Optical phase conjugation: principles, techniques, and applications

We report what is to our knowledge the first observation of mechanism transformation with wavelength of self-pumped phase conjugation (SPPC) BaTiO3:Ce crystals in the near infrared. in It was found that the SPPC mechanism changed from a backscattering and four-wave-mixing mechanism to a cat mechanism when the pump wavelength was varied from 706 to 770 nm. In addition, SPPC was obtained when the pump beam entered the crystal by the +c face, and a variation with wavelength of optical beam paths in the crystal was also observed.

Mechanism transformation with wavelength of self-pumped phase conjugation in BaTiO(3):Ce.

Self-pumped phase conjugation is generally believed to be attributed to degenerate four-wave mixing. Accordingly, the phenomenon requires the existence of three waves at certain interaction regions for the excitation of the fourth one. Although this condition is not satisfied by a train of femtosecond pulses with a repetition rate of 110 MHz, we have observed self-pumped conjugate pulses retroreflected by a BaTiO3 crystal. The conjugate character of the pulses is demonstrated with the distorter method.

Self-pumped phase conjugation with femtosecond pulses by use of batio3

Energy transfer characteristics of photorefractive contradirectional two-wave mixing

Potassium tantalite niobate (KTa1−xNbxO3, KTN) single crystals with various compositions and sizes were grown by double crucible Czochralski method in KTaO3–KNbO3 solid solution system. All the crystals we have grown are in good transparence and are >1 cm in size. Growth habit, morphological, structural and homogeneity properties of five different compositions of KTN crystals, including KTaO3, KTa0·91Nb0·09O3, KTa0·81Nb0·19O3, KTa0·75Nb0·25O3 and KTa0·63Nb0·37O3, are investigated in this work. Electron probe microanalysis shows that the composition fluctuation of KTN crystal is <0·0003 cm−1. X-ray diffraction experimental results show that all crystals belong to cubic phase at room temperature. Lattice parameters a are 3·984∼3·994 A, which corresponded to the composition of x = 0∼0·37. High resolution XRD measurement shows that all KTN crystals are in high integrity and good quality. Our work shows that the KTN crystals we have grown are in good quality and have a broad application prospects.

Growth of KTN crystals by double crucible Czochralski method

A new model is proposed to explain the origin of the self‐pumped phase conjugation (SPPC) that we have observed in KTa1−xNbxO3:Fe crystals. In this model SPPC is generated by both four‐wave mixing and backscattering processes rather than by only one of them. The advantage of this kind of phase conjugator is also discussed.

Qingcai Guan

Papers

Self‐pumped phase conjugation with a new mechanism in KTa1−xNbxO3:Fe crystals