425 results about "Terahertz radiation" patented technology

A method for the high power generation and detection of terahertz radiation is presented. It comprises of an optical waveguide with a core, and a mostly hollow cladding or terahertz wave transparent material surrounding the core. The cladding region is a terahertz waveguide. A pump light source is coupled to the core to promote nonlinear optical process, such as Raman scattering, in the core which in turn leads to terahertz radiation being emanated or received through fiber cladding.

A terahertz spectrometer having a wider range of terahertz radiation source, high temporal resolution of scanning (<0.0.099 μm or ˜0.3 pico second) over a wider range of scanning (up to ˜100 pico seconds). Also disclosed are exemplary applications of the spectrometer in biomedical, biological, pharmaceutical, and security areas.

A system to detect an article includes one or more terahertz modules. Each module either generates or receives, or both generates and receives, terahertz radiation. Some of the terahertz radiation is reflected from the article and the remainder of the terahertz radiation is transmitted through the article. A processor analyzes the reflected and transmitted terahertz radiation to characterize the article.

A direct detector for terahertz radiation comprises a grating-gated field-effect transistor with one or more quantum wells that provide a two-dimensional electron gas in the channel region. The grating gate can be a split-grating gate having at least one finger that can be individually biased. Biasing an individual finger of the split-grating gate to near pinch-off greatly increases the detector's resonant response magnitude over prior QW FET detectors while maintaining frequency selectivity. The split-grating-gated QW FET shows a tunable resonant plasmon response to FIR radiation that makes possible an electrically sweepable spectrometer-on-a-chip with no moving mechanical optical parts. Further, the narrow spectral response and signal-to-noise are adequate for use of the split-grating-gated QW FET in a passive, multispectral terahertz imaging system. The detector can be operated in a photoconductive or a photovoltaic mode. Other embodiments include uniform front and back gates to independently vary the carrier densities in the channel region, a thinned substrate to increase bolometric responsivity, and a resistive shunt to connect the fingers of the grating gate in parallel and provide a uniform gate-channel voltage along the length of the channel to increase the responsivity and improve the spectral resolution.

The invention provides a terahertz plane adsorbing material, belonging to the technical field of electromagnetic function materials and relating to an electromagnetic-wave absorbing material. The terahertz plane adsorbing material comprises a substrate, a metal reflecting layer, a dielectric layer and an artificial electromagnetic medium layer; wherein, the metal reflecting layer is a continuous metal film and is arranged on the surface of the substrate; the dielectric layer is arranged between the metal reflecting layer and the artificial electromagnetic medium layer; the artificial electromagnetic medium layer is composed of artificial electromagnetic medium units which are arrayed periodically, each unit is a centro-symmetric figure formed by metal film lines with line width which is t and comprises two sing-opening metal rings which are connected backwards with long edges at two sides of an electric snap ring resonator. The terahertz plane adsorbing material provided by the invention has two strong-absorption frequency ranges, so as to provide selective adsorption and detection at different frequency ranges, and the terahertz radiation with wider spectral range can be adsorbed, so as to improve the performance and efficiency of the terahertz plane adsorbing material.

The invention provides a terahertz radiation detector. The terahertz radiation detector comprises a terahertz sensitive structure and a substrate chip including a reading circuit, wherein the terahertz sensitive structure comprises a terahertz absorption structure, a heat conversion layer and a protection layer, when passive / active terahertz waves are focused on the terahertz sensitive structure through a terahertz object lens, absorbed energy is converted into heat energy through the terahertz absorption structure, the heat energy is converted into an electric signal through the heat conversion layer, and the electric signal is read through the reading circuit on the substrate chip. According to the terahertz radiation detector, a terahertz micro-bolometer micro-bolometer operates under a non-refrigeration environment, single point detection can be carried out, terahertz imaging can further be realized through a focal plane array.

A system and method for using terahertz radiation to detect and monitor a substance undergoing a change in phase from a liquid phase to a solid phase or vice-versa is disclosed. By employing terahertz radiation in either the pulsed mode or in the continuous-wave (CW) mode, the system can non-invasively monitor these changes. The system uses the principle that matter in a liquid state will absorb and attenuate terahertz radiation to a larger degree than matter in a semisolid or solid state. Most terahertz radiation absorption occurs due to the rotational motions of molecules, i.e. either whole molecules or groups of atoms rotating about molecular bonds.

This invention relates to apparatus and methods for sensing terahertz radiation, in particular over an area, and to terahertz radiation imaging systems. A terahertz radiation sensor, the sensor comprising an optical beam input to receive an optical probe beam, a detector to modulate said probe beam responsive to terahertz radiation, and a photosensitive detector to provide an output responsive to said probe beam modulation. The sensor being configured to provide a first optical path between said optical beam input and said electro-optic detector and to provide a second optical path between said electro-optic detector and said photosensitive detector, and wherein said sensor further comprises a polarizer, said polarizer being located in both said first and said second optical paths. We further describe imaging systems for use with such a probe.

Methods and apparatus for detecting variations in electromagnetic fields, in particular, terahertz (THz) electromagnetic fields, are provided. The methods and apparatus employ polarization detection devices and controllers to maintain or vary the polarization of modulated signals as desired. The methods and apparatus are provided to characterize electromagnetic fields by directing the electromagnetic field and a probe beam upon an electro-crystal and detecting the modulation of the resulting probe beam. Detection of the modulation of the probe beam is practiced by detecting and comparing the polarization components of the modulated probe beam. Aspects of the invention may be used to analyze or detect explosives, explosive related compounds, and pharmaceuticals, among other substances. A compact apparatus, modular optical devices for use with the apparatus, sample holders, and radiation source mounts are also disclosed.

Although THz radiation is naturally emitted by hot objects, the intensity levels are too weak to be considered as a practical THz source for most applications. Photonic crystal structures are used to modify the thermal emission peak associated with the standard Planck blackbody spectral distribution so that the THz region is dramatically enhanced. The photonic crystal core is preferably combined with variable Q defect cavities and a wave guiding and power combining structure so that the radiated THz energy is efficiently collected and directed to an output antenna. Higher THz emissions are realized by embedding a finer (higher frequency) photonic crystal structure within a coarser (lower frequency) structure.

Method and apparatus of analyzing a fluid from an earth formation using a downhole tool. In the method, the downhole tool is conveyed down a borehole in the earth formation, and a fluid drawn into a measurement portion of the downhole tool, where a spectroscopic measurement of the fluid is made in a terahertz radiation domain. The method may be part of a method of producing a mineral hydrocarbon material from an earth formation.

The invention discloses a graphene terahertz wave detector. The graphene terahertz wave detector comprises a graphene field effect transistor and an antenna which can be effectively coupled to terahertz waves. The antenna is in integrated arrangement with the graphene field effect transistor yet is completely independent from the source electrode and the drain electrode of the graphene field effect transistor. According to the invention, through combination between a top grid and a back grid, the transport property of a graphene two-dimensional electron gas is effectively regulated and controlled, and accordingly, the terahertz waves are detected. The two sides of the top grid of the graphene field effect transistor are integrated with a plane antenna which is independent from the source electrode and the drain electrode and can be highly efficiently coupled to the terahertz waves, such that terahertz wave signals are coupled to a grid electrode in the form of capacitance, and the response of the graphene detector to terahertz radiation can be effectively enhanced. The detector can generate photoelectric currents or open-circuit voltages under radiation of the terahertz waves so as to realize room-temperature, high-speed, high-efficiency, high-sensitivity and low-noise detection.

The present invention relates to security label (12) for securing or authenticating goods or services or a security document. Currently radio frequency ID cards, having an inductive loop and a microchip containing security information, are used. However, such RF ID cards are expensive to manufacture. Therefore it is proposed to use a security label or document (12) including a terahertz image or tag (14, 15, 76) which may beta hologram. Security information can then be read by reflection or transmission of terahertz radiation which is not visible to the unaided eye. The terahertz image or tag may be covered by a material (66, 68) opaque to visible light, but transparent or transmissive of terahertz wavelengths, making it difficult for potential fraudsters to investigate the terahertz image. A method of making such a security label or document, a security or authentication method and system using terahertz radiation are also disclosed.

A security mark (130) that comprises a metamaterial such that properties of the metamaterial provides authentication of the security mark (130). The metamaterial may have a negative refractive index. An article may be secured by applying the metamaterial to the article such that properties of the metamaterial authenticate the article. The metamaterial may be arranged to form an image (160) when illuminated by terahertz radiation.

A terahertz time-domain spectroscopic ellipsometry system includes a sample stage, a terahertz emitter configured to provide pulses of terahertz radiation with preselected polarization components to illuminate a sample on the sample stage along an incident direction, and a coherent terahertz detection system arranged to coherently detect pulses of terahertz radiation from the terahertz emitter along an emerging direction after at least one of reflecting from or passing through the sample. The sample stage is rotatable to vary a relative angle between the incident direction and the emerging direction, and the coherent terahertz detection system substantially maintains alignment for amplitude and polarization detection as the relative angle is varied.

A terahertz radiation mixer comprises a heterodyned field-effect transistor (FET) having a high electron mobility heterostructure that provides a gatable two-dimensional electron gas in the channel region of the FET. The mixer can operate in either a broadband pinch-off mode or a narrowband resonant plasmon mode by changing a grating gate bias of the FET. The mixer can beat an RF signal frequency against a local oscillator frequency to generate an intermediate frequency difference signal in the microwave region. The mixer can have a low local oscillator power requirement and a large intermediate frequency bandwidth. The terahertz radiation mixer is particularly useful for terahertz applications requiring high resolution.

The invention is a method and apparatus for the detection of terahertz radiation. In one embodiment, frequency modulated spectroscopy is performed on a swept source of coherent far infrared electromagnetic radiation that is focused on a target. A beam of radiation passes through a cell in which the target is housed, losing energy as certain frequencies are absorbed by contaminants in the target. A detector is positioned to determine how much energy is lost by the radiation (e.g., which frequencies fail to transmit through the cell), thereby indicating the presence of contaminants in the target.

Terahertz metamaterials comprise a periodic array of resonator elements disposed on a dielectric substrate or thin membrane, wherein the resonator elements have a structure that provides a tunable magnetic permeability or a tunable electric permittivity for incident electromagnetic radiation at a frequency greater than about 100 GHz and the periodic array has a lattice constant that is smaller than the wavelength of the incident electromagnetic radiation. Microfabricated metamaterials exhibit lower losses and can be assembled into three-dimensional structures that enable full coupling of incident electromagnetic terahertz radiation in two or three orthogonal directions. Furthermore, polarization sensitive and insensitive metamaterials at terahertz frequencies can enable new devices and applications.

A multispectral sensor which includes a complementary metal oxide semiconductor substrate having a switching circuit, at least one antenna-receiving combination device for detecting terahertz radiation, at least one additional bolometer for detecting mid-range infrared radiation, and at least one diode for detecting radiation in the visible to near-infrared range. A multispectral imaging and / or spectroscopy system, a method for detecting and / or examining life forms, objects, and materials using such a system, and the use of such a sensor and system are also described.

This invention relates to apparatus and methods for sensing terahertz radiation, in particular over an area, and to terahertz radiation imaging systems.A terahertz radiation sensor, the sensor comprising an optical beam input to receive an optical probe beam, a detector to modulate said probe beam responsive to terahertz radiation, and a photosensitive detector to provide an output responsive to said probe beam modulation. The sensor being configured to provide a first optical path between said optical beam input and said electro-optic detector and to provide a second optical path between said electro-optic detector and said photosensitive detector, and wherein said sensor further comprises a polarizer, said polarizer being located in both said first and said second optical paths. We further describe imaging systems for use with such a probe.

The invention relates to a MMAOP framework applicable to a terahertz radar and communication system. The implementation mode that a multiplier, a mixer, an array, the quasi-optics and a parabolic antenna are combined is adopted for the MMAOP framework, an all-solid high-power terahertz radiation source is obtained, and meanwhile the MMAOP framework is applicable to the terahertz radar and communication system. A receiving link and a transmitting link of the framework are both obtained in an all-solid mode, and thus the MMAOP framework is good in repeatability and can be integrated and be smaller conveniently. According to the framework, the output power of the terahertz source is raised with an array space power synthesis method, and thus the expansibility is good; a small array can be adopted first to acquire medium output power, as the technology improves, the number of arrays is gradually increased, the output power of a single array element is raised, and thus the radiation power is raised.

A method for generating terahertz radiation includes inducing a background plasma in a volume of a gas by focusing a first optical beam in the volume, and generating pulsed terahertz radiation with enhanced generation efficiency by focusing a second time-delayed optical beam in the background plasma. The method may be implemented in a system for detecting and analyzing a remotely-located object.

Systems, configurations and methods of using an ultrafast, self-starting, mode-locked laser are provided. The systems, devices and methods of using stable, self-starting mode-locked lasers, can be compact, use fewer optical elements and have energies sufficient for most micro-processing and micro-structuring applications. The large spectral bandwidth of ultra-short (femtosecond) laser pulses can be used in laser sensing applications, micro-machining, time-resolved experiments, where short-lived transient species can be observed in biological or chemical reactions. Terahertz radiation can be generated using ultrashort pulses and used for imaging applications.

The invention discloses a terahertz radar ISAR imaging method. The terahertz radar ISAR imaging method comprises the following steps of carrying out untangle frequency modulation on received echo signals, carrying out Fourier transform on distance-oriented echoes of the echo signals, analyzing the echo signals at a time domain, structuring a kernel function, extracting all parameters of the echo signals on non-linear second-order chirp signals of azimuth-oriented echoes, structuring a penalty function, carrying out motion compensation, and carrying out FFT on the obtained azimuth-oriented echoes to obtain two-dimensional images. According to the terahertz radar ISAR imaging method, high-order chirp signals can be processed, matching search is only carried out in a two-dimensional space for estimating consumed cost, calculation complexity is not high, and the terahertz radar ISAR imaging method is suitable for terahertz radar imaging.

A pulse source generates both terahertz radiation (T-rays) and X-rays consecutively at high peak intensity using the same electron beam generated in an RF photoinjector and two different extractors / radiators for the T- and X-rays.

Although THz radiation is naturally emitted by hot objects, the intensity levels are too weak to be considered as a practical THz source for most applications. Photonic crystal structures are used to modify the thermal emission peak associated with the standard Planck blackbody spectral distribution so that the THz region is dramatically enhanced. The photonic crystal core is preferably combined with variable Q defect cavities and a wave guiding and power combining structure so that the radiated THz energy is efficiently collected and directed to an output antenna. Higher THz emissions are realized by embedding a finer (higher frequency) photonic crystal structure within a coarser (lower frequency) structure.

An apparatus and method are disclosed for detecting terahertz radiation at room temperature. A detecting pixel includes a sub-wavelength split-ring resonator, and is mechanically coupled to (but thermally decoupled from) a substrate via a cantilever formed from two materials that have a significant mismatch in their thermal expansion coefficients. Incident radiation causes the split-ring resonator to resonate, thereby generating heat that is transferred to the cantilever, causing the cantilever to flex. An optical readout system includes a secondary light source, such as a laser, that shines on a reflective surface on the pixel, whereby a photodiode detects the reflected light and permits calculation of a relative deflection of the pixel in the nanometer range. An exemplary detector has a noise equivalent power rating of approximately 60 pW / √Hz.

A Terahertz wave radiation source belongs to the technical field of Terahertz wave. The basic structure comprises a microwave source, a connecting wave guide and a Terahertz wave generator. The Terahertz wave generator works in a vacuum state in a tube, and mainly comprises a cathode for emitting electrons, a focusing electrode, a microwave input wave guide, a microwave cavity, an electron beam drifting and bunching pipe, an extraction electrode, a thick film capacitor, a thin film radiating antenna, an electron beam focusing magnet and a pole shoe. The invention has a simple structure, the output power and efficiency greatly exceeding that of the prior Terahertz wave generator, is suitable for large-scaled production, and has wide application prospect in the fields, such as material detection, human body imaging, component analysis, and the like.