Study on photorefractive effect in KTiOPO4 waveguides

Abstract

Photorefractive effects (PRE) in KTiOPO4 channel waveguides were studied at the wavelengths 0.633 and 0.83 μm. The 4 μm-wide waveguides were fabricated by Rb ion exchange on the z-face of the crystals and along the y axis. At 0.633 μm, crystals from one source showed conventional photorefractive response with a saturation index change Δn of 2×10−5, but samples from a different source were not photorefractive. Neither type of crystals displayed photorefractive behavior in response to 0.83 μm light at guided-wave power flow of 2.4×107 W/m2. Differences in bicrystal structure are suggested as a possible cause of differing PRE between the two samples. On crystals from the first source, the relaxation time of generating PRE is related to power flow of the irradiating beam. The relaxation time of PRE disappearance after stop irradiation is also related to power flow of the irradiating light.

Strong self- and cross-phase modulation effects in chromium-doped KTiOPO4 crystals

“…Several authors reported in the past on spatial modulation of a laser beam in KTP. [15][16][17] In those experiments the buildup of a space-charge field and an electro-optic effect in KTP has been identified as the source of refractive index modulation. This photorefractive effect in KTP has been shown to be extremely anisotropic because of the anisotropy in the ionic conductivities along and perpendicular to the z axis of the crystal ͑10 Ϫ8 and 10 Ϫ12 ⍀ Ϫ1 cm Ϫ1 , respectively͒.…”

“…This photorefractive effect in KTP has been shown to be extremely anisotropic because of the anisotropy in the ionic conductivities along and perpendicular to the z axis of the crystal ͑10 Ϫ8 and 10 Ϫ12 ⍀ Ϫ1 cm Ϫ1 , respectively͒. 15 Moreover, the typical times needed to observe self-induced effects ranged from several minutes 16 to many hours 17 ͑compare with 4 ms observed in Cr:KTP͒. In addition, even at laser powers much higher than those applied in our experiments the refractive index has changed considerably less than in Cr:KTP.…”

Ion-exchanged Fe doped KTiOPO4 optical waveguides

“…6 Recently it was found that the photorefractive effect ͑PRE͒ is different for two different kinds of KTP crystals. 7 At 0.633 m, crystals from one source have conventional photorefractive response with a saturation index change of 2ϫ10 Ϫ5 , but samples from a different source do not exhibit photorefractive effect. The reason for this difference is not well understood, and impurities might be one of the reasons.…”