Diffraction properties of volume hologram gratings illuminated by an ultrashort pulsed-laser beam

When a volume hologram grating is illuminated with a femtosecond laser pulse, its diffraction is crucial for practical application. In this paper, an analytical expression is given to calculate the diffractive spectrum of a transmission volume hologram grating illuminated by an ultrashort laser pulse. Numerical simulation shows that it is possible to achieve a large enough diffraction bandwidth of volume hologram grating in frequency domain for the bandwidth of 50-fs pulse for frequency-domain femtosecond pulse processing when the modulation index is properly selected. Furthermore, we predict that the diffractive spectrum can be controlled by tuning the modulation index of the volume hologram grating. Especially, the diffractive spectrum of the central wavelength is totally suppressed for some specific modulation index. Finally, we study the influence of loss on the diffraction efficiency of the volume hologram gratings. We found that, except decreasing the diffraction efficiency intensity, the presence of loss has little influence on the diffraction pattern. These novel results suggest that, by carefully designing the volume hologram gratings, it has great potential for the processing of the femtosecond pulses in the Fourier domain. An advantage of this present scheme is the flexibility and possibility of using the volume hologram grating to implement dynamic processing, with a potentially higher efficiency than by use of holographic thin films.