Xuefeng Yue

Studies on self-pumped phase conjugation in Cu-doped (K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 crystals

The use of Cu-doped (K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 as self-pumped phase conjugators using internal reflection is reported. Reflectivities as high as 63% at 5145.5 nm and 60% at 632.8 nm were realized. It was found that the photorefractive response changes significantly at different doping concentration. The responses of the crystals to the laser wavelength, incident angle and dopant concentration are studied.

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 high reflectivity by stimulated forward- and backward-scattering tetragonal potassium tantalate niobate crystal

Abstract Self-pumped phase conjugation in tetragonal Fe-doped KTa 1− x Nb x O 3 crystal with a Q -switched, frequency-doubled Nd:YAG laser with power in the milliwatt range is demonstrated. A phase conjugate reflectivity as high as 55% was measured. Both stimulated forward- and backward-scattering were involved in the self-pumping process simultaneously. The coupling characteristics of this crystal are analyzed and compared with those of BaTiO 3 crystal.

Contradirectional two-wave mixing in a strontium barium niobate self-pumped phase-conjugate mirror.

Contradirectional two-wave mixing in the process of self-pumped phase conjugation is analyzed theoretically, and it is found that this coupling interaction can enhance or restrain the phase-conjugate reflectivity depending on the optical configuration. This analysis is used to explain the unusual experimental results that were obtained in a strontium barium niobate self-pumped phase conjugator.

Planar waveguide refractive index distribution functions determined precisely from mode indices

The inverse WKB (IWKB) approximation has been extended to derive the index distribution functions from the measured mode indices of a planar waveguide. Through the use of this technique, the forms of the index distribution functions are obtained by IWKB approximation and a criterion is used to derive the functions accurately. The results are compared to the exponential and Fermi distributions. It is shown that the index profile, surface index, and waveguide depth can be obtained more accurately than with the original IWKB approximation. Finally, the index distribution function of a c-cut proton-exchanged LiTaO(3) waveguide is given by this technique, the mode indices calculated with this function agree with the experimental results in the range of 10(-4).

Studies of the formation of self-pumped phase conjugation in a Cu-doped KNSBN crystal

Abstract The internal self-generated loop in a photorefractive Cu-doped KNSBN crystal and the nehavior of phase-conjugate beams during self-pumping have been studied experimentally. Their relations to the crystals coupling constant, dimension and experimental conditions were analyzed.

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.

Studies of a ring phase-conjugate mirror containing a photorefractive crystal with asymmetric transmission

The characteristics of the ring passive phase conjugator with a nonreciprocal transmission photorefractive crystal inside its loop are studied experimentally and theoretically. It is found that the orientation of the photorefractive crystal and the ratio of energy losses in the two sides of the crystal within the loop can combine to influence the phase-conjugate reflectivity of this device.

Self-pumped phase conjugation of KLTN crystal

Abstract Potassium lithium tantalate niobate (KLTN) crystals were grown using the flux pulling method. The two-wave mixing gain coefficient of a KLTN:Fe crystal was measured to be 2.7 cm −1 . Using this crystal, a “cat” self-pumped phase conjugator has been demonstrated, for the first time. A reflectivity of 14% and a response time of the phase conjugator of 3 s at 3 W/cm 2 was measured using a frequency-doubled Nd:YAG laser.

Photorefractive-crystal shape-parameter influence on formation of self-pumped phase conjugation

The influence of crystal-shape parameters on formation of self-pumped phase conjugation is studied experimentally. The parallelism of two c-cut faces of a barium strontium potassium niobate crystal of cuboid shape is changed to control the internal oscillation and thus to induce or to suppress the generation of self-pumped phase conjugation.