Compact source of continuously and widely-tunable terahertz radiation.

Abstract

We report a THz radiation source based on the technique of non-collinear phasematched parametric generation. The source, which is compact and operable at room temperature, generates nanosecond pulses of peak power and energy greater than 1W and 5 nJ respectively. The radiation is continuously tunable over the range 1.2-3.05 THz and is of narrow spectral bandwidth (<100 GHz). The use of intersecting pump and parametric wave cavities results in threshold pump pulse energies below 1 mJ (from a Nd:YAG laser excited at 20 W, 500 microsec by a quasi-CW diode-laser) and close to 50% down-conversion efficiency when operated at twice threshold.

Design of High-Performance Millimeter Wave and Sub-Millimeter Wave Quasi-Optical Isolators and Circulators

“…We have validated this at a number of spot frequencies and shows that practical high-performance QOFRs in quasi-optical isolators are feasible to frequencies of 500 GHz and beyond, where no alternatives exist. Indeed, recent measurements using a newly developed terahertz source [31] have shown that the Faraday effect still persists in hexaferrites at frequencies above 1 THz. Insertion loss becomes quite severe at these frequencies (more than 10 dB), but such devices may still be useful for some sub-millimeter spectroscopic applications, where measurement accuracy can be more limited by system standing waves than by other signal-to-noise considerations.…”

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

“…Typically the spectral width of the primary idler-wave, and hence the accompanying THz radiation, is ≈ 50GHz (FWHM). A fuller description of this device and its performance characteristics is given in [5].…”

“…Firstly the capability for angle tuning over a wide spectral range (0.5-4THz [5]) is retained; secondly the significant loss of the nonlinear coefficient resulting from quasi-phase matching is avoided and finally the use of separate cavities as opposed to one common cavity provides the flexibility required for individual cavity optimisation. It is therefore important that cascaded processes for further overcoming the Manley-Rowe limit continue to be explored in the context of THz devices based on the use of bulk lithium niobate combined with non-collinear phase matching geometries.…”

“…We previously reported a parametric device based on a novel intersecting cavity geometry [5] in which the nonlinear medium (MgO:LiNbO 3 ) used for the parametric generation of the terahertz radiation is located within the cavity of the pump laser, where it is subject to the high circulating intra-cavity field. Since this field is typically over an order of magnitude greater in intensity than the external field obtainable from the pump laser under optimum output coupling conditions, a device with a low oscillation threshold and significantly improved down-conversion efficiency results, while obviating the need for high-energy pump lasers.…”

Low Threshold, Wide Dynamic Range, Tunable, All-Optical Self-Modulator Based on Fano Resonance and Out-of-Plane Coupling in a Slab Photonic Crystal with a Graphene Layer

“…Up to now various optical and electrical methods have been used for THz sources [1][2][3][4][5][6][7][8][9][10][11]; however at present, achieving compact, efficient, and economic sources remains a challenge to scientists and engineers [11][12][13][14]. One of the main optical methods for CW THz wave generation is heterodyne method that uses THz beat frequency of two frequency-locked laser beams with two different frequencies [10,11].…”