Thursday, February 26, 2015
Abstract-Engineered phase matching for broad frequency-tunability in terahertz-wave generation from quasi-phase-matched GaP devices
A method to obtain broad frequency-tunability in terahertz (THz)-wave is proposed using a quasi-phase-matched device that originally has narrow frequency-tunability. In this method, the phase matching curve for the device is engineered via the by shifting the signal frequency to 333.1 THz (0.90 m) so that a flat part (i.e., a frequency-independent part) can be formed on the phase matching curve. By selecting an appropriate quasi-phase matching (QPM) period Λ such that QPM occurs at the center of the flat part of the curve, we can obtain a frequency-tunable width of 1.34 THz (37.8 m) at around a THz-wave frequency of 3.26 THz (92.0 m). This width is 9.9 times wider than that obtained using a similar quasi-phase-matched device at a signal frequency of 193.5 THz (1.55 m) without the reformed phase matching curve. The advantage of the proposed method is that, unlike a previous method that used a chirped (2) broad frequency-tunability is obtained without reducing the high conversion efficiency produced by QPM. For comparison, a reduction in the conversion efficiency for the chirped (2) method is demonstrated when a 9.9 times wider frequency-tunable width is achieved.