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High power and spectral purity continuous-wave photonic THz source tunable from 1 to 4.5 THz for nonlinear molecular spectroscopy

: Kiessling, Jens; Breunig, Ingo; Schunemann, P.G.; Buse, Karsten; Vodopyanov, K.L.

Postprint (PDF; )

New journal of physics. Online journal 15 (2013), No.10, Art. 105014, 11 pp.
ISSN: 1367-2630
Journal Article, Electronic Publication
Fraunhofer IPM ()
quantum optics; photonic crystal lasers; optical parametric oscillators; OPO

We report a diffraction-limited photonic terahertz (THz) source with linewidth <10 MHz that can be used for nonlinear THz studies in the continuous wave (CW) regime with uninterrupted tunability in a broad range of THz frequencies. THz output is produced in orientation-patterned (OP) gallium arsenide (GaAs) via intracavity frequency mixing between the two closely spaced resonating signal and idler waves of an optical parametric oscillator (OPO) operating near lambda = 2 µm. The doubly resonant type II OPO is based on a periodically poled lithium niobate (PPLN) pumped by a single-frequency Yb:YAG disc laser at 1030 nm. We take advantage of the enhancement of both optical fields inside a high-finesse OPO cavity: with 10 W of 1030 nm pump, 100 W of intracavity power near 2 µm was at tained with GaAs inside cavity. This allows dramatic improvement in terms of generated THz power, as compared to the state-of-the art CW methods. We achieved >25 µW of single-frequency tunable CW THz output power scalable to >1 mW with proper choice of pump laser wavelength.