Fig. 1. Working principle and phase match conditions of 45° TFG

Fig. 2. Numerical simulation results of PER of 45° TFG. (a) PER as a function of refractive modulation of 30 mm grating; (b) PER as a function of grating length for different δn

Fig. 3. 45° TFG multi-pass inscription analysis results. (a) PER measurement results varying with continuous inscribing time; (b) diagram of grating misalignment between inscriptions; (c) PER modulation coefficient as a function of misalignment for different photosensitivity correction coefficient η for secondary inscription

Fig. 4. PER as a function of polarization state of incident UV light. (a) Coherent contrast for different polarization states; (b) PER measurement results of 10 mm TFG inscribed under different polarization states of incident UV light

Fig. 5. Self-feedback enhanced 45° TFG inscription. (a) Diagram of inscription system; (b) feedback flow chart; (c) self-feedback inscription results

Fig. 6. Performance test results of 45° TFG. (a) PER and insertion loss of 10 TFG samples before and after annealing; (b) relationship between polarization-dependent loss and wavelength