Extension of tunable far-infrared spectroscopy to 7.9THz

Waveguided Approach for Difference Frequency Generation of Broadly-Tunable Continuous-Wave Terahertz Radiation

The 1–10 terahertz (THz) spectral window is emerging as a key region for plenty of applications, requiring not yet available continuous-wave room-temperature THz spectrometers with high spectral purity and ultra-broad tunability. In this regard, the spectral features of stabilized telecom sources can actually be transferred to the THz range by difference frequency generation, considering that the width of the accessible THz spectrum generally scales with the area involved in the nonlinear interaction. For this reason, in this paper we extensively discuss the role of Lithium Niobate (LN) channel-waveguides in the experimental accomplishment of a room-temperature continuous wave (CW) spectrometer, with μW-range power levels and a spectral coverage of up to 7.5 THz. To this purpose, and looking for further improvements, a thought characterization of specially-designed LN waveguides is presented, whilst discussing its nonlinear efficiency and its unprecedented capability to handle high optical power (107 W/cm2), on the basis of a three-wave-mixing theoretical model.

Generation of tunable far-infrared radiation with a quantum cascade laser

We demonstrate the generation of cw tunable far-infrared radiation by mixing a quantum cascade laser and a CO>(2) laser in a W-Ni metal-insulator-metal diode. The first known spectroscopic application to the recording of an H(79)Br transition near 4.47 THz is reported.

Tunable far-infrared spectroscopy extended to 9.1THz

We synthesized tunable far-infrared radiation at frequencies higher than 9 THz (300 cm (-1)) by mixing CO(2) laser, (15)NH(3) laser, and microwave radiation in a W-Co metal-insulator-metal diode. We used this farinfrared radiation to accurately measure torsion-rotation transitions of CH(3)OH in the 8-9-THz region. We also measured the frequency of the aP(7, 3) (15)NH(3) laser transition.