Quanzhong Jiang

Self-pumped phase conjugation of 18°-cut Ce-doped KNSBNcrystal at 632.8 nm

We report the self-pumped phase conjugation of an 18°-cut Ce-doped (KyNa1−y)2m(SrxBa1−x)1−m Nb2O6 crystal at a 632.8-nm He–Ne laser wavelength. A maximum phase-conjugation reflectivity of 84.3% has been measured. In addition, its incident angular response and time response are measured.

Study of two-wave coupling in Cu:KNSBN using red light

Abstract Two red-wave light mixing amplification in Cu:KNSBN is extensively studied through the gain versus the grating wavelength. The crystal has shown excellent response in the red region. The time evolution of the diffraction efficiency is also investigated.

Effects of Mn and Ti on microstructure and inclusions in weld metal of high strength low alloy steel

Abstract The influences of alloying elements on chemical composition of non-metallic inclusions, impact toughness and microstructure in weld metals of high strength low alloy steels have been studied. Results indicated that microstructure had changed from a mixture of acicular ferrite, proeutectoid ferrite, ferrite side plates and microphases to a mixture of acicular ferrite, bainite and microphases due to the addition of Mn and Ti. The impact toughness of weld metal was improved correspondingly. The volume fraction and composition of inclusions both influenced the proportion of acicular ferrite. Mn and Si based oxide globular inclusions located at the boundary of acicular ferrite plates in the weld metal produced using C–Mn–Si–Cu wire. When Mn and Ti were added to welding wires, the inclusions within acicular ferrite plates permitted fewer primary acicular ferrite plates to grow into relatively larger dimensions. Secondary acicular ferrites nucleating on pre-existing ferrite plates refined microstructure effectively.

Effects of inclusions on formation of acicular ferrite and propagation of crack in high strength low alloy steel weld metal

Abstract High strength low alloy steel was welded by gas shielded arc welding process without preheating. Microstructural characteristics of the weld metal, morphology of inclusions and crack propagation paths were investigated by means of optical microscopy and scanning electron microscopy. The chemical composition of the inclusion and element distribution across the inclusion were analysed via energy dispersive spectroscopy system. Results indicated relatively large inclusions with diameters of about 0·6–0·8 μm are much more effective in providing nucleation sites for acicular ferrite transformation and refining the microstructure within austenite grain than small ones with diameters of about 0·3–0·5 μm. When the main crack tip encountered inclusion, more crack paths would be initiated from the interface between inclusion and acicular ferrite plates.

Demonstration of self-pumped phase conjugation with laser beam incident to strontium barium niobate crystals from a negative c face

The self-pumped phase conjugation in strontium barium niobate (SBN) crystal is demonstrated by causing the laser beam to enter into the crystal from negative c face. Comparison is made between the experimental results and those obtained by the conventional configuration. The analysis and discussion are also presented.

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.

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.

Conjugation fidelity and multiple reflection waves in self-pumped phase conjugators with doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 crystals

Abstract The influence of four sets of multiple reflection waves from self-pumped phase conjugators with doped (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6 photorefractive crystals on the conjugation fidelity is analyzed in presence of pyroelectric effect and photovoltaic effect. Some proposals to improve the conjugation fidelity of a self-pumped phase conjugator are demonstrated. The multiple reflection waves and their dynamic features are observed and analyzed.

Real-time double-exposure interferometry using self-pumped conjugator with Cu: KNSBN

Abstract A simple real-time double-exposure interferometry employed by an internally self-pumped conjugator Cu: KNSBN is demonstrated. The device can perform a real-time nondestructive test of object.