Diffraction characteristics of volume holographic gratings with finite size for the ultrashort pulsed beam readout

Abstract

Using the two-dimensional coupled-wave theory, the diffraction characteristics of volume holographic gratings (VHGs) with finite size planar are studied for the ultrashort pulsed beam (UPB) readout. Numerical simulations are show for the special case of the overlapping VHGs reconstructed by a Gaussian-shaped UPB in temporal domain. The effects of the material dispersion and the finite size of the grating on the intensity distributions of the diffracted and transmitted pulsed beams, and the total diffraction efficiency are given. Our study also shows the differences between the diffraction characteristics of the finite size planar VHG for the UPB readout and those for the CW readout. And, comparison of the diffraction characteristics between the finite size VHGs and the one dimensional VHGs under the UPB readout is given. 1． IntroductionVolume holographic gratings (VHGs) have been widely used in many fields, such as information storage, processing, and display, and for optoelectronic devices such as waveguides and filters [1][2][3] , because of its characteristics of high diffraction efficiency, wavelength selectivity, and angular selectivity. Recently, the remarkable progress of the technique to generate ultrashort pulsed beams (UPBs) has extended the bandwidth of optical communications and signal processing.With which, VHGs have attracted increasingly more attention in manipulating the laser output pulses to achieve functional waveforms with large bandwidths which can be utilized in a variety of applications because of their flexibility and the possibility of using them to implement dynamic processing [4][5][6][7][8][9] . Based on the coupled wave theory of Kogelnik [10] , Y. Ding [8] et al. have shown both theoretically and experimentally that in the frequency domain it is possible to achieve an enough large diffraction bandwidth of the one dimensional(1-D) VHG for the bandwidth of 100-fs pulses. Further, the study of Teng [9] has included the dispersion effect in the crystal.However, there is no doubt that in some of the applications of VHGs only two dimensions are of interest, where the size of the VHGs in the two dimensional (2-D) plane in which the grating vector lies is restricted. Moreover, the two beams involved in grating recording or reconstruction may access two orthogonal surfaces (typically called the 90 geometry [11] ). Although many researchers have analyzed the diffraction characteristics of the finite size planar holographic gratings under continuous wave (CW) readout [12][13][14][15][16] , for the case that the finite size VHG is illuminated by a UPB, and the grating material dispersion is been considered, few studies have touched upon as we knew. Actually, the

Influence of grating shapes on diffraction properties of ultrashort pulse beam by local volume holographic grating

“…Volume holographic gratings (VHGs) for manipulating laser output pulses to achieve functional waveforms with large bandwidths can be utilized for a variety of applications, for example, pulse shaping devices, etc [10][11]. The diffraction properties of VHGs with some simple characteristic grating boundary read by an ultrashort pulse beam have been studied [12][13], which are different from the diffraction properties of the continuous wave [15][16][17], the distributions of the transmitted and diffraction pulsed beams are greatly influenced by the grating geometrical size, the pulse width of the input UPB, and the dispersion effect of the grating materials. But little work has been performed on ultrashort pulsed beams propagating through a volume holographic grating with arbitrary boundary, the spatial and temporal feature of UPBs simultaneously should be affected greatly by the grating boundaries, which would be directly related to the device performance and efficiency.…”