnder interferometer (MZI) was prepared by photopolymerization of NOA81 optical adhesive (Norland Products Inc., USA) by a so called direct laser writing technique that we used already for the preparation of micromachines and integrated optical structures [4,7]. Briefly, a microscope coverslip was spincoated by the adhesive (2100 rpm, 120 s), and subsequently mounted on the motorized X-Y stage (Märzhäuser) of an inverted microscope (Zeiss Axiovert 200) for writing.…”

Integrated optical application of bacteriorhodopsin

“…The above results have shown that an effective all-optical switching can be realized even with the fraction of the refractive index change mentioned before [62]. Recently, efficient integrated optical switching with a speed of a few microseconds, based on the M intermediate, has been experimentally demonstrated also at one of the telecommunication wavelengths (1550 nm) [63,64].…”

“…Consequently, if a probe laser beam at a wavelength outside of the excitation range of bR is coupled into an integrated optical device (e.g. a slab waveguide or a Mach-Zehnder interferometer) covered by an adlayer prepared of bR, the intensity of the output can be modulated by exciting the sample [61,62]. Optical switching and logical operations based on the BR→M transition were also shown later by other integrated optical structures, as well [63,67,68].…”

A bakteriorodopszin fehérje nemlineáris optikai tulajdonságainak hasznosítása integrált optikai alkalmazásokban

“…A logikai kapu működése a bR gerjesztésével megvalósítható fénymoduláción alapul [101], amely során közel 90 %-os kimeneti intenzitásváltozás érhető el [102]. A fénymoduláció alapja, hogy a bakteriorodopszin rétegben megvilágítás hatására eltolódik az alap-és intermedier állapotok aránya, ami -a fehérje szerkezetét és fotociklusát bemutató 3.2.1. fejezetben leírtak alapján -törésmutató-változást eredményez.…”