Xiaodong Mu

High reflectivity self‐pumped phase conjugation in an unusually cut Fe‐doped KTa1−xNbxO3 crystal

In this letter, a new type of self‐pumped phase conjugation (SPPC) is demonstrated and a phase conjugate reflectivity as high as 83.8% is measured in an unusually cut Fe‐doped KTa1−xNbxO3 (KTN:Fe) crystal with a He‐Ne laser. Some novel characteristics of this type of device are found, which may reduce the need for special crystal qualities to obtain SPPC. Finally, a possible mechanism is postulated to reasonably explain this type of SPPC.

Self-pumped phase conjugation with mechanism transformation in potassium sodium strontium barium niobate

Both multistage and a great number of four-wave mixing interaction region models arising from contradirectional two-wave mixing to generate phase conjugation beam are suggested for the first time to our knowledge with a beam entering negative c face of the crystal. The mechanism transformation with geometric parameters is also observed and discussed. The backscattering beams from random noise beams may be expected to be amplified by contradirectional two-wave mixing under the beam entering negative c face of copper-doped potassium sodium strontium barium niobate. The maximum of reflectivity attains 33%.

Energy transfer characteristics of photorefractive contradirectional two-wave mixing

Abstract Expressions of the coupling constant for contradirectional two-wave mixing (CTWM) have been derived. The calculations show that the energy transfer in CTWM has some unique characteristics different from the forward two-wave mixing (FTWM), in which the energy transfer direction is dependent on the two beam orientations with respect to the crystal polar axis and the sign of the light-induced carriers as well as the electro-optic coefficients. As a result, the CTWM can have a reverse energy transfer direction to the FTWM under a certain condition. The experimental results in two typical crystals of Rh-doped BaTiO3 and in Ce-doped strontium barium niobate (SBN:Ce) demonstrate the theoretical investigations very well.

CONTRADIRECTIONAL TWO-WAVE MIXING IN RH-DOPED BATIO3 CRYSTAL

Contradirectional two-wave mixing (CTWM) in Rh-doped BaTiO3 crystal is investigated. The experimental results show that the energy transfer of CTWM has some distinctive characteristics different from forward two-wave mixing. Theoretical analysis of CTWM is presented in good agreement with the experimental observations. Both the experimental and theoretical studies show that the energy transfer direction of CTWM depends not only on the orientation of the crystal c axis and the sign of the light-induced carriers, but also on the electro-optic coefficients.

Study on self‐built optical path production in Ce‐doped BaTiO3 stimulated photorefractive scattering self‐pumped phase conjugator

The observations on the stimulated photorefractive scattering self‐pumped phase conjugator (SPS‐SPPC) in Ce‐doped BaTiO3 demonstrate that the self‐built pumped paths in the SPS‐SPPC are induced by the scattering seeds. Using these results, a formation mechanism of the SPS‐SPPC is presented, which is related to the scattering seeds, the contradirectional two‐wave mixing, and four‐wave mixing. The production conditions of the pumped paths are also given. The studies show that both too short and too long distances from the scattering seed to the region of the four‐wave mixing will bring about a failure in building the optical paths, and the large backscattering coefficient is always advantageous to produce these paths.

Enhancement of the response rate of internal reflection self‐pumped phase conjugators with Ce‐ and Mn‐doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 crystals using intermittent light

Dramatic enhancement of the response rate of internal reflection self‐pumped phase conjugators with Ce‐ and Mn‐doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 crystals is observed with an intermittent laser beam as the pumping beam. Analysis that involves charge carrier migration driven by a photoinduced electric field is given.

Sickle mutually pumped phase-conjugate mirror : Theoretic and experimental demonstration

A new mutually pumped phase conjugator with a photorefractive copper-doped potassium sodium strontium barium niobate crystal is demonstrated, in which the beams travel along a geometric path similar to the outline of a sickle. The maximum reflectivity is as high as 168%. Phase-conjugate images are obtained. The two-interaction region theory, based on the coupled plane wave amplitude, is used to account for the main characteristics of the new phase conjugator. The threshold coupling strength which depends on the reflection loss and the incident beam ratio, is also investigated and calculated.

Temperature dependence of photorefractive properties of a Cu-doped barium strontium potassium sodium niobate crystal

Abstract The gain of forward two-wave mixing (FTWM) and time response of a Cu-doped barium strontium potassium sodium niobate (KNSBN) crystal are investigated at 514.5 nm in the temperature range 20–120°C. It is found that the gain reaches its maximum value at about 90°C. The effective photorefractive charge density decreases with temperature. The response and erasure rates increase with increasing temperature. Moreover, the erasure process can be described by a diexponential function. A band diagram of the two-center charge transport model is presented. The phenomena are explained qualitatively.

Observation of multireflections from cat self-pumped phase conjugators with Cu-doped (K 0.5 Na 0.5 ) 0.2 (Sr 0.75 Ba 0.25 ) 0.9 Nb 2 O 6 crystals and conjugation fidelity analysis.

Four sets of multireflection orders from cat self-pumped phase conjugators of Cu-doped (K0.5Na0.5)0.2 (Sr0.75Ba0.25)0.9Nb2O6 (Cu:KNSBN) crystals are reported for the first time to our knowledge. The novel phenomenon of transient pulsation of the multireflection orders is observed and analyzed. The nonconjugate part accompanying the returning phase-conjugate beam is observed in the cat self-pumped phase conjugators of Cu:KNSBN and is analyzed by multireflections and two-wave mixing.

Asymmetric transmission device using Fe-doped KTaxNb 1–x O 3 crystal

A new type of asymmetric optical transmission device based on contradirectional two-wave mixing between an incident beam and its backward-scattering beams in Fe-doped KTa(x)Nb(1-x)O(3) crystal is demonstrated. The transmittance ratio of the beams propagating in opposite directions can be adjusted by a change in the angle between the incident beam and the c axis; the maximum ratio is nearly 50:1 at only one incident beam. Approximate solutions of two opposite transmittances are derived and discussed. It is possible to use this device as an optical isolator or an optical diode.