Phase-conjugate Resonator Research Articles

Color-switching in an optical parametric oscillator using a phase-conjugate mirror

We construct a phase-conjugate resonator which passively produces stable pulses that alternate between the probe and the conjugate colors. The requisite phase-conjugate mirror inside the resonator is constructed using non-degenerate four-wave mixing (4WM) in rubidium vapor. The glancing-angle phase-conjugate mirror is a 100% output coupler, and therefore this resonator is unusual in that no light circulates the cavity more than once. Without the gain of the phase-conjugate mirror, the cavity boundary conditions, and thus resonant modes, are not defined and therefore can be tuned by the pump. The output of the optical parametric oscillator that is formed above threshold can passively mode-lock. The phase-conjugate mirror removes thermal or acoustic instabilities that are on a MHz or slower timescale. This work provides a new method for stable pulsing using phase-conjugate optics, and suggests a platform for producing mode-locked pulses with squeezed light, as the 4WM process has already demonstrated quantum correlations.

Duffing spatial dynamics induced in a double phase-conjugated resonator

This work presents a mathematical description of light beam behavior inside a double phase-conjugated resonator when an optical device capable of generating Duffing-like map dynamics is introduced in the cavity. It will be shown that the internal optical device may control the light spatial dynamics inside a ring resonator with double phase-conjugated mirrors. The resonator is constructed using one perfect plane mirror intercalated with two ideal phase-conjugated mirrors. The ABCD matrix formalism used to find the general iterative expressions describes the optical beam state after n round trips, showing paraxiality conservation along the entire process. The characteristics of the internal optical device are discussed and its transformation matrix is presented.

Tinkerbell beams in a non-linear ring resonator

In this article the dynamical behaviour of a beam that behaves according to a Tinkerbell map (i.e. Tinkerbell beam), within a nonlinear ring phase-conjugated resonator is modelled. The ABCD matrix of an optical device able to generate a two dimensional Tinkerbell map is found in terms of the map parameters, the state variables and the resonator parameters. For the first time to our knowledge the conditions in order to obtain the dynamics of a beam behaving according to a Tinkerbell map are found within an optical resonator. Finally some of the main technical problems to build a resonator intracavity element able to produce Tinkerbell beams are presented.

Controlling optical spatiotemporal chaos of coupled phase-conjugate map system with nonlinear feedback

The optical phase-conjugate resonator consists of one normal mirror and one phase-conjugate mirror made of an instantaneous response lossless Kerr medium. Using the nonlinear feedback, we control the temporal chaos in the phase-conjugate resonator and spatiotemporal chaos in the coupled phase-conjugate map system. Stable control has been realized. The simulation shows that this controlling technique can be implemented easily in practical systems just by adjusting the feedback strength. The in-advance knowledge of the dynamic system is not required. The results are useful to theoretical analysis of chaos in phase-conjugate resonators.

The investigation of compound YAG phase-conjugate resonator

How to improve the quality of output beam of phase-conjugation cavity is a problem. And there are a few reports on how to improve the quality of output beam mode [1]. On this paper, the output characteristic of compound phase-conjugate resonator was reported. The experiment results indicated that it has high output energy and excellent mode. The output energy is 7.4 mJ, and the width of it is about 15 ns. The results of pulse widths and output energies and beam profiles were given and it indicates that using the compound cavity is a useful and easy method to improve the quality of beam mode.

High Quality 7.5 W Continuous-Wave Operation of a Nd:YVO4 Laser with a Rh:BaTiO3 Phase Conjugate Mirror

Laser oscillation of a diode-pumped Nd:YVO4 phase conjugate resonator with a photorefractive ring phase conjugate mirror has been demonstrated. A 7.5 W continuous-wave (CW) output with high beam quality was obtained. Slope efficiency of 46% and optical extraction efficiency of 33% were achieved. Standard variance of the output power fluctuation was 2.3%.

General scattering matrix solutions to vector four wave mixing

In this paper, a scattering matrix method to solve the fully nonlinear vector four wave mixing problem in nonoptically active photorefractive materials is presented. Specific solutions are given for anisotropic and isotropic media as utilised in standard four wave mixing systems and in ring passive phase conjugate resonators. Paraxial wave equations and an optimally (π/2) phase shifted transmission grating are assumed. The theory is developed for linear polarisations and accounts for pump depletion. Solutions for arbitrary orientation of beams are used to explore the conditions by which vector phase conjugation can be simply achieved.

Communicating with waves between volumes: evaluating orthogonal spatial channels and limits on coupling strengths

A rigorous method for finding the best-connected orthogonal communication channels, modes, or degrees of freedom for scalar waves between two volumes of arbitrary shape and position is derived explicitly without assuming planar surfaces or paraxial approximations. The communication channels are the solutions of two eigenvalue problems and are identical to the cavity modes of a double phase-conjugate resonator. A sum rule for the connection strengths is also derived, the sum being a simple volume integral. These results are used to analyze rectangular prism volumes, small volumes, thin volumes in different relative orientations, and arbitrary near-field volumes: all situations in which previous planar approaches have failed for one or more reasons. Previous planar results are reproduced explicitly, extending them to finite depth. Depth is shown not to increase the number of communications modes unless the volumes are close when compared with their depths. How to estimate the connection strengths in some cases without a full solution of the eigenvalue problem is discussed so that estimates of the number of usable communications modes can be made from the sum rule. In general, the approach gives a rigorous basis for handling problems related to volume sources and receivers. It may be especially applicable in near-field problems and in situations in which volume is an intrinsic part of the problem.

Raman phase conjugate resonator for intracavity aero-optic turbulence aberration correction

A cw degenerate phase conjugate resonator (PCR) with intracavity aero-optic turbulent flow is demonstrated using sodium vapor pumped with a low intensity cw laser. A turbulent helium jet at a high flow velocity of 250 m/s and forcing frequency of 18 kHz generated the spatio-temporal aberrations. The intracavity normalized peak-to-peak intensity fluctuations at 18 kHz measured with a pinhole-detector are ten times smaller in the corrected beam than in the aberrated beam. The threshold pump intensity for the resonator is ∼4.5 W/cm 2 in the absence of the turbulent flow. The pump frequency is tuned well within the Doppler width of the Na D 1 transition. Evidence of a degenerate (laboratory frame) double-Λ mechanism involving Zeeman sublevels is also shown.

Self-pumped phase-conjugate resonator with two-pass four-wave mixing in a diode-pumped Nd:YAG amplifier

We investigate both theoretically and experimentally a self-pumped phase-conjugate resonator with two-pass four-wave mixing in a diode-pumped Nd:YAG amplifier. A transient model is presented to fit the energy and temporal results of the experiment. The influence of the input energy in the injected configuration and the influence of the output coupler reflectivity and diode pump energy in the self-starting configuration are analyzed. In the injected case a maximum phase-conjugate reflectivity of 32 is obtained. In the self-starting case a TEM00 mode of 5.5 mJ in a 20-ns single-longitudinal-mode pulse is produced with a 10% reflectivity output coupler.

Spatial channels for communicating with waves between volumes

I show that there is an exact, complete method for finding the orthogonal spatial channels, or communications modes, between two arbitrary volumes, and the associated connection strengths, for the case of scalar waves. I also show that the sum of the squared connection strengths is given exactly by a simple volume integral. The method is illustrated by a calculation for a particular extreme pair of volumes, and the communications modes are interpreted physically as the modes of a double phase-conjugate resonator.

Demonstration of a phase conjugate resonator using degenerate four-wave mixing via coherent population trapping in rubidium

We demonstrate a ring cavity laser using the gain mechanism of a four-wave mixing process, mediated by two-photon Zeeman coherence resulting from coherent population trapping in a rubidium vapor cell. The cell acts as an amplifying phase conjugate mirror at one corner of the ring cavity. Even though the fundamental process requires non-degeneracy between the probe and the conjugate in the atom's frame, they are degenerate in the laboratory frame, via selection of a moving band of atoms for the gratings. As such, no frequency shifting is necessary in the cavity. The polarization orthogonality of the probe and the conjugate is compensated by an intra-cavity quarter wave plate.

Off-Bragg model for the photorefractive phase-conjugate resonator

The spatiotemporal dynamics of a photorefractive phase-conjugate resonator is modeled in three spatial dimensions and time. The transverse dimensions are sampled on a lattice in wave vector space while the longitudinal dimension is sampled in real space. Numerical simulations are shown to agree well with experimental data. At low Fresnel number, the cavity geometry and the transverse component of the Bragg mismatch are shown to dominate the dynamics, while the effects of the longitudinal component of the mismatch are shown to become important in representing the complex dynamics observed at higher Fresnel numbers.

Phase locking of multiple stimulated Brillouin scattering by a phase-conjugate laser resonator

We report the demonstration of ultrashort pulse generation by multiple stimulated Brillouin scattering in a phase-conjugate laser resonator with a Nd:YAG gain medium. We show that a backward-traveling acoustic wave, in addition to the usual forward-traveling acoustic wave, plays an important role in the temporal and the spectral dynamics of the interaction. A simplified steady-state small-signal gain theory is presented that identifies the conditions for phase locking.

Experimental modal analysis of the spatiotemporal dynamics of a linear photorefractive phase-conjugate resonator

An experimental modal analysis is performed on the transverse patterns of a photorefractive phase-conjugate resonator with a Karhunen–Loeve decomposition from which the most significant eigenvectors of the covariance matrix or the cross-spectral density matrix of the intensity fluctuations are defined and interpreted as the active eigenmodes of the resonator. The dynamics are studied as a function of the cavity Fresnel number and the angular tilt between the external pump beams (Bragg mismatch). As the Fresnel number is varied it is shown that states with the same modal decomposition may be temporally periodic or aperiodic. The Bragg mismatch is shown to be responsible for breaking the rotational symmetry of the system, changing the spatial complexity of the patterns, and changing the characteristic speed of the nonstationary patterns.

Generation of squeezed photons by coupled phase-conjugate resonators

We study the generation of squeezed photons by coupled resonators with phase-conjugate mirrors. A large amount of squeezing is obtained by an interference effect between them even when optical nonlinearities are small. Squeezing can be controlled by the phase difference of the laser beams pumping the phase-conjugate mirrors. This is analogous to the Josephson supercurrent.

Self-pumped phase conjugate resonators and mirrors for use in optical associative memories

The paper begins by reviewing research on optical associative memories employing phase conjugate mirrors and resonators. Novel work on the use of self-pumped phase conjugate mirrors (SPPCMs) during recording to improve holographic diffraction efficiencies for up to 24 angularly multiplexed gratings is described and the first demonstration of a multimode phase conjugate resonator, with up to 21 modes, operating between two SPPCMs (one of which was induced in a non-degenerate manner) via holographic gratings is shown.

Long-pulse self-starting stimulated-Brillouin-scattering resonator

We demonstrate, for the first time to our knowledge, a self-starting stimulated-Brillouin-scattering phaseconjugate resonator in a flash-lamp-pumped dye-laser system. The brightness of the laser is increased by a factor of 40 compared with that of an equivalent plane-]plane conventional resonator.

Model of Vortices Nucleation in a Photorefractive Phase-conjugate Resonator

Abstract The nucleation of a pair of vortices in the field of a boundary dominated confocal photorefractive phase-conjugate resonator is studied in detail. A phase instability is seen to precede the nucleation which occurs when the phase step reaches a threshold of π. The validity of a scenario based on the competition of a few modes is verified experimentally using a multichannel optical correlator equipped with matched filters designed to identify the modes presumed by the model.

Improved spatial and temporal performance of a phase-conjugate resonator with an intracavity mode homogenizer

The temporal stability, spatial uniformity, and transverse dimension of the oscillating modes of phase-conjugate resonators have been improved by incorporation of passive intracavity elements designed to homogenize the resonator modes. We have demonstrated a reduction of the gain competition between the modes supported by a resonator by using an intracavity light pipe or a tapered fiber-optic bundle. In one resonator configured for optical data-processing applications, the homogenizers significantly reduced optical turbulence and facilitated expanding the transverse dimension of the mode to support 7 × 103 pixels.