Acoustic wave exhibits inherently different characters of propagation, excitation and coupling in phonon band-gap materials in which its elastic, piezoelectric constants are modulated in order of acoustic wavelength. ...Acoustic wave exhibits inherently different characters of propagation, excitation and coupling in phonon band-gap materials in which its elastic, piezoelectric constants are modulated in order of acoustic wavelength. These kinds of novel materials were exampled by phononic crystals with elastic constants modulation, acoustic superlattice and ionic-type phononic crystals with piezoelectric constants modulation. In this talk, phonic crystals were constructed with steel rods embedded in air. Negative refraction of acoustic wave was both experimentally and theoretically established in the phononic crystals. The propagation of acoustic wave in the crystals show acoustic band structures because the waves are strong scattered at the Brillouin Zone Boundaries, analogy to electron band structure in real crystals and photonic band structure in photonic crystals. In the acoustic superlattice, ultrasonic waves could be excited by applied alternative electric fields by piezoelectric effect. The frequency, mode and amplitude of the excited wave are determined by the microstructured parameters of the acoustic superlattice at the condition of phase matching. Ionic-type phononic crystals describe the coupling between superlattice phonon and electromagnetic wave. The coupling process resulted in the polariton with a dispersion relation totally different from that of both superlattice phonon and E-M waves, analogy to the polariton of the ionic crystals but in microwave instead of infrared light. These microstructural dielectric materials show artificial abnormal properties and will find novel application in ultrasonic devices and microwave devices.展开更多
Simultaneous red and blue light generation in an LiTaO_(3) crystal with a double grating structure is first reported.The double grating consists of two separate domain reversal sequences(superlattices)in series and is...Simultaneous red and blue light generation in an LiTaO_(3) crystal with a double grating structure is first reported.The double grating consists of two separate domain reversal sequences(superlattices)in series and is fabricated by field poling technique at room temperature.Using a picosecond 532 nm laser as a pump source,the red light at 631 nm and blue light at 460 nm are generated at the same time.A possible application of the superlattice crystal is presented.展开更多
Experimental observation of optical bistability in a nonlinear two-dimensional volume refractive index grating is reported.The index grating in LiNbO_(3):0.1 wt.%Fe photorefractive single crystal was fabricated by usi...Experimental observation of optical bistability in a nonlinear two-dimensional volume refractive index grating is reported.The index grating in LiNbO_(3):0.1 wt.%Fe photorefractive single crystal was fabricated by using hologram recording and subsequent thermal fixing techniques.Due to the thermal fixing,the stored 2D volume index grating shows no optical erasure during readout.An explanation of the nonlinear phenomena is also given in terms of the intensity-enhanced bulk photovoltaic effects in LiNbO_(3):Fe material.展开更多
Direct observation of the domain-in-verted regions in LiNbO_(3) formed by proton exchange followed by heat treatment is performed by using transmission electron microscopy.A charged straight 180°tivinning domain ...Direct observation of the domain-in-verted regions in LiNbO_(3) formed by proton exchange followed by heat treatment is performed by using transmission electron microscopy.A charged straight 180°tivinning domain boundary was revealed and compared with winding domain boundaries in LiNbO_(3) grown by Czochralski method.Obtained results are significant to studying the mechanism of domain inversion and morphology of inversion domains.展开更多
文摘Acoustic wave exhibits inherently different characters of propagation, excitation and coupling in phonon band-gap materials in which its elastic, piezoelectric constants are modulated in order of acoustic wavelength. These kinds of novel materials were exampled by phononic crystals with elastic constants modulation, acoustic superlattice and ionic-type phononic crystals with piezoelectric constants modulation. In this talk, phonic crystals were constructed with steel rods embedded in air. Negative refraction of acoustic wave was both experimentally and theoretically established in the phononic crystals. The propagation of acoustic wave in the crystals show acoustic band structures because the waves are strong scattered at the Brillouin Zone Boundaries, analogy to electron band structure in real crystals and photonic band structure in photonic crystals. In the acoustic superlattice, ultrasonic waves could be excited by applied alternative electric fields by piezoelectric effect. The frequency, mode and amplitude of the excited wave are determined by the microstructured parameters of the acoustic superlattice at the condition of phase matching. Ionic-type phononic crystals describe the coupling between superlattice phonon and electromagnetic wave. The coupling process resulted in the polariton with a dispersion relation totally different from that of both superlattice phonon and E-M waves, analogy to the polariton of the ionic crystals but in microwave instead of infrared light. These microstructural dielectric materials show artificial abnormal properties and will find novel application in ultrasonic devices and microwave devices.
基金Supported by the State Key Program from the National Science and Technology Commission of Chinathe National Advanced Material Commit tee of China,and the National Natural Science Foundation of China under Grant No.69938010.S.N.Zhu is also grateful for the support from a mono-grant RFPP.
文摘Simultaneous red and blue light generation in an LiTaO_(3) crystal with a double grating structure is first reported.The double grating consists of two separate domain reversal sequences(superlattices)in series and is fabricated by field poling technique at room temperature.Using a picosecond 532 nm laser as a pump source,the red light at 631 nm and blue light at 460 nm are generated at the same time.A possible application of the superlattice crystal is presented.
基金Supported by the Grant for the Key Research Project in Climbing Program from the National Commission of Science and Technology of China.
文摘Experimental observation of optical bistability in a nonlinear two-dimensional volume refractive index grating is reported.The index grating in LiNbO_(3):0.1 wt.%Fe photorefractive single crystal was fabricated by using hologram recording and subsequent thermal fixing techniques.Due to the thermal fixing,the stored 2D volume index grating shows no optical erasure during readout.An explanation of the nonlinear phenomena is also given in terms of the intensity-enhanced bulk photovoltaic effects in LiNbO_(3):Fe material.
基金Supported by the Key Research Project in Climbing Program from the National Science and Technology Commission of China.
文摘Direct observation of the domain-in-verted regions in LiNbO_(3) formed by proton exchange followed by heat treatment is performed by using transmission electron microscopy.A charged straight 180°tivinning domain boundary was revealed and compared with winding domain boundaries in LiNbO_(3) grown by Czochralski method.Obtained results are significant to studying the mechanism of domain inversion and morphology of inversion domains.
