Showing papers on "Signal beam published in 2018"

Mid-infrared ZGP OPO with divergence compensation and high beam quality.

Abstract: Divergence compensation, optimization of the optical-to-optical efficiency, and high beam quality of signal and idler beams of a high-energy mid-infrared ZnGeP2 (ZGP) optical parametric oscillator (OPO) have been demonstrated by use of a Galilean telescope inside the nonplanar fractional-image-rotation enhancement (FIRE) ring resonator. With a small variation of the distance between the lenses of the telescope, the divergences of signal and idler beams could be adjusted. Up to 36 mJ of mid-infrared pulse energy in the 3-5 µm wavelength range is obtained with 92 mJ of pump energy on crystal. The beam quality factors M2 are < 1.5 for the resonant signal beam and the non-resonant idler beam, respectively. Actually, this is an improvement of the beam quality by a factor 3 for the signal and ~2.7 for the idler beam compared without using a telescope inside the FIRE ring resonator.

Classical imaging with undetected light

Abstract: We obtained the phase and intensity images of an object by detecting classical light which never interacted with it. With a double passage of a pump and a signal laser beams through a nonlinear crystal, we observe interference between the two idler beams produced by stimulated parametric down conversion. The object is placed in the amplified signal beam after its first passage through the crystal and the image is observed in the interference of the generated idler beams. High contrast images can be obtained even for objects with small transmittance coefficient due to the geometry of the interferometer and to the stimulated parametric emission. Like its quantum counterpart, this three-color imaging concept can be useful when the object must be probed with light at a wavelength for which detectors are not available.

Beam selection and refinement during a random access channel (RACH) procedure

Abstract: Aspects of the present disclosure relate to wireless communications and, more particularly, to beam refinement during a RACH procedure. A NB may receive a message via a first beam from a UE as part of a RACH procedure and may transmit at least one signal for beam refinement during the RACH procedure. A UE may transmit, to a NB, a message via a first beam as part of a RACH procedure and may receive, from the NB, at least one signal for beam refinement during the RACH procedure. Any directional signal beam may be used for beam refinement as described herein.

High-power, high repetition rate, tunable, ultrafast vortex beam in the near-infrared

Abstract: We report on experimental demonstration of high power, ultrafast, high repetition rate (RR) vortex beam source tunable in the near-IR wavelength range. Based on single-pass optical parametric generation of Yb-fiber laser of vortex order l p = 1 in a 50 mm long MgO doped periodically poled LiNbO3 crystal, the source produces signal beam in vortex profile of order l s = 1 across 1433–1553 nm. Additionally, the source produces broadband idler radiation tunable across 3379–4132 nm in the Gaussian beam profile. We observed that the vortex profile of the pump beam is always transferred to the signal beam due to the highest overlapping integral among the interacting beams and the idler maintains a Gaussian spatial profile owing to the conservation of orbital angular momentum in optical parametric processes. For a pump power of 4.72 W, the signal and idler beams have a maximum power of 1.7 W at 1509 nm and 0.48 W at 3625 nm respectively. The signal vortex beam has output pulses of width ~637 fs at a RR of 78 MHz. The signal (idler) has a spectral width of 4.3 nm (129.5 nm) and a passive peak-to-peak power fluctuation better than 3% (1.1%) over 30 min, respectively.

Tunable Dual-Wavelength, Continuous-Wave, Mid-Infrared Generation Using Intracavity Difference Frequency Mixing in PPLN-Based Optical Parametric Oscillator

Abstract: We report on a widely tunable, dual-wavelength, continuous-wave, mid-infrared optical parametric oscillator (OPO), pumped by a dual-wavelength fiber source that was realized by combining two fiber lasers in series. The OPO was designed as a four-mirror singly resonant cavity, in which a periodically poled lithium niobate (PPLN) crystal was used as nonlinear crystal. Two idler emissions with different wavelengths were observed, one being basically fixed at 3140 nm and the other being tunable from 3227 to 3413 nm. Under the maximum pump power, the total idler power was over 6 W and the corresponding pump-to-idler slope efficiency reached 11.4%. The generated signal beam had just one central wavelength around 1600 nm. Through theoretical analysis and experimental verification, it was analyzed that two nonlinear processes, OPO and intracavity difference frequency generation (DFG), simultaneously occurred in the resonant cavity. The experimental phenomena revealed large widened DFG gain spectrum, which was in absolute contrast to simulation results based on classical DFG theory. It indicated great potential in practical application such ultra-wide nonlinear frequency conversion.

Investigation of residual amplitude modulation in squeezed state generation system.

Abstract: We present an analysis on how the optical parametric oscillator (OPO) detuning and the relative phase drift deteriorate the stability of the squeezed states, including the output power and the squeezed degree, and investigate the influence of RAM on the cavity detuning and the relative phase drift under different cases. Subsequently, the RAM is experimentally measured. In term of the measurement results, we perform a comparative study about RAM’s influence on the cavity and phase locking in two cases. As a result, with the error signal extracted from the transmission of the OPO, the output power stability of the squeezed light is greatly improved. With the phase modulation imposed on the signal beam, the long-term stability of the squeezed degree is significantly enhanced.

An Ultra Small Optical Switch Design Based on Directional Coupler in Two-dimensional Photonic Crystals

Abstract: We theoretically investigate an ultra small structure with directional coupler (DC) in a two dimensional (2D) photonic crystal (PhC)for realizing the switching phenomenon. In this design, triangular lattice of air holes in dielectric matrix is utilized. The DC is formed by creating two straight line defect waveguides, separated by single row of air holes. We showed that by adjusting the size of the air holes between both the two waveguides, the input signal beam can be switched to a different output ports with a response timeless than 2ps. Difference Time Domain (FDTD) technique is used to simulate the power-time switching curves. The advantages of this method are high stability and accuracy in computations. The total size of the proposed switch is 31.85μm2 which is highly suitable for Photonic Integrated Circuits (PICs).

Test equipment and testing methods based on harmonic beamforming

Abstract: Apparatus and methods for radio frequency emissions testing based on harmonic beamforming are provided herein. In certain configurations, a method of emissions testing of cellular communication assemblies for emissions compliance is provided. The method includes transmitting a signal beam using an antenna array of a respective cellular communication assembly after manufacture thereof, the signal beam including a fundamental lobe and one or more harmonic lobes. The method further includes determining one or more testing locations of the signal beam based on detecting a direction of the fundamental lobe using test equipment, the testing locations corresponding to locations associated with the harmonic lobes. The method further includes evaluating a level of harmonic emissions at each of the one or more testing locations using the test equipment to establish whether or not the respective cellular communication assembly complies with emissions testing.

Analysis of interference fringes based on three circularly polarized beams targeted for birefringence distribution measurements.

Abstract: As a potential means of measuring birefringence distribution, we analyzed the interference fringes based on three circularly polarized beams: a right-handed signal beam, a left-handed reference beam, and a right-handed reference beam. All beams were crossed at the same angle on the interfering plane, creating a two-dimensional interference fringe with three grating vectors. We proposed that by analyzing the interference fringes, we can measure the anisotropic phase shift in the signal beam. The obtained features of the anisotropic phase shift can be extended to the measurement of two-dimensional birefringence distributions without rotational manipulations of the objectives or polarizers. The fringes were generated by monolithic gratings, which can generate three-beam interfering fields precisely and easily. Finally, we confirmed the feasibility of a birefringence measurement system without any rotational manipulations of optics.

Experimental implementation of multiplexing/demultiplexing in digital images using virtual phase conjugation for holographic data storage

Abstract: We experimentally implemented and proved the concept of multiplexing and demultiplexing in digital images using virtual phase conjugation, which was proposed in our previous study. In the experiment, we concluded that two digital images multiplexed in a single signal beam are recorded in a holographic medium, and these images are independently and successfully reproduced. In this method, the digital images are multiplexed by superimposing them on a complex amplitude, and not using volume hologram’s multiplexing. Thus, the exposure amount in the holographic medium is constant regardless of the number of multiplexing of digital images, and the method has great potential for achieving high recording density.

High-power optical fiber laser

Abstract: The invention discloses a high-power optical fiber laser. The laser structurally comprises a residual light collector, a red light/signal light beam combiner, a red light laser, a reverse cladding light mode stripper, a forward pumping pump source module, a forward pumping/signal beam combiner, a high-reflection grating, doped optical fiber, a low-reflection output grating, a reverse pumping/signal beam combiner, a reverse pumping pump source module, a forward cladding light stripper, and output optical fiber with an antireflection film end cap. Based on a linear fabry-perot resonance cavity structure, the forward pumping pump source module and the reverse pumping pump source module, with different wavelengths, provided with narrow-band protection filters are adopted, the forward pumping/signal beam combiner and the reverse pumping/signal beam combiner pump doped optical fiber from the front end and the back end of the doped optical fiber through the high-reflection grating and the low-reflection output grating at the same time, so that multi-kilowatt-class power stable output of the optical fiber laser is achieved, and mutual damage of residual pumping light on two sides to a pumpsource chip is avoided.

Numerical Simulations of Transfer of Spatial Beam Aberrations in Optical Parametric Chirped-Pulse Amplification

Abstract: In this paper, the spatial characteristics of the optical parametric chirped-pulse amplification (OPCPA) process were numerically studied when initial pump beam was aberrated. Numerical results showed that the spatial walk-off effect transferred phase modulation partly to the signal beam as the pump phase was modulated. Moreover, the modulation amplitude became increasingly severe as the nonlinear length extended. In the absence of phase aberration in the initial input signal, the induced phase aberration in the output signal was assumed as the differential form of the pump beam phase. As the pump beam intensity was modulated, the spatial walk-off effect reduced the influence of pump beam noise on beam quality and the angular spectrum but reduced signal gain simultaneously; thus, it may do more harm than good in the OPCPA process. In the case of a non-diffraction-limited pump beam, the greater the beam quality factor , the lower the conversion efficiency of the output signal in the OPCPA process. These results have important guiding significance for optimized design of an OPCPA system for high power laser.

Efficiency measurements for a digital-holography system

Abstract: This paper compares efficiency measurements to predictions for a digital-holography system operating in the off-axis image plane recording geometry. We use a highly coherent 532 nm laser source, an extended Spectralon object, and an Si focal-plane array to perform digital-holographic detection, which provides access to an estimate of the complex-optical field and is of utility to long-range imaging applications. In the experiments, digitalholographic detection results from the interference of a signal beam with a reference beam. The signal beam was created from the active illumination of the extended Spectralon object and the reference beam from a local oscillator which is split off from the master-oscillator 532 nm laser source. To compare efficiency measurements to predictions, an expression was developed for the signal-to-noise ratio, which contains many multiplicative terms with respect to total-system efficiency. In the best case, the measured total efficiency was 15.2% ± 5.8% as compared to the predicted 16.4%. The results show that the polarization and the fringe-integration efficiency terms play the largest role in the total-system efficiency.

Sensing system and method

Abstract: A sensing method, including: emitting a signal beam; sampling the reflected signal at a sensor with a field of view larger than the signal beam; and determining a surface parameter based on the bright and dark regions associated with the sampled signal

Frequency Down-Conversion of Dual-Wavelength Raman Fiber Laser in PPLN-Based Optical Parametric Oscillator

Abstract: We report on frequency down-conversion of dual-wavelength (DW) Raman fiber laser in a periodically poled lithium niobate-based optical parametric oscillator The DW pump source was fixed at 1060 and 1111 nm that was obtained based on stimulated Raman scattering effect by combining a home-made linearly polarized 1060-nm fiber laser and 137-m-long polarization-maintaining passive fiber The total pump power went through three stages, in the latter two of which the 1111-nm wave appeared In the entire experiment, the 1060-nm pump beam achieved parametric oscillation and generated 1626-nm signal beam and 3056-nm idler beam The 1111-nm pump beam generated 3503-nm idler beam based on difference frequency generation (DFG) between itself and 1626-nm signal beam in the second stage With power enhancement, it built independent parametric oscillation in the third stage and generated 1621-nm signal beam as well as 3530-nm idler beam The DW idler power ranged from 394 to 778 W in the latter two stages The power and efficiency characteristics in frequency conversion processes of 1060- and 1111-nm pump beams were also analyzed separately

High power picosecond parametric mid-IR source tunable between 1.7 and 2.6 μm.

Abstract: A high-average-power wavelength-tunable picosecond mid-IR source based on parametric downconversion has been developed. The conversion system consists of two stages, optical parametric generator and optical parametric amplifier (OPA), which are pumped by an Yb:YAG thin-disk laser operated at 77 kHz repetition rate, 1030 nm wavelength, and pulse duration down to 1.3 ps. The signal beam is amplified up to 9.2 W and the idler up to 5.4 W at OPA pumping of 43 W. Tunability between 1.70 and 1.95 μm for the signal and between 2.2 and 2.6 μm for the idler has been achieved. The system is rather simple and power scalable.

Secure free space communication with vortex beams

Abstract: Security is an increasingly important issue in modern communication. We propose a concept for secure detection of vortex beams in free space optics (FSO). The transmitted signal is composed of a Gaussian beam together with a low powered vortex beam. For each vortex mode, we select the detectors with the maximum received power for the particular signal, depending on the spatial distribution probability of the signal beam. Eavesdroppers have no way of knowing which patterns are relevant for the transmitted signal. We perform a numerical calculation for maximal signal detection and security. Applications include l free space communication.

Optical ultrafast characterization of copper oxide (CuO) nanocrystal charge-carrier dynamics

Abstract: A thorough investigation of copper oxide, specifically cupric oxide (CuO), is performed in the following work with a focus on CuO’s ultrafast free-carrier dynamics and bandstructure. An above-bandgap control beam and below-bandgap signal beam are utilized in transient absorption spectroscopy to gain insight on CuO nanocrystals’ recombination and relaxation dynamics at varying control beam fluences. The authors witnessed three distinct time constants, the first of which changed with control beam fluence between 330 and 630 fs, while the second and third remained constant at 2 ps and 50 ps, respectively. The first time constant is attributed to momentum relaxation from valence band carrier-carrier scattering and exciton-exciton annihilation. The second time constant is attributed to energy relaxation from valence band carrier-phonon scattering. The third time constant is attributed to trapping and recombination as a result of the CuO nanocrystals’ increased trap state density. The findings of this work provide a basis for future research on this emerging CuO nanocrystal system.

Apparatus for manufacturing holographic optical element, and apparatus for reconstructing holograms

Abstract: An apparatus for manufacturing a hologram includes a holographic optical element on which a first interference pattern of a first signal beam and a first reference beam is recorded and a second interference pattern of a second signal beam modulated by a Fourier lens and a second reference beam is recorded. Also, an apparatus for reconstructing a hologram by using the holographic optical element is provided.

Surface speed interferometer is reflected wantonly in many sensitivity that branch's target is unanimous

Abstract: The utility model belongs to the technical field of optical measurements, concretely relates to surface speed interferometer is reflected wantonly in many sensitivity that branch's target is unanimous, its structure includes source of illumination, the illumination beam splitter, imaging lens, middle image planes and signal beam splitter, the laser that source of illumination sent focuses on in the target surface through imaging lens after the reflection of illumination beam splitter again, doppler signal light by the target surface reflection is assembled in middle image planes through imaging lens, then get into a plurality of measurement branches after the beam splitting of signal beam splitter, it includes along the collimating mirror of light path spread direction setting to measure the branch, the interferometer, convergent mirror and streak camera, streak camera is the streak camera who does not take the slit, is provided with the slit in the middle image planes. The utility model discloses an it can realize that many streak camera have the absolute unanimous target that awaits measuring to set up the sharing slit. Measure and simultaneous when finding the solution in many sensitivity, can establish to overlap more accurately and separate, avoided many sensitivity to measure the mistake in computation because of target sighting error leads to.

A superconduct heterodyne integrated receive

Abstract: The invention discloses a superconducting heterodyne integrated receiver, which adopts a BSCC-THz source as the local oscillator and a superconducting Josephson tunnel junction as the mixer. The reference signal beam and the signal beam to be measured are converged and irradiated to the mixer respectively. After signal amplification, the mixer is inputted into a spectrum analyzer for signal spectrum analysis. The BSCCO-THz source and mixer work in their respective vacuum and low temperature environments. The superconducting heterodyne integrated receiver is highly modular, the mixer and the accessory circuits, intermediate frequency amplifiers, and BSCCO-THz source and its accessory circuits are effectively integrated, and can be replaced and repaired in time if problems arise. The BSCCO-THz source and mixer are placed in different low temperature and vacuum environments to ensure that they work at their respective appropriate operating temperatures. The operating temperature of BSCCO-THz source is adjusted according to frequency requirements, thus preventing the mixer state from being affected, making the temperature control of the whole system more convenient, at the same time, avoiding electrical interference, and reducing the noise of the system when working.

Dual-Wavelength Mid-Infrared Generation Using Intracavity Stimulated Raman Scattering of PPLN

Abstract: We report, to the best of our knowledge, the first demonstration of a continuous-wave, dual-wavelength (DW) mid-infrared optical parametric oscillator (OPO) based on the stimulated Raman scattering (SRS) effect of periodically poled lithium niobate (PPLN). The OPO was pumped by two independent fiber lasers, one being fixed at 1018 nm and the other being tunable. The high-power 1018-nm source built parametric oscillation, induced SRS effect in PPLN and generated 1495-nm signal beam as well as 1506-nm Raman beam. The tunable fiber laser was set at 1080 nm and the phase-matched difference frequency generation (DFG) occurred between the 1506-nm Raman beam and 1080-nm pump beam. Finally, DW idler beam located at 3189 and 3819 nm was obtained whose power ranged from 8.044 to 8.115 W, in which the 3189-nm idler power made up the majority of about 8 W and the maximum 3819-nm idler power reached 0.154 W. The slope and conversion efficiency of DFG and OPO processes was also discussed separately.

Rectangular waveguide-based sweep frequency microwave imaging system based on matrix decomposition and detection method

Abstract: The invention relates to a rectangular waveguide-based sweep frequency microwave imaging system based on matrix decomposition. The rectangular waveguide-based sweep frequency microwave imaging systemcomprises a computer, a display unit, an XYZ displacement mechanism, a directional signal beam splitting circuit, a signal analysis unit, a microwave signal source and a waveguide, wherein the computer is connected with the XYZ displacement mechanism by a serial port, controls the XYZ displacement mechanism to move the waveguide and executes data acquiring and processing; the display unit displaysa final detection result image; the XYZ displacement mechanism moves the rectangular waveguide or a detected object, realizes control over the detection distance between the waveguide and the detected object and acquires detection data; the directional signal beam splitting circuit separates and directs part of a transmission signal and a reflection signal; the waveguide is a rectangular openingwaveguide and realizes transmitting and acquiring functions of a microwave signal; the signal analysis unit is a vector network analyzer and realizes measurement of microwave signal amplitude and phase; the microwave signal source transmits the microwave signal to the waveguide by the directional signal beam splitting circuit; the waveguide is connected with the signal analysis unit by a coaxial cable; and the computer is connected with the signal analysis unit by a general purpose interface bus (GBIP).

Multifunctional optical element and method using multiple light scattering

Abstract: Disclosed herein are a multifunctional optical element and method using multiple light scattering. An optical control method using multiple light scattering may include the steps of splitting coherent light into a signal beam and a reference beam, controlling the wavefront of the signal beam, forming an interference pattern by making the signal beam having the controlled wavefront and the reference beam incident on photorefractive materials, recording the interference pattern on the photorefractive materials, reconstructing the signal beam having the controlled wavefront by the interference pattern by radiating the reference beam to the photorefractive materials on which the interference pattern has been recorded again, and controlling the properties of light passing through complex media based on multiple light scattering generated by the complex media as the reconstructed signal beam is incident on the complex media.

Phased array beam tracking using beam gain coding

Abstract: A system for phased array signal beam tracking includes a phased array transmitter configurable for transmitting a signal beam at a selected transmit beam angle from a plurality of different transmit beam angles. The system also includes a beam gain angle coding assembly configured for modulation of a gain of the signal beam to produce a resulting gain profile of the signal beam. The resulting gain profile includes offset angle coding that indicates an offset incident angle of the signal beam at a receiving antenna.

Point-Spread Function Engineering in Upconversion Imaging

Abstract: We demonstrate an upconversion based 4-fimaging system and investigate how its point-spread function can be altered by spatially manipulating the amplitude and/or phase profiles of the otherwise Gaussian mixing field. This is accomplished by imaging different amplitude and phase masks illuminated by the mixing field into the Fourier plane of the imaging system where nonlinear sum frequency mixing occurs. A bulk lithium niobate crystal is used as the nonlinear medium and an Er-Tm fiber laser is used to generate the mixing and the signal fields at 1550 nm and 1877 nm, respectively. Object information is probed by the 1877 nm signal beam and upconverted to form an image at 849 nm, which allows for image acquisitioning using an inexpensive room-temperature Si camera.

Space angle measurement system and method of increasing range of receiving signal beam

Abstract: The invention provides a space angle measurement system including a first polarized light generation unit, a first polarized light receiving and measuring unit, and a dual-rotation rhombic prism unitlocated between the first polarized light generation unit and the first polarized light receiving and measuring unit. A method of increasing range of receiving signal beam with the space angle measurement system includes the steps of: the first polarized light generation unit emits linear polarized light; the dual-rotation rhombic prism unit adjusts the propagation direction of the linear polarized light beam to increase receiving area and guarantee that the linear polarized light enters the first polarized light receiving and measuring unit vertically; the first polarized light receiving andmeasuring unit then receives the vertically incident linear polarized light. Through rotation of the dual-rotation rhombic prism, the range that the first polarized light receiving and measuring unitreceives the polarized light signal beam is increased; then through four times of reflection by the dual-rotation rhombic prism, the polarized light signal beam vertically enters the first polarized light receiving and measuring unit.

High-power signal beam combiner and manufacturing method thereof

Abstract: The invention discloses a high-power signal beam combiner and a manufacturing method thereof. The high-power signal beam combiner comprises a plurality of input optical fibers, a beam combining optical fiber and an output optical fiber, wherein each input optical fiber comprises an input fiber core and an optical fiber input cladding layer which wraps the outer wall of the input fiber core; the output optical fiber comprises an output fiber core and an optical fiber output cladding layer for wrapping the outer wall of the output fiber core; the cross section of the optical fiber input claddinglayer is in a fan shape or a hexagonal shape and is provided with a groove and/or a bump in the axial direction; the plurality of input optical fibers are mutually nested together to form the beam combining optical fiber; each fiber core in the beam combining optical fiber is connected with the output fiber core; the beam combining cladding layer of the beam combining optical fiber is connected with the output fiber core or the optical fiber output cladding layer; by adoption of the structure and the method disclosed in the invention, a fused biconical taper or acid corrosion process is not needed, so that quality deterioration of the light beams is effectively avoided; and air bubbles cannot be generated in the optical fiber input cladding layer of the input optical fiber, so that it isensured that the signal can be subjected to total reflection transmission in the input optical fiber, the signal light bearing capacity is stronger, and high-power signal transmission can be facilitated.

Flexoelectro-optic effect and two-beam energy exchange in a hybrid photorefractive cholesteric cell with a short-pitch horizontal helix.

Abstract: We develop a theoretical model to describe two-beam energy exchange in a hybrid photorefractive cholesteric cell with a short-pitch helix oriented parallel to the cell substrates (so-called uniformly lying helix configuration). Weak and strong light beams incident on the hybrid cell interfere and induce a periodic space-charge field in the photorefractive substrate of the cell, which penetrates into the cholesteric liquid crystal (LC). Due to the flexoelectro-optic effect an interaction of the photorefractive field with the LC flexopolarization causes the spatially periodic modulation of the helix axis in the plane parallel to the cell substrates. Coupling of a weak signal beam with a strong pump beam at the LC permittivity grating, induced by the periodically tilted helix axis, leads to the energy gain of the weak signal beam. Dependence of the signal beam gain coefficient on the parameters of the short-pitch cholesteric LC is studied.