Study of Phase Matching Schemes in PPLN for THz Generation
In this paper we have studied the phase matching geometries of the slant—striped PPLN and the PPLN with grating vector normal to the input wave-vectors. In both of these PPLNs, the grating parameters (grating period and grating angle) are designed such that the THz is emitted from the surface of the PPLN thereby, reducing the loss of THz power due to absorption in lithium niobate. It was found that while keeping one of the input wavelength fixed at 1064 nm and tuning another wavelength from 1,070 to 1,080 nm we could obtain the THz wavelength tunable from 189.7 to 71.8 μm which corresponds to 1.58–4.17 THz frequency. In case of slant stripe PPLN, the grating period and grating angle required for generating this range of THz frequency, varies from 33.27 to 9.15 μm and 22.83°–16. 37. For PPLN with novel QPM, the required periods for the same range of THz frequency, varied from 39.8 to 10 μm. Study of effect of ±1 % systematic error in grating parameters on THz emission angle was also performed. It was found that error in grating parameters led to the deviation in THz emission angle in order to satisfy the phase matching condition. It was also found that in case of simultaneous occurrence of errors in grating parameters, the effect of errors was summed up when it occurred in opposite direction while, when errors were introduced in same direction the total effect (i. e. deviation in emission angle) was the difference of effect due individual error. However, the deviation in THz emission angle was very small and therefore, does not affect the THz extraction technique.
KeywordsTerahertz generation PPLN Grating parameters
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Authors would like to thank Director, IRDE for giving permission to publish this work.
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