Sum-frequency Beam Research Articles

Quadripartite quantum steering generated by single-pass cascaded nonlinear processes

Quantum steering has become an important resource for quantum information due to its unique asymmetry. In this paper, quadripartite quantum steering generated by single-pass nondegenerate optical parametric amplification cascaded with a sum-frequency process is investigated. Firstly, an idler beam is produced by a different-frequency process between pump and signal. Secondly, a sum-frequency beam is generated by a cascaded sum-frequency process between idler beam and pump in the same optical superlattice. Quadripartite quantum steering among pump, signal, idler and sum-frequency beams is demonstrated based on the criterion for multipartite quantum steering. The influences of nonlinear coupling coefficients κ, dimensionless propagation length ξ, and the initial values of pump and signal on the variation characteristic of the quadripartite steering are also investigated. The results indicate that slightly larger nonlinear coupling coefficients of cascaded nonlinear processes and weaker signals can achieve better quadripartite quantum steering. This simple quadripartite quantum steering preparation scheme does not require a resonant cavity and is easier to implement experimentally, with potential applications in quantum communication and computing.

Genuine quadripartite quantum steering generated by an optical parametric oscillation cascaded with a sum-frequency process

Quantum steering is the essential resource for quantum information processing. In this letter, a scheme is proposed to generate genuine quadripartite Einstein-Podolsky-Rosen (EPR) steering by an optical parametric oscillation cascaded with a sum-frequency process. Idler beam is generated by a difference frequency generation process between pump and injected signal in an optical superlattice. Then, a sum-frequency beam is produced by the cascaded sum-frequency process between pump and idler beams in the same optical superlattice by the quasi-phase-matching technique. The genuine quadripartite EPR steering among pump, signal, idler, and sum-frequency beams is confirmed in this scheme by applying a criteria for genuine multipartite EPR steering. The variation properties of the EPR steering with pump and nonlinear coupling coefficients are also discussed.

Polarization transformation of three light beams in sum-frequency generation in isotropic chiral medium in case of high conversion efficiency

Sum-frequency generation in the case of coaxial interaction of elliptically polarized Gaussian beams of fundamental radiation in isotropic chiral medium was studied. The system of three equations of nonlinear diffraction was solved numerically without the assumption of undepleting fundamental (‘pump’) waves. It has been shown that only for small (less than 0.1) values of nonlinear coupling coefficient of the interacting waves can their propagation be described within the framework of such approximation with precision of a few tenths of a percent. However, the results of the undepleting pump approximation are remarkably different from those obtained in the numerical solution of a system of nonlinear equations for greater values of nonlinear coupling coefficient. In the first turn, this difference appears in the amplitude and polarization of the sum frequency beam. When the nonlinear coupling coefficient is of the order of unity, its further increase does not lead to the growth of the conversion efficiency, which remains of the order of 10−2. At the same time, there appear to be notable changes of intensity and polarization of light in the transverse sections of the beams at fundamental frequencies.

Transfer efficiency of angular momentum in sum-frequency generation and control of its spin and orbital parts by varying polarization and frequency of fundamental beams

Considering sum-frequency generation in an isotropic chiral nonlinear medium, we analyze the transfer of the spin angular momentum of fundamental elliptically polarized Gaussian light beams to the signal beam, which appears as the superposition of two Laguerre–Gaussian modes with both spin and orbital angular momentum. Only for the circular polarization of the fundamental radiation is its angular momentum fully transferred to the sum-frequency beam; otherwise, part of it can be transferred to the medium. Its value, as well as the ratio of spin and orbital contributions in the signal beam, depends on the fundamental frequency ratio and the polarization of the incident beams. Higher energy conversion efficiency in sum-frequency generation does not always correspond to higher angular momentum conversion efficiency.

Quadripartite continuous-variable entanglement generation by nondegenerate optical parametric amplification cascaded with a sum-frequency process

Quadripartite continuous-variable (CV) entanglement with different optical frequencies can be generated by nondegenerate optical parametric amplification cascaded with a sum-frequency process in only one optical superlattice. Firstly, the idler beam is generated by a different frequency process between pump and signal beams. Then, the sum-frequency beam will be generated by a cascaded sum-frequency process between pump and idler beams in the same optical superlattice. The conversion dynamics of the cascaded nonlinear processes is investigated by using a quantum stochastic method. The quantum correlations among pump, signal, idler and sum-frequency beams are calculated by applying a sufficient inseparability criteria for quadripartite CV entanglement. The results show that quadripartite CV entangled beams can be produced by this single-pass cascaded nonlinear process in one optical superlattice.

Generation of bright three-color tripartite continuous variable entanglement via the sum-frequency generation

We theoretically show that bright three-color tripartite continuous-variable entanglement can be generated directly by the process of triply resonant sum-frequency generation using a periodically poled supperlattice. It is demonstrated that two reflected pump beams and the output sum frequency beam are all entangled with each other according to the sufficient inseparability criterion for multipartite continuous variable (CV) entanglement. The dependence of the steady state region and the entanglement on system parameters are discussed. By utilizing the up-conversion process, the generated three entanglement fields have macroscopic intensities as soon as the pump fields are turned on.

Theoretical analysis of a new T-shaped thermo-stable telescopic resonator for sum-frequency beam generation by 1064 and 1319 nm lasers

A new shorter T-shaped thermo-stable telescopic resonator is demonstrated in this Letter. By means of thick lens model, a longer 1064-nm telescope linear cavity is designed and simulated first by analyzing the influence of the distance between every two optical elements on the fundamental mode radius on the end mirror and the system stable zone. On the basis of the parameters analyzed, a shorter telescopic composite laser system is presented for both the 1064 and 1319 nm operating lasers that will be applicable to high-quality yellow laser generation by means of sum-frequency technology.

Space-selective enhancement of blue photoluminescence in gallium germanosilicate glass through laser-induced nanostructuring

Crystalline gallium oxide is known to possess UV-excited blue photoluminescence together with one of the widest band gaps among transparent conducting oxides, with a transmittance range extending from the visible to the near-UV range, thus making it a promising material for efficient solar-blind UV-to-visible converters. In the present paper, we report for the first time laser-induced space-selective precipitation of γ-Ga2O3 nanosized crystals in alkali gallium germanosilicate glass using a sum frequency beam (271nm) of a copper vapor laser. At the glass surface, the laser writing process generates transparent nanostructured channels which emit broadband blue photoluminescence (centered at about 460nm) under UV exposure, with excitation efficiency peaked at about 260nm. Only much weaker blue photoluminescence can instead be observed in the starting non-irradiated glass from the precursor stage of the nanocrystallization. Spectral properties of light emission in the nanocrystallized regions are similar to those of earlier studied bulk nanostructured material produced from the same composition by heat treatment. Laser-written photoluminescent patterns in the studied glass provide advanced opportunities for developing novel solar-blind UV detectors.

Transversal structure of a sum-frequency beam generated from the surface of a chiral medium

In this work we study sum-frequency generation from the surface of an isotropic chiral medium in arbitrary interaction geometry of the paraxial light beams at fundamental frequencies. The analytical formulae have been deduced completely describing the transversal spatial distribution of the electric field in the light beam at sum-frequency. Even in a zero-order approximation on the divergence angles of the beams the transversal spatial intensity distribution in the signal beam is elliptic Gaussian, and its shape depends only on the geometry of incidence, the transversal dimensions and the frequencies of the fundamental beams. Within the first-order approximation approach, generally, the polarization state of light is distributed inhomogeneously in the reflected signal beam cross section, and the transversal intensity distribution is not Gaussian. But when the fundamental beams are not focused tightly enough, the non-Gaussian part of the field is negligibly small, compared to the Gaussian part with uniform polarization distribution. However, at larger angles of incidence the non-Gaussian contribution becomes comparable with the Gaussian zero-order part of the field (or exceeds it) even in the case of slightly focused fundamental beams. In this case the transversal distributions of intensity and polarization of light become very sophisticated.

Formation of an inhomogeneously polarised light beam at the sum frequency by two collinear elliptically polarised Gaussian beams focused into a chiral medium

The distribution of polarisation of a light field in the cross section of a beam at the sum frequency is investigated upon the collinear interaction of two elliptically polarised Gaussian beams in a nonlinear isotropic gyrotropic medium. It is shown that the ellipticity, the angle of rotation of the principal axis of the polarisation ellipse, and the rotation direction of the electric field vector of radiation at the sum frequency in the beam cross section strongly depend on the angle in the polar coordinate system. The ranges of parameters of elliptically polarised fundamental Gaussian beams are found where the cross section of the sum-frequency beam is divided into sectors with different rotation directions of the electric field vector. The equations of the straight lines determining the boundaries of these sectors contain parameters specifying the shape and orientation of polarisation ellipses of the fundamental waves and the ratio of their wave vectors. In the case of opposite circular polarisations of these waves, the ellipticity of the sum-frequency beam does not change in the beam cross section and the principal axes of polarisation ellipses of the light field are oriented perpendicular to the radius in polar coordinates.

Quantum Interference in Electron-Hole Generation in Noncentrosymmetric Semiconductors

We show that, when fundamental optical beams are present in a noncentrosymmetric medium simultaneously with their sum-frequency beam, quantum interference between single- and two-photon transitions modifies the net absorption, if the sum frequency corresponds to an energy greater than the band gap. At a macroscopic level this effect can be related to the imaginary part of a second-order susceptibility and can be used to coherently control carrier populations and optical absorption. We illustrate this novel effect using phased 1550 and 775 nm, 120 fs pulses incident on GaAs at 295 K.

Sum frequency beam analysis for the determination of the temporal characteristics of ultrashort light pulses

An extension of the single-shot second harmonic beam method proposed earlier for picosecond pulse duration measurements is presented for the case of two incident pulses of differing frequencies, durations and transverse sizes. The solution of the wave equation for noncollinear sum frequency generation in a nonlinear crystal by two Gaussian, spatially limited ultrashort pulses is given. It is shown that the width (τ 1 2 +τ 2 2 )1/2 of the temporal cross-correlation function of the two pulses can be deduced from the spatial energy distribution of the sum frequency beam. The method can be used e.g. in the case of a relatively weak secondary pulse obtained in some nonlinear processes. Preliminary experimental results demonstrating the possibilities offered by the method are presented.

Parametric acoustic receiving array. II. Experiment

A series of experiments was conducted with a 48-ft parametric receiving array at a pump frequency of 90 kHz. An omnidirectional transducer was used with either a rectangular or a square piston transducer. Each of the three transducers could be used as either pump or receiver, so that a variety of parametric receiving array configurations could be realized. The piston transducer could be independently rotated, to examine the effects of misalignment. Theoretical and experimental results are compared for the parametric receiving array with several transducer arrangements. With either the pump transducer or the receiver misaligned, the difference frequency beam pattern is asymmetrical and is the mirror image of the sum frequency beam pattern. The agreement between theory and experiment was excellent. Subject Classification: 25.35; 30.85.

Parametric acoustic receiving array. II. Experiment

A series of experiments was conducted with a 48-ft parametric receiving array with a pump frequency of 90 kHz. In the experiments, an omnidirectional transducer was used with either a rectangular piston transducer or a square piston transducer. Each transducer could be used as either the pump transducer or the receiver so that a variety of parametric receiving array configurations could be realized. A small rotator was used to allow independent rotation of the piston transducer for measurement of the effects of misalignment of the piston transducer. Theoretical and experimental results are compared for the parametric receiving array with several transducer arrangements. With either the pump transducer or the receiver misaligned, the difference frequency beam pattern is an asymmetrical beam pattern and is the mirror image of the sum frequency beam pattern. The agreement between the theory and the experiment was excellent.

Parametric beam-steering technique for acoustic waves with applications to signal processing

It is predicted that two acoustic waves crossing at right angles in a suitably dispersive nonlinear medium will generate a sum-frequency beam in a direction determined by the ratio of their frequencies. This phenomenon makes possible new switching, variable-delay, filtering and correlation devices.