摘要:
An apparatus and method for optical heterodyne conversion and a radiation source and integrated diagnostics using the apparatus and method are disclosed. The radiation source can operate in a high-power narrow-band mode in which a constant-frequency output is provided or in a low-power broadband mode in which the frequency is tunable to allow the radiation source to act as a sweep oscillator. The apparatus or photomixer includes two sets of interdigitated conductive electrodes formed on top of a crystal lattice formed of column III-V compounds, particularly InAlGaAs compounds. Additional column V atoms are interspersed within the lattice structure to form defect energy states in the bandgap of the host material. The region of the material between the interdigitated electrodes is illuminated by optical radiation containing two different frequencies. Photon absorption in the material causes a current at the difference frequency to be generated and coupled to the interdigitated electrodes. The current is then coupled to a planar transmission line or antenna structure to generate coherent, continuous-wave, unimodal radiation in the microwave, millimeter-wave, or submillimeter-wave regions.
摘要:
An optical correlator for correlating incident optical signals is described. The correlator comprises a transmission line in close juxtaposition to a photoconductor. The photoconductor may be positioned within the transmission line. The transmission line and the photoconductor may be monolithically integrated on a substrate. The optical correlator has an electrical non-linear response to the incident optical signals that results from a voltage divider formed from the combination of the transmission line and the photoconductor. The electrical non-linear response is proportional to a second-order intensity autocorrelation function g.sup.(2) (.tau.). The response time of the electrical nonlinear response is less than the width of the narrowest pulse of the optical signals and may be less than twenty picoseconds.
摘要:
Efficient transmission and reception of electromagnetic radiation are achieved by an antenna on a substrate. An antenna is fabricated on the top surface of a substrate which includes a periodic dielectric structure. The antenna operates at a frequency within the band gap of the periodic dielectric structure. Radiation emitted by the antenna cannot propagate through the structure and is therefore emitted only into space away from the substrate. When the antenna is receiving, radiation striking the device does not propagate through the substrate but is concentrated at the antenna. A phased array with isolated elements is achieved by fabricating the array elements on top of a substrate having a periodic dielectric structure and by surrounding the circuits associated with each antenna element with the periodic dielectric structure. Radiation from an element or associated circuitry at a frequency within the band gap of the structure cannot propagate into the substrate to interfere with other elements.
摘要:
Terahertz (THz) distributed detectors, and arrays of detectors that utilize structured surface plasmonic effects for more efficient coupling to free space are discussed. One example distributed detector includes a detector junction comprising a Schottky or tunneling interface between a semiconductor and a detector metal, an ohmic junction comprising an ohmic interface between the semiconductor and an ohmic metal, and a gap that separates the detector junction from the ohmic junction. Structured surface plasmons concentrate an electric field in the gap when the distributed detector is exposed to THz radiation polarized perpendicular to the gap.
摘要:
Terahertz (THz) distributed detectors, and arrays of detectors that utilize structured surface plasmonic effects for more efficient coupling to free space are discussed. One example distributed detector includes a detector junction comprising a Schottky or tunneling interface between a semiconductor and a detector metal, an ohmic junction comprising an ohmic interface between the semiconductor and an ohmic metal, and a gap that separates the detector junction from the ohmic junction. Structured surface plasmons concentrate an electric field in the gap when the distributed detector is exposed to THz radiation polarized perpendicular to the gap.
摘要:
Embodiments provide radio-frequency systems that can automatically detect, focus-on, and track objects in the environment without the need for expensive electronic scanning and phase-shifting components. Some embodiments are directed to retrodirective systems including: (1) quiescently broadcast pseudorandom-modulated radiation, such as pseudorandom bit sequences, in the absence of a target, over a field-of-view comparable to the beam solid angle of a single element in the transmit array; (2) a receive antenna element or array, in a desired spatial relationship with respect to the transmit antenna array, that receives reflected pseudorandom radiation from a target; and (3) an electronic signal-processing and feedback channel between the receive and transmit arrays that carries out cross-correlation between the received radiation and the transmitted pseudorandom signals and computes complex correlation coefficients to form a re-transmitted beam. Some embodiments are useful for short-range applications involving small and fast moving targets.
摘要:
A radiometer is described which coherently detects the thickness of oil films on water by converting continuous-frequency microwave or millimeter-wave brightness temperature versus frequency measurements from the frequency/wavenumber domain to the oil-film-thickness domain (received power versus film thickness).
摘要:
Gallium nitride based devices and, more particularly to the generation of holes in gallium nitride based devices lacking p-type doping, and their use in light emitting diodes and lasers, both edge emitting and vertical emitting. By tailoring the intrinsic design, a wide range of wavelengths can be emitted from near-infrared to mid ultraviolet, depending upon the design of the adjacent cross-gap recombination zone. The innovation also provides for novel circuits and unique applications, particularly for water sterilization.
摘要:
A hydration sensor is provided that includes a circulator having a plurality of ports, an amplitude-modulated coherent source connected to a first port of the circulator, a rectifier or other power sensor connected to a second port of the circulator followed by an RF baseband low-noise amplifier, a coupling structure connected to the third port of the circulator, and a demodulator connected to the output of the rectifier. The hydration sensor can include an RF low noise amplifier between the circulator and rectifier, and/or a second amplitude modulator between the circulator and the coupling structure. The coupling structure can be either a guided-wave near-field structure or an interfacial capacitive or inductive element. In the former case, the hydration is determined by measuring the reflectivity of the guided-wave radiation, and in the latter case it is determined by measuring the change of reflectivity (through change of impedance) of the interfacial element.
摘要:
RF and microwave radiation directing or controlling components are provided that may be monolithic, that may be formed from a plurality of electrodeposition operations and/or from a plurality of deposited layers of material, that may include switches, inductors, antennae, transmission lines, filters, and/or other active or passive components. Components may include non-radiation-entry and non-radiation-exit channels that are useful in separating sacrificial materials from structural materials. Preferred formation processes use electrochemical fabrication techniques (e.g. including selective depositions, bulk depositions, etching operations and planarization operations) and post-deposition processes (e.g. selective etching operations and/or back filling operations).