Generation of CW terahertz radiation using two-colour laser with Fabry-Perot etalon

Dual wavelength titanium:sapphire laser

“…As in a standard BRF the bandwidth of the transmitted peak is determined by the number of passes through the filter, which can be selected in a laser cavity depending on the photon lifetime defined by the cavity mirrors reflectivity. As a consequence of this deviation there is a reduction in the overall transmission of the BRF at the two selected wavelengths, which is an undesired, but tolerable effect [7,8]. …”

Generation of Terahertz radiation with two color semiconductor lasers

“…Unfortunately these two optical modes could not be tuned independently. A continuous spectral tuning ability from 0.1 up to 2 THz was realised by Naftaly et al using an etalon which could be tuned in length [21]. Leitenstorfer et al developed a modelocked Ti:S system for spectrally resolved pump-probe experiments [22].…”

“…E 2 (t) consists of a fast oscillation with the frequency (f 1 + f 2 )/2 which is modulated with an envelope function modulated with the difference frequency ν 21 = f 1 − f 2 . The generated carriers in the semiconductor cannot follow the fast oscillation at (f 1 + f 2 )/2, so that the generation rate of the carriers is proportional to the difference frequency ν 21 . When further a semiconductor with a low carrier lifetime is chosen for the photomixer, the carrier density in the photomixer exited by the beat signal also oscillates with the difference frequency.…”

“…3. So the photogenerated carriers in the photomixer are accelerated and give rise to a current I(t) modulated with the difference frequency ν 21 . This current is feeding the antenna structure deposited on the photomixer and thus gives rise to an emitted THz wave oscillating with the difference frequency of the two driving optical modes.…”

Analysis and design of a continuous-wave terahertz photoconductive photomixer array source

“…Photomixers are promising continuous-wave terahertz sources as potentially compact, low-power-consuming, coherent, low-cost, and tunable sources [21]- [28]. A terahertz photomixer is a heterodyne scheme, in which output of two single-mode lasers or output modes of a dual-mode laser with their frequency difference falling in the terahertz range mix in a nonlinear medium, such as a photoconductor [27], [29] or a superconductor [30], and generate a signal, whose frequency is equal to the frequency difference of the two lasers or two modes of the dual-mode laser.…”