Pulse recording of dynamic holograms in bismuth silicate crystal in a broad wavelength range

Abstract

The formation of dynamic holograms in a photorefractive bismuth silicate crystal by nanosecond laser pulses with a change in the radiation wavelength is studied. An original scheme for recording holograms is proposed to preserve the grating period when operating at different wavelengths. The method of pulsed recording of dynamic gratings based on the proposed optical scheme is applied, which ensures the fulfillment of the Bragg condition for probing radiation. The originality of the scheme lies in the use of the first orders of diffraction of a transmitting diffraction grating as the reference and signal waves, as well as a telescopic system used to fix the period of the recorded grating, regardless of the wavelength used. Kinetic dependences of the diffraction efficiency of dynamic holograms in a photorefractive bismuth silicate crystal are obtained with a change in the wavelength of recording radiation in the actual spectral range (from 450 nm to 600 nm). The effect of the manifestation of competing recording mechanisms of short-lived (hundreds of microseconds) and long-lived (seconds) gratings, the contribution of which depends on the wavelength of the radiation recording the hologram, has been established. The optimal wavelength for obtaining the highest diffraction efficiency of holograms is determined. It is shown that radiation in the blue-green region of the spectrum leads to the predominant recording of a short-lived grating, while long-lived gratings dominate in the red region of the spectrum. The need to study photorefractive crystals of the sillenite family is determined by their use for multiplex recording of dynamic holograms and the implementation of the adaptive interferometry method to track changes in objects in real time.

Keywords

• dynamic holograms
• photorefractive crystals
• bismuth silicate
• pulse holography
• diffraction efficiency
• wavelength tuning