750results about "Solid masers" patented technology

Masers and microwave amplifiers that can function in the continuous-wave mode at room temperature are provided. The maser system can include a diamond gain medium having nitrogen-vacancy centers, and a resonator can be disposed around the gain medium. The resonator can be disposed in a cavity box, and radiation (e.g., visible light) can be provided to the gain medium to cause emission of microwave radiation.

The invention discloses a stable photoelectric oscillator. The stable photoelectric oscillator comprises a laser device, an electro-optical modulator, a long optical fiber, a photoelectric detector, an amplifier, an electric band-pass filter, an electrically-controlled microwave phase shifter, a high-stability microwave source, a 2*1 wave combiner or directional coupler, a first 1*2 power divider or directional coupler, a second 1*2 power divider or directional coupler, a third 1*2 power divider or directional coupler and a phase locking control module, wherein the phase locking control module comprises a frequency mixer, an electric low pass filter and a servo control module, the output end of the frequency mixer is connected to the input end of the electric low pass filter, and the output end of the electric low pass filter is connected to the input end of the servo control module. According to the stable photoelectric oscillator, an electric injection of the external high-stability microwave source and a phase locking control mechanism are added based on a traditional single-loop OEO structure. Compared with the prior art, the stable photoelectric oscillator has the advantages that insertion loss of an optical link in a resonant cavity is not increased, the high signal to noise ratio of the photoelectric resonant cavity is maintained, and the structural complexity of the stable photoelectric oscillator is lower than that of an existing scheme. The stable photoelectric oscillator is easy to obtain.

The invention relates to the non linear optical frequency conversion. To realize output of high power THz wave which can be continuously tuned, and stable running at room temperature, the technical scheme used by the invention is that: a tunable terahertz radiation source based on difference frequency cherenkov effect is composed of a laser device, a frequency doubling crystal, a double wavelength parametric oscillator, a harmonic mirror, a polarization filter, a combined beam mirror, a column lens and a difference frequency crystal; the harmonic mirror is placed between the frequency doubling crystal and the double wavelength parametric oscillator; the double wavelength parametric oscillator is II type phase matching KTP (Potassium Titanyl Phosphate) crystal OPO (Optical Parametric Oscillator); the polarization filter, the combined beam mirror and the column lens are arranged between the parametric oscillator and the difference frequency crystal; the difference frequency crystal is amagnesium oxide doped lithium niobate crystal with molecular formula of MgO:LiNbO3 or MgO:LN, and the generated THz wave is coupled and output by an Si prism on the side surface of the difference frequency crystal. The tunable terahertz radiation source based on difference frequency cherenkov effect is mainly applied to the optical frequency conversion.

A method and a system are implemented in the fabrication of a portable high power terahertz beam source that can produce a tunable, high power terahertz beam over the frequency from 0.1 THz to 2.5 THz. The terahertz source employs a recycling pump beam method and a beam quality control device. The beam quality control device may or may not be required for a high power terahertz beam generation. In exemplary embodiments, a lithium niobate (LiNbO₃) crystal or a lithium niobate crystal doped with 5% magnesium oxide (LiNbO₃:MgO) can be used. Other nonlinear optical crystals, including GaSe can be used in place of the LiNbO₃ crystal. Through proper alignment of a pump beam, along with recycling a pump beam, high conversion efficiency is achieved, and a high output power beam is produced at terahertz frequencies.

The invention provides a broadband tuning terahertz wave generator based on ultrasonic grating frequency shift and cyclic frequency shift. The broadband tuning terahertz wave generator comprises a laser, a circulator, a beam splitter, a cyclic frequency shift link based on the ultrasonic grating frequency shift, a beam combiner, an optoisolator and a photoelectric converter with a terahertz radiating antenna; light output by the laser passes through the circulator and then is split into a first path and a second path by the beam splitter; the first path is reference light and the second path is input to the cyclic frequency shift link to generate cyclic frequency shift light; the reference light and the cyclic frequency shift light are superposed in the beam combiner to generate beat frequency light in the range of the terahertz frequency; and the generated beat frequency light is processed by the optoisolator and then is received by the photoelectric converter with the terahertz radiating antenna, and the photoelectric converter radiates coherent terahertz waves. The generator provided by the invention has small volume, easiness for integration due to fewer optical elements, large tuning scope, high tuning efficiency and high efficiency in generating terahertz.

A pulse laser apparatus includes a laser configured to generate a pulse of a laser beam, a fiber amplifier, and a pulse compressor. The fiber amplifier includes a rare-earth doped fiber that exhibits normal dispersion at a wavelength of the laser beam generated from the laser. The pulse laser apparatus further includes a unit configured to give a loss to energy portions in a wavelength region corresponding to a zero-dispersion wavelength of the rare-earth doped fiber and/or a wavelength region longer than the zero-dispersion wavelength within a wavelength spectrum of the laser beam having been chirped in the fiber amplifier.

The invention discloses terahertz wave generating device and method based on optical four-wave mixing effect, which belong to the technical field of microwave photonics. The method comprises the following steps of: driving an intensity modulator by a microwave source signal through electric frequency multiplication by using optical carrier suppression modulation of the external intensity modulator and the four-wave mixing effect in a nonlinear device, forming a carrier suppression signal with only two first-order side bands, then forming two new side bands through the nonlinear device, filtering the original first-order side bands by an optical filter, only retaining two new side bands and carrying out beat frequency on the two new side bands in a PD (Photo Detector) to generate a terahertz wave frequency with six frequency multiplications. The invention lowers the requirements of the microwave modulation signal frequency and the modulator band width and reduces the cost of a system, the generating device has simple structure and favorable portability and the generated terahertz wave has very high stability.

The invention discloses a laser wavelength adjustment-based opto-electronic oscillator with a tunable frequency and a tunable broadband. The opto-electronic oscillator is characterized in that: a wavelength tunable laser, a polarization controller, a double-arm Mach-Zehnder modulator, a narrowband phase-shifted fiber grating and a high speed photoelectric detector are connected in order by fibers; and radio frequency input ports of the high speed photoelectric detector, a microwave high pass filter, a microwave amplifier, a microwave phase shifter, a microwave coupler, a microwave 3dB quadrature coupler and the double-arm Mach-Zehnder modulator are connected in order by microwave coaxial lines. Besides, a closed opto-electronic oscillation loop is formed by the double-arm Mach-Zehnder modulator, the narrowband phase-shifted fiber grating, the high speed photoelectric detector, the microwave high pass filter, the microwave amplifier, the microwave phase shifter, the microwave coupler, and the microwave 3dB quadrature coupler; and a high quality microwave signal with a tunable frequency and a tunable broadband is generated at another output port of the microwave coupler by adjustinga wavelength of the wavelength tunable laser. According to the invention, the opto-electronic oscillator has advantages of compact structure, fast frequency adjusting speed, and wide tunable frequency domain and the like.

The invention discloses a highly-stable single-mode microwave optoelectronic oscillator. A modulator B (5) is arranged in an optoelectronic oscillator (OEO) loop and driven by a highly-stable microwave source (12), output modes of the oscillator can be chosen through a modulation mode locking process, and edge mode noise is inhibited through gain competition between the modes. Simultaneously a phase-locked loop theory is used for comparing output signals of the OEO with output signals of the highly-stable microwave source (12), a phase (or cavity length of the OEC) for controlling the output signals of the OEO is fed back, and finally stable single-mode OEO output is obtained. The highly-stable single-mode microwave optoelectronic oscillator can achieve frequency stabilization phase lock and single-mode operation of the OEO simultaneously, is simple in structure and low in cost, and has practical value.

There is provided a photoconductive element capable of generating and detecting broadband electromagnetic waves such as terahertz waves at a comparatively high efficiency by decreasing or avoiding the absorption of electromagnetic waves into a substrate. A photoconductive element 1 includes a photoconductive film 5 exhibiting conductivity by the radiation of light, a substrate 6 holding the photoconductive film and a thin film sandwiched between the photoconductive film 5 and the substrate 6, the thin film being different in composition from the photoconductive film 5 and the substrate 6. The photoconductive film 5 is provided with an antenna 7 having a gap portion 2 and an electrode 4 electrically connectable to the antenna 7. At least a part of the photoconductive film where the gap portion 2 of the antenna 7 is located is single crystal. The substrate 6 has an opening portion 3 at a part corresponding to a part of the photoconductive film 5 where the gap portion 2 of the antenna 7 is located.

The present invention improves the efficiency of conversion from a non-radiation two-dimensional electron plasmon wave into a radiation electromagnetic wave, and realizes a wide-band characteristic. A terahertz electromagnetic wave radiation element of the present invention comprises a semiinsulating semiconductor bulk layer, a two-dimensional electron layer formed directly above the semiconductor bulk layer by a semiconductor heterojunction structure, source and drain electrodes electrically connected to two opposed sides of the two-dimensional electron layer, a double gate electrode grating which is provided in the vicinity of and parallel to the upper surface of the two-dimensional electron layer and for which two different dc bias potentials can be alternately set, and a transparent metal mirror provided in contact with the lower surface of the semiconductor bulk layer, formed into a film shape, functioning as a reflecting mirror in the terahertz band, and being transparent in the light wave band. Two light waves are caused to enter from the lower surface of the transparent metal mirror, and two different dc bias potentials are alternately applied to the double gate electrode grating so as to periodically modulate the electron density of the two-dimensional electron layer in accordance with the configuration of the double gate electrode grating.

The present invention provides an optical semiconductor device including a semiconductor thin film (4) having photoconductivity and a pair of electrodes (5) and (10) for applying an electric field to an inside of the semiconductor thin film (4) in a direction approximately vertical to a surface of the semiconductor thin film (4), wherein the semiconductor thin film (4) generates an electromagnetic wave when light is applied to a region thereof to which the electric field is applied. The electrodes are provided to a front surface and a back surface of the semiconductor thin film (4) with the semiconductor thin film interposed therebetween.

The invention provides a broadband tuning teraHertz wave generator based on modulator frequency shift and cyclic frequency shift, comprising a laser, a circulator, a light beam splitter, a cyclic frequency shift link based on the modulator frequency shift, a light beam synthesizer, a photoisolator and a photoelectric transducer with a teraHertz radiating antenna, wherein light output by the laser passes through the circulator and then is divided into a first path and a second path by the light beam splitter; the light in the first path belongs to reference light; the light in the second path is input into the cyclic frequency shift link to generate cyclic frequency shift light; the reference light and the cyclic frequency shift light are superposed in the light beam synthesizer to generate beat frequency light in the range of teraHertz frequency; and the beat frequency light passes through the photoisolator and then is received by the photoelectric transducer with the teraHertz radiating antenna, and the photoelectric transducer with the teraHertz radiating antenna gives off coherent teraHertz waves. The generator provided by the invention has the advantages that the volume is small, and fewer optical elements are used, thus being easy to integrate, the tuning range is wide, the tuning efficiency is high and the generating efficiency of the teraHertz waves is high.

A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. An antenna connected to the Schottky diode receives a terahertz signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

The invention relates to a method capable of adjusting the polarization and the intensity of a terahertz wave rapidly and continuously. According to the method, a focusing lens is arranged at the outlet of a femto-second laser; incident laser passes through the focusing lens and a doubling frequency crystal in sequence to generate frequency doubled light; the frequency doubled light and remaining fundamental frequency laser pass through a uniaxial birefringent crystal wafer together; according to the principle that the refractive indexes of the fundamental frequency laser and the frequency doubled light in a uniaxial birefringent crystal are different, the optical path difference, namely the time delay, between the fundamental frequency laser and the frequency doubled light can be changed by adjusting the thickness of the uniaxial birefringent crystal wafer and the spatial included angle between a glass piece and an incident light beam, so that the relative phase between the fundamental frequency laser and the frequency doubled light is changed; and therefore, the polarization and the intensity of the finally generated terahertz wave are adjusted. Finally, the generated terahertz wave enters a terahertz wave detection system after being filtered by a high-resistance silicon wafer. By the method, the polarization and the intensity of the terahertz wave can be adjusted rapidly and continuously; and the operation is simple, rapid and effective.

The invention discloses an all-optical microwave multiplier based on the non-linear polarization rotation effect. The all-optical microwave multiplier comprises a first continuous photo-semiconductor laser device, a first polarization controller, an electro-optical intensity modulator, a microwave signal source, a second continuous photo-semiconductor laser device, a second polarization controller, an optical amplifier, a third polarization controller, an optical coupler, a non-linear photoelectric device, a band-pass filter, a polarization beam splitter, an optical circulator, an optical fiber grating, a first photoelectric detector and a second photoelectric detector, which are connected in series. According to the all-optical microwave multiplier based on the non-linear polarization rotation effect, the technical problems that the traditional photo-generated microwave and up-conversion scheme is difficult to get rid of the dependence on a high-frequency external microwave source, the wavelength of an optical carrier of a generated signal is limited, the conversion efficiency is low and even a high-frequency microwave signal is difficultly generated and the like, can be solved.

A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. A terahertz signal can be received by an antenna connected to the mixer, an end facet or sidewall of the laser, or through a separate active section that can amplify the incident signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

The invention provides a cascaded microwave photonic filter-based photoelectric oscillator with a tunable broadband. The cascaded microwave photonic filter-based photoelectric oscillator comprises a first laser, a first polarization controller, a phase modulator, a first MPBF unit, a second MPBF unit, a first variable optical attenuator, a photodiode, an electric amplifier and an electric power divider which are sequentially connected, wherein a first output end of the electric power divider is used for outputting a generated microwave signal; a second output end of the electric power divideris connected with a radio frequency port of the phase modulator; when the photoelectric oscillator works, a phase modulation signal enters the first MPBF unit and then first mode selection is carriedout by using a single bandpass microwave photonic filter with the tunable broadband, thereby selecting an oscillation starting frequency of the OEO, and the phase modulation signal passes through thesecond MPBF unit and then auxiliary mode selection through an ultra-narrow bandwidth MPBF is achieved, thereby achieving single-mode oscillation starting of the OEO. A cascaded microwave photonic bandpass filter is utilized and combined with the OEO, so that single-mode oscillation starting of the OEO is achieved through multiple mode selection; and the broadband tenability of the OEO can be achieved through adjusting the central wavelength of the first MPBF unit.

A method and device for generating terahertz radiation comprising a polar crystal material layer operative to emit terahertz radiation; the polar crystal material layer comprising a plurality of stacking faults; the stacking faults lying substantially perpendicular to the polar axis and forming boundaries at which the internal electric polarization terminates leading to charges accumulating at the boundaries, and creation of internal electric fields oriented along the polar axis; a pulsed radiation source for creating photogenerated carriers in the polar crystal material; whereby the photogenerated carriers accelerate in the internal electric fields associated with the termination of the internal electric polarization by the stacking faults to thereby generate terahertz radiation.

A device capable of generating multi-bandwidth high-frequency tunable microwave signals comprises a laser device (100), a coupler (101), a frequency shift unit (102), an optical fiber amplifier (107), a third coupler (115), a photoelectric detector (116) and a Brillouin ring cavity laser unit (108). Laser light generated by the laser device is split to two beams by the coupler, one beam of laser light serves as pumping light to enter the frequency shift unit, the Brillouin ring cavity laser unit comprises a second circulator, a polarization controller, a second coupler, an optical fiber unit and a temperature or stress controller unit, light outputted by the optical fiber amplifier is switched into a first port of the second circulator, an optical isolator is added in the transmission direction of Brillouin scattering signals, the Brillouin scattering signals are outputted from a split arm of the second coupler, and the outputted Brillouin scattering signals and local oscillating light outputted by the coupler are coupled on the third coupler and are converted into the microwave signals for output by the aid of the photoelectric detector.