Line-narrowed, compact, and coherent source of widely tunable terahertz radiation

Abstract

We report a technique for line-narrowing terahertz radiation produced through parametric generation. By incorporating an etalon within the idler-wave cavity of the parametric oscillator, radiation is generated with a linewidth of 1GHz (freerunning linewidth 50–100GHz) and with a center frequency continuously tunable over a band >50GHz, settable anywhere within the coarse tuning range of the device (1–3THz). When implemented within an intracavity cavity geometry, pulses of terahertz radiation of duration ∼10ns and energy ∼30nJ are generated at repetition rates up to 400Hz (implying mean powers of >10μW and peak powers of ∼3W) in a compact device.

THz-wave generation via stimulated polariton scattering in KTiOAsO_4 crystal

“…But the critical angle resulting in the total reflection of the THz wave at the surface zx is less than 18.27°. So, extracting the THz wave from the crystal is a key problem like TPOs based on LiNbO 3 , where the arrayed Si-prism coupler [15,[17][18][19][20] and the surface-emitted configuration [16] are usually used. The surface-emitted configuration of the KTA-TPO is employed below.…”

“…They have many advantages, including operation at room temperature, compactness, widely tunable range and narrow linewidth [15]. However, in the past nearly 20 years, only crystal LiNbO 3 or MgO:LiNbO 3 [15][16][17][18][19][20] was used as the nonlinear material in TPOs. The generated THz-wave frequency range is from 0.6 to 3.2 THz.…”

Observation of a cascaded process in intracavity terahertz optical parametric oscillators based on lithium niobate

“…With simple optical components (off-axis parabolic reflector/cylindrical Teflon lens) the extracted THz radiation can be formed into a circularly symmetric beam of reasonable spatial quality (M 2 values in the range 1.5 to 2). Further, we have reported spectral linewidth reduction from typical linewidths of 50 GHz for the basic device to < 1GHz by using intracavity etalons [6], and to ≈ 100MHz by injection seeding techniques [7], while still retaining the full tuning range.…”

Continuous wave, frequency-tunable terahertz laser radiation generated via stimulated polariton scattering

“…The relatively broad linewidth of the fundamental field is attributed to the large number of longitudinal modes supported within the high-Q resonator. From these measurements, we inferred that the linewidth of the THz radiation was <72 GHz [24].…”