35results about "Charged particle masers" patented technology

A terahertz imaging system uses a terahertz light source to illuminate a target object with a series of short pulses of terahertz light. The pulses have a low average output power but a high peak output power, thereby enabling imaging of the suspicious object or person at a safe distance while avoiding injury to the person being imaged. For each pulse, the reflection of the light is imaged by a detector array. The terahertz light pulses are individually narrow band and the emitted pulse train is rapidly tuned in wavelength across a wide frequency range in the terahertz band. Within the terahertz frequency range, molecules have unique absorption spectra. The energy reflected from the illuminated threat object is measured for each of the discrete narrow frequency bands and compared to the absorption spectra of known dangerous materials to determine whether the threat object contains or carries a known dangerous material.

A method and apparatus for minimizing the degradation of power in a free electron laser (FEL) generating terahertz (THz) radiation. The method includes inserting an absorber ring in the FEL beam path for absorbing any irregular THz radiation and thus minimizes the degradation of downstream optics and the resulting degradation of the FEL output power. The absorber ring includes an upstream side, a downstream side, and a plurality of wedges spaced radially around the absorber ring. The wedges form a scallop-like feature on the innermost edges of the absorber ring that acts as an apodizer, stopping diffractive focusing of the THz radiation that is not intercepted by the absorber. Spacing between the scallop-like features and the shape of the features approximates the Bartlett apodization function. The absorber ring provides a smooth intensity distribution, rather than one that is peaked on-center, thereby eliminating minor distortion downstream of the absorber.

The embodiment of the invention provides a terahertz radiator based on stimulated amplification coherent Smith-Purcell radiation, and the terahertz radiator comprises an electron emission source whichis used for emitting an electron beam; a pumping source, used for emitting a pumping signal, and the pumping signal interacting with the primary grating structure to obtain primary cluster electrons.The preliminary cluster electrons interact with the primary grating structure to generate coherent Smith-Purcell radiation. Vertical resonance with a pumping signal is carried out in the first-stageresonant cavity structure, so that the electron bunching density is increased, and the coherent Smith-Purcell radiation is enhanced. A positive feedback process is formed by the free electrons and thecoherent Smith-Purcell cell radiation, and the stimulated and amplified coherent Smith-Purcell cell radiation and periodic cluster electron groups are obtained. The terahertz radiator provided by theembodiment of the invention can realize the stimulated amplification phenomenon under the conditions of small current and large beam spots.

Provided is a linearly polarized ultra-short terahertz wave generating device which has a parabolic barrel mirror installed at one side of a multiple thin film, to generate an ultra-short terahertz wave having single linear-polarized light and uniformly formed output distribution.

The invention discloses a microwave source, and the microwave source comprises a semiconductor laser, a photoelectric modulator, a first optical coupler, a first polarization controller, a second polarization controller, a second optical coupler, a resonant cavity module, an optical detector, a filter and a directional coupler, wherein the semiconductor laser, the photoelectric modulator and the first optical coupler are sequentially connected along an optical path; one output end of the first optical coupler is connected with the input end of the first polarization controller, and the other output end of the first optical coupler is connected with the input end of the second polarization controller; the output end of the first polarization controller is connected with one input end of thesecond optical coupler; the output end of the second polarization controller is connected with the other input end of the second optical coupler; the second optical coupler, the resonant cavity module, the optical detector, the filter and the directional coupler are connected in sequence; and the directional optical coupler is connected with the photoelectric modulator. According to the invention, the extremely low phase noise can be obtained, the spurious wave suppression level is good, the cost is low, and the optical path adjustment is simple.

A method for managing the broad band microwave and TeraHertz (THz) radiation in a free electron laser (FEL) having a wiggler producing power in the electromagnetic spectrum. The method includes placement of broadband microwave and TeraHertz (THz) radiation absorbers on the upstream end of the wiggler. The absorbers dampen the bounced back, broad band microwave and THz radiation returning from the surfaces outside the nose of the cookie-cutter and thus preventing broadening of the electron beam pulse's narrow longitudinal energy distribution. Broadening diminishes the ultimate laser power from the wiggler. The broadband microwave and THz radiation absorbers are placed on either side of the slot in the cookie-cutter that shapes the wake field wave of the electron pulse to the slot shape of the wiggler chamber aperture. The broad band microwave and THz radiation absorber is preferably a non-porous pyrolytic grade of graphite with small grain size.

An embodiment of the present invention provides a terahertz radiator based on stimulated amplified coherent Smith-Purcell radiation, including: an electron emission source, used to emit electron beams; a pump source, used to emit a pump signal, and the pump signal and The first-level grating structure interacts to obtain preliminary group electrons; the preliminary group electrons interact with the first-level grating structure to generate coherent Smith-Purcell radiation; vertically resonate with the pump signal in the first-level resonant cavity structure, making the electron group The density increases, which in turn enhances the coherent Smith-Purcell radiation; free electrons and coherent Smith-Purcell radiation form a positive feedback process, resulting in stimulated and amplified coherent Smith-Purcell radiation and periodic grouping of electron clusters. The terahertz radiator provided by the embodiment of the present invention can realize the phenomenon of stimulated amplification under the condition of small current and large beam spot.

A method and apparatus for generating terahertz waves using laser plasma are disclosed herein. The method of generating high-power terahertz waves includes generating plasma by focusing a laser beam on a gas within a vacuum chamber, radiating laser beams into the magnetized plasma from opposite directions so that the laser beams collide with each other at a preset location, and generating terahertz waves of a predetermined frequency through the oscillation of the plasma generated by the collision of the laser beams.