Interaction of a two-color laser with aluminum nitride crystal leading to THz radiation

Generation of THz waves from interaction of a two-color laser with aluminum nitride crystal has been investigated theoretically. The focus of study has been directed towards exploring the potential of nonlinear optical difference frequency generation for emission in the THz spectrum. Leveraging Sellmeier's dispersion formula, an in-depth analysis of refractive index behavior was conducted. The analysis revealed the conditions for phase matching within the range of 0.5–12 THz for 1064 nm laser wavelength at room temperature. The maximum walk-off angle was verified 0.5°, suitable for co-linear wave interactions. The Manley–Row equations were applied, showcasing energy conversion efficiency in the order of \({10}^{-3}\) in an ideal lossless medium and \({10}^{-5}\) when accounting for losses. The quasi-phase matching (QPM) technique was utilized to enhance the quality of analysis and establishing an optimal periodicity wavelength. This adjustment facilitated tuning within the range 54–68 THz for 1064 nm by manipulating the temperature. The saturated conversion efficiency was around 13%, while with the effects of losses considered, the efficiency dropped to values ranging from 3 to 7%, with a peak value around 9%.