Harmonics and subharmonics of a grating in Bi12SiO20

The formation of gratings in photorefractive materials has been widely investigated over two decades for applications in non-linear optics, optical signal processing, optical storage and dynamic holography. Bismuth silicon oxide, Bi₁₂SiO₂₀, with its high sensitivity and fast response, has emerged as a very promising material for real-time applications. It is shown that when two frequently detuned pump beams of equal intensity are incident on a BSO crystal, output beams corresponding to higher harmonics and subharmonics of the fundamental grating are produced. It is suggested that in order to explain theoretically all of the observed effects, the higher Fourier terms in the solution of Kukhtarev´s equations (1979) must be retained, gratings due to higher harmonic beams must be included and, for the case of the subharmonics, the new amplification mechanism must be used