Chinese Journal of Lasers, Volume. 36, Issue 3, 677(2009)
Fabrication of Linearly Chirped Phase Mask
The diffraction characteristics of the linearly chirped phase mask is investigated using rigorous coupled-wave theory. The results show that the groove depth and duty cycle of phase mask must be controlled within the range of 242~270 nm and 0.37~0.50 respectively, in order to make the zero order diffraction efficiency less than 2% and the ±1 order diffraction efficiency more than 35%. Based on the above analysis, a linearly chirped phase mask with the center period of 1000 nm, ruled area of 100 mm×10 mm and chirp rate of 1 nm/mm has been fabricated by a new technique, which combines holographic-ion beam etching and reactive ion beam etching. The experiment and simulation both indicate that the Ar ion beam etching can modify the initial photoresist grating profile and produce a suitable duty cycle under the CHF3 reactive ion beam etching. Experimental measurements show that the zero order diffraction efficiency is less than 2%, with the ±1 order diffraction efficiency more than 35% and the maximum nonlinear coefficient of 1.6%. Theoretical analysis also indicates that the phase masks can be used to fabricate the UV written chirped fiber Bragg gratings.
Get Citation
Copy Citation Text
Liu Quan, Wu Jianhong, Yang Weipeng, Fang Lingling. Fabrication of Linearly Chirped Phase Mask[J]. Chinese Journal of Lasers, 2009, 36(3): 677