Photorefractive Phase Conjugate Mirror Research Articles

フォトリフラクティブ位相共役鏡を用いた高出力ピコ秒ホログラフィックレーザー

フォトリフラクティブ位相共役鏡を用いた高出力ピコ秒ホログラフィックレーザー

High Power, High Quality Phase Conjugate Vanadate Lasers

We presented high quality, high power pico-second output from a diode-side-pumped Nd: YVO4 laser system with a photorefractive phase conjugate mirror. Peak output powers in the range of 2.8-6.8MW were achieved at a pulse repetition frequency range of 0.33-1.0MHz. The corresponding average powers of 18-26W were obtained.

Power scaling of a pico-second Nd:YVO4master-oscillator power amplifier with a phase-conjugate mirror

We investigated design issues for the power scaling of a pico-second Nd:YVO(4) master-oscillator power amplifier system with a photorefractive phase-conjugate mirror by using standard beam propagation analysis. We also demonstrated a 25 W diffraction-limited pico-second output. A corresponding extraction efficiency of 31 % was achieved.

Over 10-watt pico-second diffraction-limited output from a Nd:YVO4 slab amplifier with a phase conjugate mirror

We have produced a high beam quality pico-second laser based on a continuous-wave diode pumped Nd:YVO4 slab amplifier with a photorefractive phase conjugate mirror. 12.8W diffraction-limited output with a pulse width of 8.7ps was obtained.

Multi-watt diffraction-limited picosecond pulses from a diode-pumped Nd:YVO4amplifier with a photorefractive phase conjugate mirror

We demonstrate>4 W and 7.2 ps output of a double-pass Nd:YVO4 slab amplifier with a photorefractive ring phase conjugate mirror. A double-pass gain of 190 and optical extraction efficiency of >20% were obtained. The amplified signal beam exhibits a TEM00 profile with beam propagation parameters Mx2<1.4 and My2<1.1.

Stabilization of the photorefractive double phase-conjugate mirror inBaTiO3

Photorefractive simple and double phase-conjugate mirrors very often exhibit strong instabilities in their reflectivities. One of their possible origins can be the competition between phase conjugation and its generating process, photorefractive beam fanning. However, by suitably choosing the incident beam widths and directions, we suppressed this competition and replaced it by the enhancement of each process by the other. This technique allows to obtain a double phase-conjugate mirror in BaTiO{sub 3} that establishes itself in seconds for beam intensities on the order of the tenth of a milliwatt. The reflectivities reached are on the order of 30% and stable within 3% for hours.

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%.

Photorefractive Materials and Their Applications. High Quality Output of a Broad-Stripe Laser Diode Using a Photorefractive Phase Conjugate Mirror.

A highly bright radiation from a single-stripe high power laser diode with a photorefractive phase conjugate mirror was presented. The laser diode was then operated in a narrow-band and generated a single-lobed far-field.

Photorefractive Materials and Their Applications. High-Power Nd:YAG laser Using Ring Self-Pumped Phase Conjugate Mirror.

A LD-pumped sigzag slab Nd:YAG oscillator-amplifier system using a photorefractive ring self-pumped phase conjugate mirror is developed. The photorefractive phase conjugator is optimized in the point view of high-energy pulse capacity, fidelity of phase conjugation and stability. The laser system generates the IR laser pulses of 600 mJ and the second harmonic pulses of 250 mJ at the repetition rate of 100 Hz. Both the IR and the second harmonic have 1.1 times diffraction limited beam quality.

Multi-watt CW output from a double-pass diode side-pumped Nd:YVO 4 amplifier with a Rh:BaTiO 3 phase conjugator

We demonstrate a 7.8 W high beam quality continuous-wave output of a double-pass Nd:YVO 4 slab amplifier with a photorefractive ring phase conjugate mirror. Optical extraction efficiency of 33% was obtained. Build-up time of the output of the amplifier was 10 s. Standard variance of the output power fluctuation was 2.6%.

High power solid-state laser with photorefractive phase conjugate mirror

High power solid-state laser with photorefractive phase conjugate mirror

Dynamics of Semiconductor Lasers with Optical Feedback from Photorefractive Phase Conjugate Mirror

The dynamics of semiconductor lasers with photorefractive phase conjugate optical feedback are experimentally studied. Photorefractive fringes considered here are rather static compared with time fluctuations of laser output power. Therefore, it is expected that a semiconductor laser with photorefractive feedback shows similar dynamics to those with conventional optical feedback. We examine relaxation oscillation and external cavity modes of laser output power in the presence of photorefractive phase conjugate feedback. It is proved that the dynamics of photorefractive phase conjugate feedback are fundamentally the same as those of conventional optical feedback.

Effect of reflection and 2K gratings on self-pumped phase-conjugate mirrors: theoretical and experimental studies

The effect of reflection and 2K gratings on the efficiency of photorefractive self-pumped phase-conjugate mirrors (SPPCM’s) was studied theoretically and experimentally. Semilinear SPPCM’s of BaTiO3 are used as an example. It is shown with numerical calculations that in normal experimental configurations all these gratings are helpful for the performance of the SPPCM’s. With a 45°-cut BaTiO3:Ce we determined experimentally the variation of reflectivity of a semilinear SPPCM when the crystal’s gain coefficients that correspond to the gratings were changed by variation of the cavity length of the semiresonator in the SPPCM. The experimental results verified the theoretical predications. The validity of our conclusions for SPPCM’s with other photorefractive crystals such as KTaxNb1-xO3 and (KyNa1-y)2Z(SrxBa1-x)1-ZNb2O6 is discussed.

Spatial shifts of the conjugate beam generated by a nondegenerate photorefractive phase-conjugate mirror

We demonstrate that the phase conjugation of a beam during nondegenerate four-wave mixing is accompanied by a spatial shift relative to the degenerate conjugate-beam location. Experiments with a photorefractive phase-conjugate mirror reveal that the phase-conjugate beam shifts have a nonmonotonic dependence on the probe's detuning frequency and comprise both lateral displacements of up to 218 mum and angular tilts of up to 34 arc sec. An approximate theory based on spatial dispersion coefficients is in partial agreement with the experimental results.

Tunable single-mode operation of a high-power laser-diode array by use of an external cavity with a grating and a photorefractive phase-conjugate mirror

We demonstrate a technique for tunable single-mode operation of high-power laser-diode arrays. A spatially filtered part of the far field from a gain-guided GaAlAs laser-diode array is directed to a diffractive grating and is coupled to a phase-conjugating self-pumped barium titanate crystal. The interaction among the grating, the dynamic gratings in the photorefractive crystal, and the spatial filter forces the laser-diode array with poor spatial and temporal coherence to oscillate in a single spatial and single longitudinal mode. At a drive current of two times the threshold, the array operates in a single-lobed far-field pattern that is only 1.5 times the diffraction limit. The bandwidth of the enhanced output beam is measured to be less than 0.03 nm, and the coherence length of the output is increased 45 times, to at least 16 mm. Once single-mode operation has been obtained, one can continuously tune the frequency over a range of 5 nm around a center wavelength of 811 nm by tilting the grating. More than 50% of the radiated energy of the free-running laser is coupled out of the system. The significantly enhanced coherence properties of the output may lead to a number of new or improved applications in areas such as second-harmonic generation, coupling into single-mode fiber, and pumping of solid-state lasers.

Suppressing self-induced frequency scanning of a phase conjugate diode laser array using counterbalance dispersion

Experimental results show that angular dispersion strongly influences the self-induced frequency scanning of a multimode broad-area diode laser array coupled to a photorefractive self-pumped phase conjugate mirror. Prisms or a dispersive grating placed in the external cavity opposing the material frequency dispersion of the phase conjugate BaTiO3 crystal suppress the frequency scanning and stabilize the center wavelength and the output power. We show that the dispersion of the crystal is crucial for the mechanism of the frequency scanning.

Laser-diode injection locking with a double phase-conjugate mirror in photorefractive Bi_12TiO_20 fiberlike crystal under external alternating voltage

Injection locking of two laser diodes operating at 681–684 nm with a double phase-conjugate mirror recorded in photorefractive Bi12TiO20 crystal under an external alternating electric field is studied. It was found that there are three different regimes of laser-diode coupling distinguished by the various coherences of the light emitted by the coupled laser diodes. The ability of the photorefractive double phase-conjugate mirror to recover the coherence length is experimentally demonstrated. Advantages of photorefractive Bi12TiO20 fiberlike samples over bulk BaTiO3 crystals to record the double phase-conjugate mirror are listed.

Reflectivity enhancement due to linear absorption in photorefractive phase-conjugate mirrors with depleted pumps

Using numerical simulations of the fully nonlinear equations that describe the steady-state optical fields that develop within photorefractive phase-conjugate mirrors, we have shown that the phase-conjugate reflectivity can be enhanced in the presence of linear absorption. Our investigations focused on the development of the optical fields that arise when the reflectivity is nonmonotonically dependent on the linear absorption both near and away from self-oscillation. We have identified several significant features associated with the enhancement. Near self-oscillation and with strong pumps, an increase in the loss can lead to a more efficient energy transfer to the probe by altering the phase of the coupling, resulting in an increase in the index grating amplitude. Away from self-oscillation and with strong pumps, the loss alters the distribution of the grating within the crystal, and maximum reflectivity is associated with an optimum distribution. Reflectivity enhancement that is due to linear absorption was shown to occur even in the weak-pump case, thus providing unequivocal evidence of the veracity of this phenomenon.

Modes of resonators with dispersive phase-conjugate mirrors

We investigate the transverse and longitudinal modes of a resonator consisting of a spherical mirror, a Gaussian aperture, and a dispersive phase-conjugate mirror (PCM). The photorefractive PCM introduces spatial dispersion in the form of lateral and focal shifts along with temporal dispersion. For both degenerate and nondegenerate operation, the decentered Gaussian beam was found to be a mode whose peak intensity is displaced from the resonator axis. In the nondegenerate case, the components of a mode oscillating at a pair of frequencies that are up and down shifted from the pump frequency by the same amount have different spatial distributions, so that the intensity pattern moves periodically across the output mirror. The resonance frequencies of the longitudinal modes are calculated numerically.

Nd:YAG master-oscillator power amplifier with a rhodium-doped BaTiO_3 self-pumped phase-conjugate mirror

We investigate Nd:YAG master-oscillator power amplifier arrangements with an infrared-sensitive rhodium-doped BaTiO(3) photorefractive phase-conjugate mirror. In these setups the phase-conjugate mirror is simple to implement, compact, passive, and completely self-contained. We demonstrate a reasonable extraction efficiency (~50%), response times in the range of several minutes with our experimental conditions and an excellent ability of the phase-conjugate mirror to compensate for severe phase aberrations.