Traveling-wave Parametric Amplifier Research Articles

Bright squeezed-vacuum source with 1.1 spatial mode.

Bright squeezed vacuum, a macroscopic nonclassical state of light, can be obtained at the output of a strongly pumped nonseeded traveling-wave optical parametric amplifier (OPA). By constructing the OPA of two consecutive crystals separated by a large distance, we make the squeezed vacuum spatially single-mode without a significant decrease in the brightness or squeezing.

Simulation and Analysis of Superconducting Traveling-Wave Parametric Amplifiers

Superconducting parametric amplifiers have great promise for quantum-limited readout of superconducting qubits and detectors. Until recently, most superconducting parametric amplifiers had been based on resonant structures, limiting their bandwidth and dynamic range. Broadband traveling-wave parametric amplifiers based both on the nonlinear kinetic inductance of superconducting thin films and on Josephson junctions are in development. By modifying the dispersion property of the amplifier circuit, referred to as dispersion engineering, the gain can be greatly enhanced and the size can be reduced. We present two theoretical frameworks for analyzing and understanding such parametric amplifiers: 1) generalized coupled-mode equations and 2) a finite difference time domain (FDTD) model combined with a small signal analysis. We show how these analytical and numerical tools may be used to understand device performance.

Fundamental eigenmode of traveling-wave phase-sensitive optical parametric amplifier: experimental generation and verification

We investigate experimentally the eigenmodes of a Gaussian-beam-pumped traveling-wave phase-sensitive optical parametric amplifier (PSA). By varying the waist of an input LG(00) signal mode, we show that PSA performance improves with increasing spatial overlap between the input and the theoretically predicted fundamental eigenmode. For optimum waist, we report amplification and deamplification markedly higher than those observed for the traditional case of signal waist=√2× (pump waist). Lastly, we demonstrate the generation and verification of the PSA fundamental eigenmode.

Optimization of gain in traveling-wave optical parametric amplifiers by tuning the offset between pump- and signal-waist locations

We present experimental demonstration and modeling of the optimization of a phase-sensitive optical parametric amplifier by tuning the relative position between the pump and signal beam waists along the propagation direction. At the optimum position, the pump beam focuses after the signal beam, and this departure from colocated waists increases with increasing pump power. Such optimization leads to more than 3dB improvement in the measured deamplification response of the amplifier.

Quantum properties of a spatially-broadband traveling-wave phase-sensitive optical parametric amplifier

We present the quantum theory of a spatially-multimode traveling-wave phase-sensitive optical parametric amplifier (OPA) pumped by a beam with arbitrary spatial profile. By using Green's functions of the classical OPA, we derive the normally-ordered quadrature correlators at the OPA output, which provide complete quantum description of the phase-sensitive OPA and enable determination of its independently-squeezed eigenmodes. Two analytically treatable examples of plane-wave pump and infinite spatial bandwidth of the crystal are discussed in detail.

Numerical simulation of spatial fluctuations in parametric image amplification

We study the properties of the spatial fluctuations in the far-field parametric fluorescence output of a type 1 degenerate traveling-wave parametric amplifier. Results of a semi-classical simulation are compared with experiments in a LBO crystal. This simulation is then used to predict amplified images of a continuous background, in a phase-sensitive as well as in a phase-insensitive configuration.

Sum-frequency generation of femtosecond pulses in CsLiB_6O_10 down to 175 nm

Using a 150-mum-thick CsLiB(6)O(10) crystal, we produced 100-fs, >200-nJ light pulses tunable between 175 and 180 nm by sum-frequency generation at a 1-kHz repetition rate with an all-solid-state laser system mixing the fourth harmonic of a femtosecond Ti:sapphire regenerative amplifier and the idler pulse from a traveling-wave optical parametric amplifier.

Generation of widely tunable harmonic pulses in the UV and VUV from a NIR optical parametric amplifier

We demonstrate the generation of tunable high-order harmonics from the interaction of the signal output of a near-infrared (NIR) traveling-wave optical parametric amplifier (OPA) with the xenon atoms of a pulsed gas jet. By tuning the OPA between 1200 and 1550 nm, we generate widely tunable pulses of ultraviolet radiation up to the ninth harmonic order, around 150 nm. The possibility to cover the VUV region thanks to the full overlap of the tunability ranges of different harmonic orders below 220 nm is also proved.

Laser-diode-seeded single and double stage femtosecond optical parametric amplification in the mid-infrared

Tunable mid-infrared pulses are generated with a MgO:LiNbO3-based traveling-wave optical parametric amplifier in single and double stage operation regime pumped by a 1-kHz Ti:sapphire regenerative amplifier system. For the first time to our knowledge a pulsed laser diode is successfully used in the femtosecond regime as a compact seed source at the signal wavelength where the tunability of the generated idler pulses can be realized by tuning the seed wavelength. Almost transform limited mid-infrared pulses as short as 130 and 160 fs with pulse energies as high as 5 and 15 μJ are produced near 3.5 μm by the single and double stage scheme, respectively. The pulse to pulse fluctuations in both cases do not exceed 2% which corresponds to the stability of the pump source.

Quantum fluctuations in traveling-wave amplification of optical images

We investigate amplification of optical images by means of a traveling-wave optical parametric amplifier. As shown recently for a cavity-based geometry, such a scheme can amplify images without deteriorating their signal-to-noise ratio thus working as a noiseless amplifier. Here we consider a configuration without cavity, which is more realistic for a possible experimental realization. We study in detail the quantum fluctuations of the amplifier and formulate criteria for its noiseless performance. We investigate physical features of noiseless amplification, which take place for both traveling-wave and ring-cavity configurations. We demonstrate how the optimum phase matching of a phase-sensitive wave front of an image (by means of a thin lens or a small displacement of the crystal) can improve the noise performance of the amplifier and bring it to the ultimate value achievable under given physical conditions. We discuss the possibility of using detectors with the area much smaller than the area of the input image elements. We compare our results with those obtained for the ring-cavity configuration.

Laser-diode-seeded operation of a femtosecond optical parametric amplifier with MgO:LiNbO_3 and generation of 5-cycle pulses near 3 μm

A high-power traveling-wave optical parametric amplifier based on MgO:LiNbO3 that is capable of producing extremely short pulses in the 3-µm spectral range when pumped by a femtosecond Ti:sapphire amplifier near 800 nm has been developed. With seeding by 1-ns pulses from a low-power Q-switched microlaser, we demonstrate idler tunability between 3.1 and 3.9 µm at >10-µJ pulse energy and <200-fs pulse duration. The maximum internal conversion efficiency is 40% for a single pass. The extremely high gain factors achieved permit a more compact solution for the seed source, and we also report on successful seeding with a pulsed laser diode in the femtosecond regime, achieving 5-µJ pulse energy and 130-fs pulse duration near 3.5 µm. We have produced nearly transform-limited 50-fs, 2-µJ pulses near 3 µm with a 1-mm-thick MgO:LiNbO3 sample by adding a second pass and employing sub-30-fs pumping.

Investigation of the photon statistics of parametric fluorescence in a traveling-wave parametric amplifier by means of self-homodyne tomography

Photon-number distributions for parametric fluorescence from a nondegenerate optical parametric amplifier are measured with a novel self-homodyne technique. These distributions exhibit the thermal-state character predicted by theory. However, a difference between the fluorescence gain and the signal gain of the parametric amplifier is observed. We attribute this difference to a change in the signal-beam profile during the traveling-wave pulsed amplification process.

Traveling-wave optical parametric amplifier: investigation of its phase-sensitive and phase-insensitive gain response

We experimentally investigate the gain response of a frequency-degenerate but polarization-nondegenerate traveling-wave optical parametric amplifier that consists of a type II phase-matched potassium titanyl phosphate crystal pumped by a frequency-doubled Q-switched mode-locked Nd:YAG laser. Both the optical phase-sensitive and phase-insensitive configurations of the parametric amplifier are studied. Experimental results are in excellent agreement with the theory of an optical parametric amplifier when the Gaussian-beam nature of the various fields is taken into account. In the phase-sensitive configuration a gain of >100 (20 dB) could be easily obtained in the amplified quadrature, which is limited only by the available pump power. Because of gain-induced diffraction and phase fluctuations, however, maximum deamplification in the orthogonal quadrature is limited to <0.5(-3 dB).

Ultrashort pulsed squeezing by optical parametric amplification.

We investigate temporal effects in pulsed squeezing by parametric amplification, including effects of group-velocity dispersion. Our calculations show that the local oscillator pulse used to detect the squeezed field cannot be made shorter than the inverse phase-matching bandwidth of the generation process without degrading the amount of squeezing detected. This result generalizes an earlier result that showed that in the absence of dispersion, the local oscillator pulse duration should approach zero for optimum squeezing detection. We further show that by using local oscillator amplitude and phase pulse shaping it should be possible to achieve more than 40 dB of detectable quadrature squeezing. This is applicable where it is possible to neglect transverse spatial dimensions and diffraction, such as in a waveguide. We derive the s-parametrized quasiprobability evolution equation for the traveling-wave parametric amplifier. As the Wigner representation results in third-order derivatives, we also use the positive-P representation as an exact representation with equivalent Ito stochastic differential equations. This allows us to compare approximate --- but easily simulated --- Wigner representation results with those using the positive-P representation.

Deamplification response of a traveling-wave phase-sensitive optical parametric amplifier

We have investigated the phase-sensitive deamplification response of a traveling-wave degenerate optical parametric amplifier that consists of a type II phase-matched KTP crystal pumped by the second harmonic of a Q-switched mode-locked Nd:YAG laser. Experimental results are in good agreement with the theory of an optical parametric amplifier in which the Gaussian-beam nature of the various fields along with the diffraction of the amplified signal beam is taken into account. Because of the phenomenon of gain-induced diffraction, maximum deamplification is limited to only ≃3 dB.

Simulton solutions for the parametric amplifier

We introduce new simultaneous, multiple-frequency, solitary-wave solutions to the traveling-wave parametric amplifier. Both degenerate and nondegenerate systems are treated including dispersion. These parametric amplifier simultons are shown to exhibit phase-dependent collisions. Spatial solitary waves are also found in the case of cw fields parametrically coupled in a planar waveguide.

Sub-shot-noise microscopy: imaging of faint phase objects with squeezed light

We propose a scheme that uses spatially multimode squeezed light, generated by means of a traveling-wave optical parametric amplifier, with which a faint phase object can be imaged with sensitivity better than the shot-noise limit.

Limits to wideband pulsed squeezing in a traveling-wave parametric amplifier with group-velocity dispersion

A theoretical method is developed to treat wideband pulsed squeezing in a traveling-wave parametric amplifier with group-velocity dispersion. Classical stochastic wave equations that are fully equivalent to operator equations of motion are developed and solved numerically. It is found that squeezing occurs over the entire phase-matching bandwidth, although the degree of squeezing decreases when the pump-pulse duration is shorter than the inverse of this bandwidth.

Inverse Cerenkov Effect and New Phenomena in Non-linear Optics

The optical parametric oscillator and amplifier involving the analogue of the inverse Cerenkov effect is considered, the effect being due to the non-linear interaction between the plane wave of pumping (with a frequency yp) incident at an angle onto an optical waveguide and the waves (with frequencies ys, yv satisfying the relation ys + yv = yp) generated in the waveguide. For the oscillator an appreciable non-linear reflection from (transmission through) the waveguide layer of the pumping wave is discovered and shown to appear in new directions compared to those known in optics. Also, the transformation by the reflection (transmission) of the pumping wave into the waves with new frequencies 2 ys, 2yv is predicted. The possible effect of additional (higher-order) non-linear processes on the oscillator dynamics is discussed. A travelling-wave parametric amplifier involving the analogue of the inverse Cerenkov effect is also considered. Here, differing from the usual optical parametric amplifiers the intens...

Pulse saturation in a traveling wave parametric amplifier

The pulse saturation on a nondispersive traveling wave parametric amplifier is solved in the slowly varying approximation with space and time by reducing the dynamic equations to a degenerate form-of the sine-Gordon equation. If the group velocity of the signal wave differs from that of the pump and idler waves, the signal wave obeys the sine-Gordon equation.