A new scheme for the intracavity generation of terahertz radiation in femtosecond mode-locked Ti:Sapphire lasers is presented. The scheme combines advantages of a fast saturable semiconductor Bragg mirror with that of a photoconductive THz emitter. It significantly increases the efficiency of the intracavity THz generation. In addition, the output THz radiation can be electrically modulated at ...

28 Scientists have spent the last century or so busily plundering the electromagnetic spectrum, adapting almost every wavelength possible for all manner of applications. We listen to music through radio waves , cook our dinners using microwaves, turn our televisions on with infrared lasers, find forged bank notes with ultraviolet light and identify broken bones with X-rays. Yet there is one reg...

To enhance terahertz emission from an optically excited semiconductor surface, we propose to sandwich a thin (as compared to the terahertz wavelength) semiconductor layer between a dielectric hyperhemispherical lens and metal substrate. The layer is excited through the lens. The substrate provides constructive interference of terahertz waves emitted to the lens directly from the layer and refle...

We tested the hypothesis that polarization sensitive optical and terahertz imaging may be combined for accurate nonmelanoma skin cancer (NMSC) delineation. Nine NMSC specimens were imaged. 513 μm and 440 nm wavelengths were used for terahertz and optical imaging, respectively. Histopathology was processed for evaluation. Terahertz reflectance of NMSC was quantified. Our results demonstrate that...

Antenna-coupled photomixers, serving as emitters and receivers of terahertz (THz) radiation, are the central active components coherent optoelectronic THz systems. Here, we focus on continuous-wave modality, which finds ample use for spectroscopy, sensing, ranging plays a major role in upcoming ultrahigh-frequency telecommunication applications. We demonstrate with planar based low-temperature-...

Microfabricated electron emitters have been studied for half a century for their promising applications in vacuum electronics. However, tunable microfabricated electron emitters with fast temporal response and controllable electron emission still proves challenging. Here, we report the scaling down of thermionic emitters to the microscale using microfabrication technologies and a Joule-heated m...

We report the use of a terahertz pulsed imaging technique for three-dimensional chemical mapping. Terahertz radiation reflected from a sample was measured pixel-by-pixel in time domain using a terahertz pulsed imaging system developed at TeraView Ltd, UK. The recorded terahertz waveforms were then transformed into frequency domain using time-partitioned Fourier transform. Structural maps of sam...

The hottest frequency region in terms of research currently lies in the 'frequency gap' region between microwaves and infrared: terahertz waves. Although new methods for generating terahertz radiation have been developed, most sources cannot generate high-brightness terahertz beams. Here we demonstrate the generation of ultrabright terahertz waves (brightness ~0.2 GW/sr·cm(2), brightness temper...

We propose a scheme for an experimental verification of the reversed Cherenkov effect in left-handed media. The scheme uses optical-to-terahertz conversion in a planar sandwichlike structure that consists of a nonlinear core cladded with a material that exhibits left-handedness at terahertz frequencies. The focused into a line femtosecond laser pulse propagates in the core and emits Cherenkov w...