Jianru Han

Dielectric and ferroelectric properties of (Na0.8K0.2)0.5Bi0.5TiO3 thin films prepared by metalorganic solution deposition

(Na0.8K0.2)0.5Bi0.5TiO3 thin films have been prepared on Pt∕TiO2∕SiO2∕Si and p-type Si substrates using a metalorganic solution deposition method. The films annealed at 700 °C crystallize well and present perovskite phase. The films exhibit a well-defined hysteresis loop at an applied voltage of 4 V, with a remanent polarization of 4.7μC∕cm2 and a coercive field of 38kV∕cm. The films also show fatigue-free response up to 1.5×1010 switching cycles. The relaxor behavior of the films is confirmed by the frequency-dependence of capacitance-temperature relation. The capacitance-voltage curves show that the films are polarization-type switching and the memory window is about 2.5 V at ±4V applied dc bias voltages. The changes of dielectric constant and dissipation factor with frequency are also investigated briefly.

Flux growth and properties of RbTiOAsO4 (RTA) crystals

Abstract Flux growth of RbTiOAsO 4 (RTA) crystal is reported. The unit cell parameters are determined as a = 13.2428 A, b = 10.7624 A and c = 6.6685 A. The transmission spectra range is 0.38 to 5.1 μ . The refractive indices at the various wavelengths and the nonlinear optical coefficients are measured. The phase matching curve for 1.064 μ laser is calculated.

Yellow laser potential at 585 nm of monoclinic GdCa4O(BO3)3 :Dy crystal

GdCa 4 O(BO 3 ) 3 : Dy (GdCOB : Dy) crystal was grown using Czochralski (CZ) pulling method. The polarized absorption and fluorescence spectra were measured at room temperature. The energy levels of Dy 3+ in the GdCOB : Dy crystal were given based on the spectra. The characteristic parameters of the GdCOB : Dy crystal were calculated using the Judd-Ofelt theory.

Growth and properties of (Cr3+, Nd3+) doped GdCa4O(BO3)3 crystals

Abstract Optical quality Nd:GdCa 4 O(BO 3 ) 3 (Nd:GdCOB) crystal and chromium sensitized crystal of Cr:Nd:GdCa 4 O(BO 3 ) 3 (Cr:Nd:GdCOB) were grown by the Czochralski (CZ) method. The transmittance spectra was measured at room temperature on 7at%Nd:GdCOB and lat%Cr:7at%Nd:GdCOB samples. The absorption in the blue-UV region of Cr:Nd:GdCOB was larger than that of Nd:GdCOB, which matched the xenon flash lamp very well. A 3×3×10mm 3 Nd:GdCOB sample without any antireflective coating was sidepumped using a pulsed dye-laser tuned to 595.4nm. The green-light output energy was 1.35mJ at a pump energy of 17.5mJ. The conversion efficiency was 7.7%, and the threshold energy was less than 1.2mJ which are the best results up to now to our knowledge. 3×3×7mm 3 Nd:GdCOB and Cr:Nd:GdCOB samples without antireflective coatings were pumped using a flash pump source. The threshold for Cr:Nd:GdCOB was 0.9J while for Nd:GdCOB it was I.O.J. The output green light energy was 2.46mJ for Cr:Nd:GdCOB at a 10J flash pump energy and was 1.96mJ for Nd:GdCOB at the same pump energy, which clearly shows that Cr 3+ ions have the sensitizing effect on the Nd 3+ ions in Nd:GdCOB crystal.

Study on the second-harmonic-generation of GdCa4O(BO3)3 crystals along various phase-matching directions

In this paper, the theoretical calculations of deff of GdCa4O(BO3)3 (GdCOB) along various phase-matching (PM) directions are reported. It is shown that the maximum deff is out of the main planes and the deff in the range of (0<θ≤90, 90<φ≤180) are larger than that in the range of (0<θ≤90, 0≤φ≤90). The PM direction along (θ=66.8, φ=132.6) for GdCOB crystal has the largest deff. Second-harmonic-generation (SHG) experiments were performed on GdCOB crystal along various PM directions. The results show that in GdCOB crystal, the intracavity SHG conversion efficiency is 27.6% along the PM direction (θ=66.8, φ=132.6) which is larger than that along PM directions in XY and XZ main planes, which are in good agreement with the theoretical calculations. The continuous-wave (cw) green laser output power is 1.22 W when LD pump power is 10 W in the Nd:YVO4/GdCOB laser.

Suppression of dynamic instability and comparison of the response time in mutually pumped phase conjugators

The origin and the suppression of dynamic instability have been experimentally studied in mutually pumped phase conjugators when the two input beams are coherent. Experimental results show that the dynamic instability of the phase conjugation outputs arises from the competition among backscattering gratings, reflection gratings, and shared transmission gratings. The effect of the competition on the coupling channel is also presented. A simple method, the slight vibration of the experimental table is proposed. It can eliminate the dynamic instability. The response time is measured and fit for several kinds of discovered mutually pumped phase conjugators. We find that the bird-wing and sickle mutually pumped phase conjugators, which have one internal reflection, have a shorter response time. A possible explanation is suggested.

Synthesis, growth and doped properties of PbWO4 crystals

Abstract High purity polycrystalline PbWO4 (PWO) has been synthesized by a chemical method. Pure and doped PWO crystals were grown by using a Czochralski technique. Transmittance spectra, light yield and decay constants of the crystal were measured. The effect of PWO crystal quality and doped ions on its scintillating properties is discussed in this paper.

PREPARATION AND CHARACTERISTICS OF Sm-DOPED Bi2Ti2O7 THIN FILMS

Crack-free Sm-doped Bi2Ti2O7 (Sm:Bi2Ti2O7) thin films with a strong (111) orientation have been prepared on p-Si(111) by chemical solution deposition (CSD). The structural properties and crystallizations were studied by X-ray diffraction. The surface morphology and quality were examined using atomic force microscopy (AFM). The dielectric constant and loss factor at different frequencies were also evaluated at room temperature. Their insulation was studied, too. The films exhibit better insulating property than does the pure Bi2Ti2O7.

PHOTOREFRACTIVE PROPERTIES OF CU-DOPED (K0.5NA0.5)0.2(SR0.75BA0.25)0.9NB2O6 CRYSTALS WITH DIFFERENT DOPING LEVELS AND DIFFERENT DIMENSIONS

In this article, we studied the photorefractive properties of Cu-doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 (Cu:KNSBN) crystals with different doping levels. The properties include two-wave mixing and self-pumped phase conjugation, absorption properties, and the growth conditions as well. We also studied the effect of the dimensions on the photorefractive properties. The mechanism of Cu-doped KNSBN and the influence of the different sites occupied by Cu+ on photorefractive properties are also discussed. All the experimental results showed that doping levels have much effect on the photorefractive properties. The crystal with a higher doping level has a higher effective charge carrier density, a larger coupling coefficient, and a faster response rate, which is suitable for fast optical information processing. Dimension has much influence on the photorefractive properties. The thinner crystal with the same doping level has a larger coupling gain coefficient, and a shorter response time.

Systematic studies on photorefractive crystal growth and properties of Cu- and Mn-doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6

In this paper, photorefractive (PR) crystals of Cu and Mn- doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 were symmetrically studied. We reported the growth conditions, the absorption properties and the photorefractive properties including two wave mixing (TWM) and self-pumped phase conjugation (SPPC). The mechanism of Cu-doped KNSBN was referred briefly, and the influence of the different sites occupied by doping ions on PR properties was also discussed. All these results reveal that: (1) In Cu-doped KNSBN crystals, the photorefractive properties become better with the increase of the doping level, such as higher effective charge carrier density, larger coupling coefficient, faster response rate, higher SPPC reflectivity. (2) The thinner sample shows larger coupling gain coefficient, which is due to the light creep effect and beam fanning effect. The response time becomes shorter with the decrease of the thickness. (3) In Cu:KNSBN crystals, the coupling gain coefficient of TWM was obtained up to 35 cm-1. (4) In Cu:KNSBN and Mn:KNSBN samples, the SPPC reflectivity up to 73% have been obtained, respectively. (5) The C-site in the tungsten-bronze structure of KNSBN has an effect on the PR properties of the crystal. All these results show that doping in KNSBN is an effective method to improve the PR properties. The Cu-doped KNSBN crystal is a very promising photorefractive material.