Preparation Of Bacteriorhodopsin Assembly Film And Research On Its Optical Nonlinearpies

Bacteriorhodopsin is an intensely-purple-colored protein molecules with its molecular weight of 26 kD and consists of a single polypeptide chain containing 248 amino-acids and retinal aldeyde chromophore. Bacteriorhodopsion has been the hot spot in the field of membrane protein research, since it was found in the late 1960's.It has not only the profound significance in the research of basic theory,but also the broad applied prospects.The photoelectric response and photo-induced allochroic effect of the bacteriorhodopsin film has already been found and some of them have already been used. But the nonlinear optical properties of Bacteriorhodopsin film are still necessary to be researched.In this article, manufacture of bR molecular assembly film and its optical nonlinearities are described. The self-assembly film with chemical deposit method and the bacteriorhodopsin Langmuir-Blodgett film of thirty-eight layers and 200nm were prepared. The UV absorb spetrum and Raman spectrum of the LB film that we prepared were measured. The result shows that the structure of the bacteriorhodopsin is not broken after Langmuir-Blodgett multilayer film being formed so the LB film of Bacteriorhodopsin has its potential application in the photoelectronics.The third order nonlinear optical properties of the bacteriorhodopsin Langmuir-Blodgett multilayer film were investigated with Z-scan technique. The film's third-order nonlinear susceptibility χ³ was measured at the wavelength of 400nm and 800nm. It is 2.5 × 10^-9 esu at 800nm and 1.1 × 10^-8esu at 400nm, respectively. It shows that the bacteriorhodopsin Langmuir-Blodgett multilayer film has high third-order nonlinear optical properties just as the bacteriorhodopsin. It also shows that Bacteriorhodopsin Langmuir-Blodgett film can be used in a lot of nonlinear photo-electronic device in the future.The degenerate four-wave mixing (DFWM) experiment of bR's self-assembly film and the second harmonic generation (SHG) of bR's LB film were also investigated, but the 3^rd and 2^nd order nonlinear susceptibilities were not obtained, respectively, because of the low bR concentration and weak optical signal. The result is still unknown that Langmuir-Blodgett multilayer film has its high 3^rd order nonlinear susceptibility but low 2nd order nonlinear susceptibility.