Tunable terahertz parametric oscillator synchronously pumped by mode-locked picosecond Ti:Sapphire laser with MgO-doped LiNbO3

Abstract

A terahertz (THz) parametric oscillator (TPO), which was based on the optical parametric process, in a doubly-resonant external enhancement cavity synchronously-pumped by a mode-locked picosecond Ti:sapphire laser with the center wavelength of 780 nm and the average output power of 850 mW, was built. Our TPO cavity including four mirrors and a 5 mol% MgO-doped LiNbO₃ (MgO:LN) crystal with Si-prism couplers for the output coupling of the THz wave was designed so as to circulate both pump and idler waves in the same cavity simultaneously. Furthermore, we utilized a Hänsch-Couillaud method to stabilize the cavity. As a result, we developed an easily and continuously tunable picosecond TPO by changing the noncollinear phase-matching condition. The tunable wavelength range of the idler wave was from 782 to 787 nm, which corresponded to the THz frequency range from 1.0 to 3.4 THz according to the law of energy conservation. In addition, the measured angle between the pump and idler waves, which varied from 0.6 to 2.5 degrees, showed a good agreement with the theoretical calculation of the noncollinear phase-matching condition in all the above tuning range.