Passive Phase Conjugate Mirror Research Articles

Compact ultra-high gain multi-pass Nd:YAG amplifier with a low passive reflection phase conjugate mirror

We show a compact multi-pass amplifier, based on a single dual-rod laser-head which produces ultra-high gain. A double-pass produced a maximum small signal gain of 4×10 8. Another double-pass was permitted by including a specially designed Brillouin phase conjugate mirror (PCM). This enabled a total gain of 7.7×10 10, which raised an input signal of 10 pJ to 770 mJ output signal. To the best of our knowledge this is the highest gain reported to date from any type of laser amplifier scheme. The amplification system is fairly simple in that it consists of only one dual-rod laser head and hence only a single power supply. We show that this system can be utilized for producing high-energy long temporally-smooth narrow linewidth pulses, as well as high power controllable, temporally-modulated pulses.

Linewidth instability in a semiconductor laser due to feedback from a ring passive phase-conjugate mirror

Linewidth instability in a semiconductor laser due to feedback from a ring passive phase-conjugate mirror

Theoretical Investigation of Photorefractive Ring Passive Phase-conjugate Mirror in the Presence of Asymmetric Transmission

Abstract The performance of a photorefractive ring phase-conjugate mirror is found to be determined by the combined effect of coupling the strength (ΓL), the product (T 1 T 2) and the ratio (T 1/T 2) of the cavity transmissivities along the two directions. The threshold phase-conjugate reflectivity of the device can be changed or controlled by the variation of these three parameters.

Beam quality measurements of a unidirectional self-pumped phase conjugate mirror

The beam quality of the light reflected off a unidirectional ring passive phase-conjugate mirror (PPCM) is considered. A focusing ratio is defined and used to measure the beam quality. The unidirectional ring PPCM can act like a phase conjugator or a static hologram, depending on the time scale of the experiment. The aberration correction properties of each device are compared to that of a conventional mirror.

Optical thresholding and switching using a fiber-coupled phase-conjugate mirror

A fiber-coupled-ring passive phase-conjugate mirror is used to achieve mutual thresholding free of bistability effects and to obtain switching among several mutually incoherent light beams.

Imaging through a dynamic scattering medium with a passive phase-conjugate mirror

Imaging through a dynamic-scattering medium produces low-contrast images due to the added large background of scattered light. A passive phase-conjugate mirror can generate an image with enhanced contrast; the background noise changes faster than the recording-medium integration-time and therefore is not recorded. This system does not require a reference-wave coherent with the image, and it operates in real time. Experimental results through a simulated scattering medium demonstrate the contrast improvement over the conventional imaging arrangement.

Line narrowing and self frequency scanning of laser diode arrays coupled to a photorefractive oscillator

Line narrowing and self frequency scanning of a laser diode array coupled to a photorefractive passive-phase conjugate mirror has been demonstrated. Single-longitudinal mode operation is obtained and the coupling mechanism is discussed. >

Transient effects in four-wave mixing in photorefractive Passive Phase Conjugate Mirrors

Partial differential equations are set up and solved partly analytically, partly numerically for the spatial and temporal variation of the amplitudes and phases of the four beams participating in four-wave mixing in a linear Passive Phase Conjugate Mirror. The instantaneous frequency of the resonating beam is also determined. It is shown that the duration and main features of the transient regime are determined not only by the properties of the photorefractive crystal but also by the external optical circuit, in particular by the quality factor and detuning of the resonator.

Numerical solution of four-wave mixing in passive phase conjugate mirrors

An iterative method is used to find the solution for all the field amplitudes and for the detuning of oscillations arising in a linear passive phase conjugate mirror (PPCM). The effect of crystal absorption is included and both transmission and reflection gratings are investigated. In particular, it is shown that a PPCM can be realized with the aid of a BSO crystal in the presence of an applied electric field. >

Optical phase conjugation in nonresonant and saturable absorptive/resonant systems

Recent results obtained at Alabama A&M University on optical phase conjugation in electrically unpoled BaTiO3, BANANA and SBN crystals are presented. The decay curves of the transient gratings and phase conjugation in these crystals indicate the involvement of more than one exponential process, possible reasons for which are indicated. Self induced gratings have been studied in electrically unpoled SBN crystal using a He−Ne Laser. The oscillations in a ring passive phase conjugator (RPPC) and in a unidirectional ring resonator using an electrically poled BaTiO3 crystal have, been found to be bistable. It is also found that bistable oscillations are possible in a geometry in which the crystal is used simultaneously in a RPPC and as a linear passive phase conjugate (LPCC) mirror. The auxiliary oscillations pumped by the RPPC are bistable with the oscillations in LPCC. A brief review of the recent literature on phase conjugation in saturable absorptive/resonant systems along with the experiments planned to be undertaken by the authors on such systems are presented.

Coupling of diode laser arrays with photorefractive passive phase conjugate mirrors

An experimental study of the coupling of diode laser arrays to various photorefractive phase conjugate mirrors is presented. We demonstrate frequency locking of arrays as well as the control of their emitted light patterns.

Self-starting passive phase conjugate mirror with Ce-doped strontium barium niobate

We report the use of Ce-doped SrxBa1−xNb2O6, x=0.60 and 0.75, as the holographic four-wave mixing medium in the construction of a self-starting passive phase conjugate mirror using internal reflection. Without correcting for Fresnel reflections, a steady-state phase conjugate reflectivity of 25% was measured with Sr0.75Ba0.25Nb2O6:Ce. The distortion correcting property of such a mirror was demonstrated using an imaging experiment.

A novel technique for laser diode to single mode fiber coupling

Abstract An optical fiber coupler based on the semi-linear passive phase conjugate mirror is analyzed. The threshold coupling strength is determined from theoretical considerations. An estimate of 50% for the overall coupling efficiency is made, assuming there is good mode matching between the light incident on the fiber and the propagating mode. The coupler exhibits a high degree of alignment insensitivity allowing for simple manufacture.

Polarization recovery in phase conjugation by modal dispersal

We demonstrate scalar phase conjugation, i.e., one in which both transverse components of the incident beam are phase conjugated, which is achieved by tandem combination of a mode scrambling fiber and a photorefractive passive phase conjugate mirror.

Oscillation with photorefractive gain

We review theories and experimental demonstrations of oscillation with photorefractive gain. The unidirectional ring resonator; the linear passive phase conjugate mirror, a phase conjugate resonator (the semilinear passive phase conjugate mirror), and the double phase conjugate resonator are treated, the applications in path-length-to-frequency converting interferometers and one-way wavefront converters are described.

Beam coupling and locking of lasers using photorefractive four-wave mixing

We discuss the use of photorefractive four-wave mixing for coupling and locking of lasers. A demonstration of the double phase-conjugate mirror and the semilinear passive phase-conjugate mirror, pumped simultaneously by different lasers, is described. Cleanup of a distorted laser beam using another local laser and configurations for the phase locking of lasers are discussed.

Self-induced frequency scanning and distributed Bragg reflection in semiconductor lasers with phase-conjugate feedback

A GaAlAs semiconductor laser with feedback from a barium titanate photorefractive ring passive phase-conjugate mirror can be made to perform repeating or nonrepeating frequency scans over a 10-nm range toward either the blue or the red. The direction of scanning and whether the scans repeat may be controlled by adjusting the overlap of the interaction beams in the crystal. This overlap region may be adjusted so that the diode frequency spectrum, originally occupying about 10 longitudinal modes, scans and narrows as the conjugate signal builds up, coming to rest often in one, but sometimes two or three, longitudinal modes as a result of self-generated distributed-feedback effects. We also report similar effects caused by feedback from the total-internal-reflection passive phase conjugate mirror. The alignment-control mechanism of the ring mirror is, however, not available in this case.

Photorefractive oscillation with intracavity image and multimode fiber

A photorefractive oscillation between two cascaded passive phase conjugate mirrors (2C-PPCM) with intracavity phase and amplitude modulation and multimode fibers is described. The two semilinear PPCM’s operate via four wave mixing in BaTiO3 crystals. A single beam pumps only one PPCM and generates all other self-starting beams of the two PPCM’s

Coherent coupling of diode lasers by phase conjugation

We report experimental demonstrations of the use of a photorefractive barium titanate ring passive phase conjugate mirror in the coherent coupling of two GaAlAs diode lasers. By cooling the crystal towards its tetragonal to orthorhombic phase transition, we were also able to achieve infrared photorefractive phase conjugation with gain.

Plane-wave theory of nondegenerate oscillation in the linear photorefractive passive phase-conjugate mirror

We present a plane-wave theory of nondegenerate oscillation in the linear passive (self-pumped) phase-conjugate mirror (PPCM). The circumstances under which the plane-wave theory permits spontaneous nondegenerate oscillation in this and other PPCM's are discussed.