THz-wave Parametric Oscillator Research Articles

A frequency-agile terahertz-wave parametric oscillator

We demonstrated a pulse-to-pulse frequency-tunable LiNbO3 terahertz-wave parametric oscillator, pumped with a Q-switched Nd:YAG laser. Rapid tuning from 1 to 2 THz, with random frequency accessibility, was achieved by rotating the pump beam angle using an optical beam scanner and a telescope.

Injection-seeded terahertz-wave parametric oscillator

The narrow linewidth operation of a THz-wave parametric oscillator was achieved through the use of narrow linewidth laser injection. THz-wave parametric oscillation, generated by a LiNbO3 crystal pumped with a single longitudinal mode Q-switched Nd:YAG laser, was injection seeded with a continuous-wave Yb:fiber laser. The measured THz-wave linewidth was 200 MHz, which corresponded to the measurement resolution limit.

A Continuously Tunable Ring-Cavity THz-Wave Parametric Oscillator.

We demonstrate a widely tunable terahertz (THz) -wave parametric oscillator (TPO) in a ring cavity configuration using a novel frequency-tuning method involving rotating a single mirror forming the cavity. The TPO consisted of a nonlinear optical MgO: LiNbO3 crystal in a three-mirror ring cavity. We obtained continuous tuning of THz-wave in the 0.93 to 2.7 THz range by adjusting the mirror. The maximum THz-wave output of 69.6 pJ/pulse at 1.3 THz was coupled out from a single Si prism coupler. The absorption of HCl gas was measured in order to check the tuning controllability. The high performance of the TPO was confirmed from the transmission dip of the measured spectrum in agreement with the known center absorption lines.

Tunable terahertz-wave parametric oscillators using LiNbO/sub 3/ and MgO:LiNbO/sub 3/ crystals

Coherent tunable terahertz waves were generated successfully using a terahertz-wave parametric oscillator (TPO) based on laser light scattering from the A/sub 1/-symmetry polariton mode of LiNbO/sub 3/. This method has several advantages, such as continuous and wide tunability (frequency: 0.9-3.1 THz), a relatively high peak power (more than a few milliwatts), and compactness of its system (tabletop size). In addition, the system simply requires a fixed-wavelength pump source and it is easy to tune. This paper deals with the general performance of this terahertz-wave source using the prism output-coupler method as well as the development and applications of the system. Its tunability, coherency, power, and polarization were measured, and this tunable source was used for terahertz spectroscopy to measure the absorption spectra of LiNbO/sub 3/ and water vapor. Also, the use of MgO-doped LiNbO/sub 3/ (MgO:LiNbO/sub 3/) in our terahertz regime, as well as its far-infrared properties, is described. We found that the MgO:LiNbO/sub 3/ TPO is almost five times more efficient than the undoped LiNbO/sub 3/ TPO, and we have proven that the enhancement mechanism originates from the enhanced scattering cross section of the lowest A/sub 1/-symmetry mode in a spontaneous Raman experiment.