Manufacture Of Transmission Volume Phase Holographic Grating With High Diffraction Efficiency In A Wide Waveband

Volume phase holographic grating (VPHG) has the characteristics of high diffractionefficiency, low noise, high resolution and is widely used in the fields of wavelengthdivision multiplexing, head up display, astronomical spectroscopy, etc. With the rapiddevelopment of space remote sensing in recent years, the detection system should be met ahigher request. A novel imaging spectrometer with a cemented prism-grating-prism (PGP)spectral component fuses optical images and spectroscopy and turns to be a research hotspot for its advantages of high spectral resolution and small volume. As a result, theresearch of transmission VPHG used in PGP component has great significance.The diffraction properties of transmission VPHG which is applied in VIS/NIRwaveband are investigated theoretically and experimentally in this paper. Firstly, rigorouscoupled wave analysis (RCWA) and kogelnik’s coupled wave theory are introduced briefly.Based on RCWA and the software named G-Solver, a single grating with the frequency of196lp/mm is designed and optimized. In order to improve the grating diffraction efficiency,a composite structure formed by two gratings that their frequency difference equals to196lp/mm is proposed in this paper. The two gratings with the frequency around1000lp/mm are designed and optimized based on Kogelnik’s coupled wave theory and thefrequency of900lp/mm and704lp/mm is defined at last. Theoretical analysis andcalculating results show that the composite grating can improve both the peak diffractionefficiency and the average diffraction efficiency among the required waveband.Then, the transmission VPHG recorded in dichromated gelatin (DCG) is manufactured. Testing system is established for the measurement and analysis of thediffraction efficiency and angular selectivity of the transmission VPHG. From the results, itcan be seen that by adjusting and controlling the preparation conditions of DCG plates, theexposure level and post-processing technique of the grating, the performances of thetransmission VPHG approximate to the design requirements can be obtained. Using acomposite structure formed by two high frequency gratings, the diffraction efficiency boththe peak one and the average one among the required waveband are improved greatly. Thiscan get a low frequency grating with high diffraction efficiency and support the furtherdevelopment of PGP imaging spectrometer.