Showing papers on "Signal beam published in 2019"

Detection method for the complex amplitude of a signal beam with intensity and phase modulation using the transport of intensity equation for holographic data storage

Abstract: Holographic data storage (HDS), in which both the amplitude and the phase of a signal beam are modulated, has been extensively studied with the goal of increasing its storage capacity. To detect such modulation during data retrieval, it is necessary to acquire the complex amplitude of the signal beam. In this study, we focus on the transport of intensity equation (TIE) method, which allows us to detect the phase distribution of the light wave quantitatively without using interferometry, contributing to miniaturization of the optical system and improvement of the vibration tolerance of HDS. We discuss the conditions of the modulation phase distribution of the signal beam required for accurate phase detection and propose a method to estimate and eliminate the noise that frequently appears in the phase distribution detected by the TIE method.

Holographic interference in atomic photoionization from a semiclassical standpoint

Abstract: A theoretical study of the interference pattern imprinted on the doubly differential momentum distribution of the photoelectron due to atomic ionization induced by a short laser pulse is developed from a semiclassical standpoint. We use the semiclassical two-step model of Shvetsov-Shilovski et al. [Phys. Rev. A 94, 013415 (2016)] to elucidate the nature of the holographic structure. Three different types of trajectories are characterized during the ionization process by a single-cycle pulse with three different types of interferences. We show that the holographic interference arises from the ionization yield only during the first half cycle of the pulse, whereas the coherent superposition of electron trajectories during the first half cycle and the second half cycle gives rise to two other kinds of intracycle interference. Although the picture of interference of a reference beam and a signal beam is adequate, we show that our results for the formation of the holographic pattern agree with the glory rescattering theory of Xia et al. [Phys. Rev. Lett. 121, 143201 (2018)]. We probe the two-step semiclassical model by comparing it to the numerical results of the time-dependent Schr\"odinger equation.

Highly efficient continuous-wave mid-infrared generation based on intracavity difference frequency mixing

Abstract: We report on a new scheme for efficient continuous-wave(CW) mid-infrared generation using difference frequency generation(DFG) inside a periodically poled lithium niobate(PPLN)-based optical parametric oscillator(OPO). The pump sources were two CW fiber lasers fixed at 1018 nm and 1080 nm. One worked as the assisted laser to build parametric oscillation and generate an oscillating signal beam while the other worked at low power( 3 W) to induce DFG between it and the signal beam. The PPLN temperature was appropriately adjusted to enable OPO and DFG to synchronously meet phase-matching conditions. Finally, both low-power 1018 nm and 1080 nm pump beams were successfully converted to 3.1 μm and 3.7 μm idler beams, respectively. The conversion efficiencies of the 1018 nm and 1080 nm pumped DFG reached 20% and 15%, respectively, while their slope efficiencies reached 19.6% and 15%.All these data were comparable to the OPOs pumped by themselves and never realized before in traditional CW DFG schemes. The results reveal that high-efficiency frequency down-conversion can be achieved with a low-power nearinfrared pump source.

Tunable ultraviolet vortex source based on a continuous-wave optical parametric oscillator.

Abstract: We report a continuous-wave (cw) optical parametric oscillator (OPO) generating optical vortices tunable in the ultraviolet (UV). Based on MgO:sPPLT as the nonlinear crystal, the singly resonant OPO is pumped by a cw vortex beam in the green, and deploying intracavity sum-frequency generation (SFG) between the undepleted pump and the Gaussian resonant signal in the crystal of BiB3O6, it can generate optical vortices of order, l u v =1 and 2, tunable across 332–344 nm in the UV with a maximum power of 12 mW. Due to conservation of orbital angular momentum in the parametric process, the OPO also produces a non-resonant idler output beam in a vortex spatial profile of order li=1 and 2, identical to the pump vortex, with the signal beam in Gaussian distribution. The idler vortex is tunable across 1172–1338 nm with maximum output power of 1.3 W.

93-GHz Signal Beam Steering with True Time Delayed Integrated Optical Beamforming Network

Abstract: A 93-GHz beam steering experiment based on a 1 × 4 phased array antenna was demonstrated, achieving beam steering angles of −51°, ±34°, ±17° and 0°. An integrated optical beamforming network chip with true time delays was employed.

Low-probability-of-intercept transmitted signal design method based on FDA-OFDM

Abstract: The invention discloses a low-probability-of-intercept transmitted signal waveform design method based on FDA-OFDM. The invention solves the technical problem that a frequency diversity array transmitted signal is easy to intercept and interfere. The low-probability-of-intercept transmitted signal waveform design method comprises an implementation method of: constructing an array model of a frequency diversity array; designing an orthogonal transmitted signal; constructing an array oriented matrix A; defining a weighting moderate matrix W; and by the array oriented matrix A and the weighting moderate matrix W together, obtaining a frequency diversity array beam energy diagram so as to complete low-probability-of-intercept transmitted signal waveform design based on FDA-OFDM. According to the invention, the transmitted signal adopts orthogonal waveform design; each array element uses two orthogonal subcarriers; a transmitted signal beam pattern is changed from conventionality, complexity is improved, and the transmitted signal beam pattern is a result of overlaying two transmitted signals at an assumed target position. According to the invention, the probability of intercepting andidentifying the transmitted signals is reduced, interference resistance is promoted, and the low-probability-of-intercept transmitted signal waveform design method is beneficial for implementing low-probability-of-intercept performance of the signals. The low-probability-of-intercept transmitted signal waveform design method can be applied to a frequency diversity array MIMO radar, inhibition on distance correlation interference and spuriousness and low-probability-of-intercept electronic detection.

High-power femtosecond cylindrical vector beam optical parametric oscillator.

Abstract: We report on high-power femtosecond cylindrical vector beam (CVB) generation from a Gaussian-pumped optical parametric oscillator (OPO). By introducing a half waveplate and a vortex half-wave plate of m = 1 to realize intracavity polarization modulation to the resonant Gaussian signal, the OPO could deliver broadband signal beam in CVB profile, i.e., radially and azimuthally polarized beam profile. The central wavelength of the generated CVB signals can be tuned continuously from 1405 to 1601 nm, while the corresponding pulse durations are all around 150 fs. A maximum average output power of 614 mW at 1505 nm is obtained. Moreover, our OPO cavity design can be extended to generate high order CVB by simply changing the vortex half-wave plate with different orders. Such a high-power CVB OPO configuration has the advantages of flexible control and wide tuning range, making it a practical tool for applications in super-resolution imaging, optical communication and quantum correlations.

Validation of pre-compensation under point-ahead-angle in a 1 km free-space propagation experiment.

Abstract: Adaptive optical pre-compensation is seen as crucial for free-space laser communication in order to overcome the influence of atmospheric turbulence, particularly with respect to Earth-to-GEO feederlinks. This paper presents an experimental investigation into adaptive optical pre-compensation under large point-ahead-angles. We detail the design and realization of a free-space laser communication experiment over a 1.0 km horizontal path using a divergent beacon beam and a focussed signal beam, propagating in opposite directions. We describe the design and development of our experimental setup and measurement campaign using real turbulence. The median isoplanatic angle was calculated to be 0.16 mrad, while an increase in the received optical power through pre-compensation could be demonstrated for point-ahead-angles in the range of 0.13 mrad to 0.27 mrad.

Low Threshold, Dual-Wavelength, Mid-Infrared Optical Parametric Oscillator

Abstract: In this letter, we demonstrated a dual-wavelength (DW) mid-infrared optical parametric oscillator (OPO) that was pumped by two independent fiber lasers fixed at 1018 nm and 1080 nm, and realized phase-matched signal beam coupling by tuning grating period of PPLN. Based on signal beam coupling, two interesting phenomena were observed for the first time. One is that the OPO threshold for 1018 nm and 1080 nm pump beams could be drastically lowered from 15.4 W to 266 mW and from 13.5 W to 1.38 W separately. The other is that the total idler power obtained when the OPO was simultaneously pumped by two fiber lasers was higher than sum of idler power obtained when the OPO was independently pumped by two fiber lasers, revealing obvious parametric gain enhancement. It also indicated that the two independent OPO processes became coherent when two signal beams were coupled. The results exhibit great potential in practical applications such as frequency down-conversion of some special near-infrared laser sources such as pulsed single-frequency sources, spectrum high-speed swept sources, and ultra-short pulse sources with low duty cycle.

Transferring of Continuous Variable Squeezed States in 20 km Fiber

Abstract: Transferring of a real quantum state in a long-distance channel is an important task in the development of quantum information networks. For greatly suppressing the relative phase fluctuations between the signal beam and the corresponding local oscillator beam, the usual method is to transfer them with time-division and polarization-division multiplexing through the same fiber. But the nonclassical states of light are very sensitive to the channel loss and extra noise, this multiplexing method must bring the extra loss to the quantum state, which may result in the vanishing of its quantum property. Here, we propose and realize a suitable time multiplexing method for the transferring and measurement of nonclassical states. Only the local oscillator beam is chopped into a sequence of light pulses and transmitted through fiber with continuous orthogonal-polarized signal beam. Finally, when the local oscillator pulses are properly time delayed compared to the signal beam, the quantum state can be measured in the time sequences without the influence of extra noise in the fiber. Our work provides a feasible scheme to transfer a quantum state in relative long distance and construct a practical quantum information network in metropolitan region.

Suppression of inter-pixel cross talk and reduction of recording spot size for high-density holographic memory

Abstract: In the previous study, we evaluated the effectiveness of an orthogonal polarizer array to suppress the inter-pixel cross talk with respect to the page data recording in holographic memory (Nobukawa et al. in Opt Express 25:22425, 2017). The reconstruction quality was improved by the use of the orthogonal polarizer array applied for the signal beam, based on the reduction of inter-pixel cross talk. In the present study, we also employed a similar polarizer array for the detection of a reconstructed image. Simultaneously, some phase shift masks and various apertures restricting the recording spot were also applied for the holographic recording. As a result, we found that the areal density and reconstruction quality were improved significantly based on the suppression of inter-pixel cross talk and reduction of recording spot size. These findings can be used for the realization of practical high-density holographic memory.

Atmospheric turbulence distortion compensation system and method in orbital angular momentum light transmission

Abstract: The invention discloses an atmospheric turbulence distortion compensation system and method in orbital angular momentum light transmission, and relates to the orbital angular momentum optical communication technology. The system is characterized in that a polarization beam splitter (1), a beam splitter (2), a charge coupling camera (3) and an FPGA (Field Programmable Gate Array) board (4) are sequentially communicated to realize mode identification of a signal beam; wherein the FPGA board (4) is communicated with the spatial light modulator (5), the beam splitter (2) is communicated with the 90-degree optical mixer (6), and the polarization beam splitter (1), the spatial light modulator (5), the 90-degree optical mixer (6) and the photoelectric detector (7) are sequentially communicated tocomplete turbulence compensation of a signal beam. Compared with the prior art, the invention has the following advantages and positive effects: (1) not only is the structure of the compensation system simplified, but also the operation difficulty of application in actual communication is reduced; and (2) the mode identification of the multimode multiplexing OAM light beam is realized, and meanwhile, the signal light beam compensation is completed.

Determination of a preferred beam in a cellular communication network employing signal beam-forming

Abstract: An arrangement for determination of a preferred beam is disclosed. The arrangement is for a wireless communication device adapted to communicate with a network node of a cellular communication network. The network node is adapted to support a plurality of beams of a signal beam-forming scheme and to communicate with the wireless communication device using at least one beam of the plurality of beams. The arrangement comprises a controller adapted to cause reception, from the network node, of a message indicative of a beam power setting of the plurality of beams, wherein the beam power setting comprises a power offset being applied to at least one beam of the plurality of beams. The power offset is relative to a nominal power setting of the plurality of beams and the message comprises a value of the power offset. The controller is further adapted to cause measurements being performed on measurement signals transmitted by the network node and determination of the preferred beam based on the measurements and the beam power setting. It is also adapted to cause transmission, to the network node, of a report indicative of the preferred beam.

Apparatus for Transmitting Audio Signal

Abstract: The present invention relates to a wireless apparatus for transmitting an audio signal, including: an audio signal transmission unit converting the audio signal which is output from an audio device to an invisible light signal beam, and transmitting the audio signal; a transmission device including at least one array signal transmission unit which transmits a visible light laser signal beam; a repeater device changing a path of the invisible light signal beam or a path of the visible light laser signal beam transmitted from the transmission device; and a receiving device outputting the audio signal to a speaker by converting the invisible light signal transferred from the repeater device, and having at least one array induction mark in a predetermined area

Weak light image stochastic resonance reconstruction method and device based on cross modulation instability

Abstract: The invention relates to a weak light image stochastic resonance reconstruction method and device based on cross modulation instability, which solves the technical problems of discrete intensity modulation and image detail loss in the existing single path stochastic resonance reconstruction method. The method and the device combine the scattered image signal beam and the coherence-controllable noise beam to propagate in a nonlinear crystal, and generate mode coupling and phase modulation by adding a coherence-controllable noise beam. The additional noise beam changes the spatial frequency composition of the scattered signal beam and provides enough energy for nonlinear coupling so that the intensity distribution of the reconstructed enhanced weak-light image is uniform and more high-frequency details are presented.

Beam-steerable antenna devices, systems, and methods

Abstract: Devices, systems, and methods for a compact beam-steerable antenna array for centimeter-wave and millimeter-wave mobile terminals, the antenna array having a steerable beam without phase shifters. In some embodiments, an antenna array includes an active antenna element and at least one parasitic element spaced apart from the active antenna element. An impedance between each of the at least one parasitic element and a ground element is tunable to steer a signal beam at the active antenna element in a desired direction.

Nanosecond pulse laser light source structure with tunable pulse width and power

Abstract: The invention discloses a nanosecond pulse laser light source structure with tunable pulse width and power. The nanosecond pulse laser light source structure comprises a nanosecond seed light source system which is used for synchronously triggering and splitting a main laser beam with fixed power and pulse width so as to obtain a plurality of split-beam pulse lasers; a plurality of amplification systems which are respectively arranged on split beam output links and are used for carrying out gain amplification on the split beam laser; a nanosecond delay system which is used for carrying out delay adjustment on the output of each amplified split-beam laser signal; and a signal beam combiner which is used for carrying out beam combination processing on the amplified and delayed split beam laser signals. According to the nanosecond pulse laser light source structure with tunable pulse width and power provided by the invention, a mode of adjusting the power and mutual time delay of each beam splitting laser pulse is adopted to realize tunable nanosecond pulse laser output with the average power being 200-5000W and pulse width being 30-2000ns, so that the universality of the nanosecond pulse laser light source in the fields of industry and national defense is improved.

Coherent optical receiver module and method for manufacturing the same

Abstract: A coherent optical receiver module is disclosed. The module includes a housing, an optical fiber group, a first optical element, and a second optical element. The housing stores a first optical component disposed on an optical path of a local beam and a second optical component disposed on an optical path of a signal beam. The optical fiber group includes a first optical fiber optically coupled to the first optical component and a second optical fiber optically coupled to the second optical component. The first optical element has a first lens disposed on the optical path of the local beam, and transmits the signal beam and the local beam. The second optical element has a second lens disposed on the optical path of the signal beam, and transmits the signal beam and the local beam. The first optical element and the second optical element are placed side by side between the optical fiber group and one end surface of the housing.

Fiber optical parametric chirped-pulse amplification (FOPCPA)

Abstract: The technology described in this document can be used to implement an optical device including a seed pump laser to produce pump seed laser pulses at a pump wavelength, a pulse stretcher operable to stretch a pulse duration of the pump seed laser pulses to produce stretched pump seed laser pulses, a pump fiber amplifier including one or more fiber gain media to receive the seed pump laser pulses to produce a pump laser beam of pump laser pulses, a signal laser to produce a signal laser beam at a signal wavelength different from the pump wavelength, an optical module coupled to combine the pump laser beam and the signal laser beam, and a fiber optical parametric amplifier (OPA) to cause a nonlinear parametric interaction in the nonlinear fiber medium to produce an output signal beam, an output idler laser beam at an idler wavelength, and an output pump beam.

Filter assembly for ultrasound image signal, beam focusing apparatus using same, and beam focusing method thereof

Abstract: A beam focusing method according to an embodiment of the present invention comprises the steps of: compensating for a coarse delay by fetching data from a memory, in which received ultrasound signal data is sequentially stored, with reference to a coarse delay address; determining data, which has been coarse-delayed in the process of being fetched from the memory, as an input group according to a variable decimation ratio; selecting, by a shift register, a filter coefficient group having a phase corresponding to a fine delay error of the input group; compensating for a fine delay time by supplying the selected filter coefficient group and the input group to a partial-sum computational-body including a multiplier-accumulator (MAC); and calculating a beam focusing result by adding output values of all channels provided with partial-sum computational-bodies.

Coherent receiver module

Abstract: The receiver including a package, first and second optical fibers, a capillary, and an array lens is disclosed. The first fiber has a first edge coupling to a MMI device by propagating a signal beam. The second fiber has a second edge coupling to the MMI device by propagating a local beam. The array lens has first and second lenses. The first lens converts the signal beam into a collimating beam, and the second lens converts the local beam into a collimating beam. The capillary has an edge opposite to the array lens, and the edge has a first region including the first edge and a second region including the second edge. The first edge is slanted to a first axis, and the second edge is slanted to a second axis, and a direction of the first edge and a direction of the second edge are different each other.

Improved frequency conversion system

Abstract: The invention concerns a frequency conversion system (10) suitable for generating at least one converted beam (Fc) having a converted frequency (vc) from at least one signal beam (Fs) having a signal frequency (vs), by using a plurality of n elementary pump beams Fp,i indexed i, i varying from 1 to n, n being greater than or equal to 2, having a pump frequency (vp), the system comprising: - a crystal (CR) comprising a material (M) for which the sign of the second order non-linear coefficient (χ(2)) is periodically inverted along an axis Z - an optical device (OD) configured to generate said plurality of n elementary pump beams from an initial pump beam (Fpini), an elementary pump beam Fp,i+1 of index i+1 being generated by redirecting the elementary pump beam Fp,i of index i toward the crystal after it has crossed the crystal.

Optical parametric laser amplifier preparation method and optical parametric laser amplifier

Abstract: Disclosed are an optical parametric laser amplifier preparation method and an optical parametric laser amplifier, comprising: determining a mapping relationship between a first non-collinear angle and a second non-collinear angle by using a preset non-collinear phase matching formula, wherein the first non-collinear angle is the angle between the transmission directions of a pump beam and a signal beam, and the second non-collinear angle is the angle between the transmission directions of the pump beam and an idler beam; determining a first target non-collinear angle and a second target non-collinear angle based on a preset temperature partial derivative formula and the mapping relationship; and preparing an optical parametric laser amplifier based on the first target non-collinear angle and the second target non-collinear angle. The performance of the optical parametric laser amplifier prepared by the above method is not greatly affected by temperature variation. When the temperature of the non-linear crystal changes and deviates from the original phase matching temperature, the second target non-collinear angle is automatically adjusted to perform phase compensation, such that the phase matching of the optical parametric laser amplifier is not lost, thereby improving the energy conversion efficiency of an optical parametric laser amplifier operating with a high mean power.

Optical parametric chirped-pulse amplification (opcpa)

Abstract: The technology described in this document can be used to implement an optical device including a seed pump laser to produce pump seed laser pulses at a pump wavelength, a pulse stretcher operable to stretch a pulse duration of the pump seed laser pulses to produce stretched pump seed laser pulses, a pump fiber amplifier including one or more fiber gain media to receive the seed pump laser pulses to produce a pump laser beam of pump laser pulses, a signal laser to produce a signal laser beam at a signal wavelength different from the pump wavelength, an optical module coupled to combine the pump laser beam and the signal laser beam, and a fiber optical parametric amplifier (OPA) to cause a nonlinear parametric interaction in the nonlinear fiber medium to produce an output signal beam, an output idler laser beam at an idler wavelength, and an output pump beam.

Wireless devices having spirally-distributed beam pointing angles

Abstract: An electronic device may be provided with a phased antenna array, control circuitry, and a codebook. The control circuitry may control the phased antenna array to form a signal beam at a beam steering angle selected from a set of beam steering angles identified by the codebook. The set of beam steering angles may be evenly distributed along a two-dimensional or three-dimensional spiral path. The control circuitry may control the phased antenna array to sweep over the set of beam steering angles until external wireless equipment is found. Distributing the set of beam steering angles in this way may minimize the size of the codebook while allowing the phased antenna array to cover as much of its field of view as possible with satisfactory gain.

Fiber bragg grating strain measuring device with adjustable measuring range

Abstract: The invention discloses a fiber bragg grating strain measuring device with an adjustable measuring range. The structure comprises a broadband light source used for generating certain spectral width output, an optical fiber coupler used for optical signal beam splitting and coupling, a strain measuring module used for strain measurement, a photoelectric detector used for converting an optical signal into an electric signal and a signal processing module. The structure is simple, a strain measuring range can be conveniently adjusted, and a large strain exceeding a sensor measuring range is converted into the sensor strain measurement range so as to realize nonreplaced strain measurement of a sensor. The structure is clear, stability is high and manufacturing is simple.

Device and method for detecting verticality of diffraction grating

Abstract: An embodiment of the present invention provides a device and method for detecting the verticality of a diffraction grating. The device includes a laser unit, a circulator, a grating to be detected, abeam guiding unit, and a detecting unit. First signal light emitted by the laser unit is irradiated on the grating to be detected by the circulator, the grating to be detected splits the first signallight into a second signal beam, and the second signal beam is emitted. The beam guiding unit is used for shaping and reflecting the second signal beam such that the second signal beam can return to the grating to be detected along an original path. The grating to be detected is also used for combining the second signal beam into third signal light, the third signal light is emitted into the detection unit through the circulator, and the detection unit is used for detecting the wavelength related loss of the third signal light. The wavelength related loss is used for obtaining the verticalityof the grating to be detected and/or judging whether the verticality of the grating to be detected is qualified. According to the device and the method provided by the embodiment of the invention, thenon-contact detection of the verticality of the diffraction grating is achieved, and the probability of the damage to the diffraction grating is little.

Optical multiplexer/demultiplexer, optical subassembly, and optical module

Abstract: An optical multiplexer/demultiplexer may include some beam splitters on the first surface, a first reflector on the first surface and between the beam splitters, and a second reflector on the second surface. Light propagates between the first surface and the second surface. The light transmission body has some first input/output sections on the first surface for inputting or outputting the respective signal beams. The light transmission body has a second input/output section on the second surface for inputting or outputting the multiplexed signal beam. Each of the beam splitters is placed at a corresponding one of the first input/output sections to pass a corresponding one of the signal beams. The first reflector stays away from any one of the first input/output sections.