Multimode interference (MMI) devices are widely used in planar lightwave circuit (PLC). The device length can be well reduced with tapered multimode region. Traditional design formula shows large error for MMI devices...Multimode interference (MMI) devices are widely used in planar lightwave circuit (PLC). The device length can be well reduced with tapered multimode region. Traditional design formula shows large error for MMI devices based on weakly- restricted waveguide. Based on the analysis with mode width as a substitution of waveguide width, a design formula with better precision was presented. Comparison with software simulation verified its exactness.展开更多
We present three families of one-soliton solutions for （2＋1）-dimensional Gross-Pitaevskii equation with both time-dependent scattering length and gain or loss in a harmonic trap. Then we investigate the dynamics of...We present three families of one-soliton solutions for （2＋1）-dimensional Gross-Pitaevskii equation with both time-dependent scattering length and gain or loss in a harmonic trap. Then we investigate the dynamics of these solitons in Bose-Einstein condensate8 （BECs） by some selected control functions. Our results show that the intensities of these solitons first increase rapidly to the condensation peak, then decay very slowly to the background; thus the lifetime of a bright soliton, a train of bright solitons and a dark soliton in BECs can be all greatly extended. Our results offer a useful method for observing matter-wave solitons in BECs in future experiments.展开更多
Photoluminescence (PL) polarization of a spin ensemble was examined over a wide excitation wavelength range from 520 nm to 700 nm and a temperature range from 3.5 K to 300 K after it transfers from a (AlGa)As barrier ...Photoluminescence (PL) polarization of a spin ensemble was examined over a wide excitation wavelength range from 520 nm to 700 nm and a temperature range from 3.5 K to 300 K after it transfers from a (AlGa)As barrier layer and eventually quenches irradiatively in a GaAs quantum well (QW).A highest PL circular polarization of 30% can be kept at temperatures up to 120 K,while its room temperature value reaches about 17%.It is found that the main features of the optical spin orientation in bulk Al 0.27 Ga 0.73 As materials can be reproduced in terms of the wavelength dependence of PL polarization degree,as the spin polarized ensemble transfers and relaxes into GaAs QW.The transient of PL polarization degree also indicates that a dense spin ensemble collected from the barrier region is in favor of conserving its polarization in GaAs QW as evidenced by a rising temporal response.展开更多
The authors present a new design of high resolution and wide dynamic range photonic crystal pressure sensor. This sensor is based on two-dimensional photonic crystal with square array of silicon rods surrounded by air...The authors present a new design of high resolution and wide dynamic range photonic crystal pressure sensor. This sensor is based on two-dimensional photonic crystal with square array of silicon rods surrounded by air. The sensor consists of a photonic crystal waveguide which is coupled to a photonic crystal nanocavity. The waveguide is configured by removing one row of Si rods and nanocavity is formed by modifying the radius of one Si rod. The sensor is designed for 1300 nm-1400 nm wavelengths. Simulation results show that resonant wavelength of nanocavity is linearly shifted to larger wavelengths by increasing the pressure. The designed sensor has a linear behavior between 0.1 GPa to 10 GPa of applied pressure and 8 nrrdGPa of pressure sensitivity.展开更多
文摘Multimode interference (MMI) devices are widely used in planar lightwave circuit (PLC). The device length can be well reduced with tapered multimode region. Traditional design formula shows large error for MMI devices based on weakly- restricted waveguide. Based on the analysis with mode width as a substitution of waveguide width, a design formula with better precision was presented. Comparison with software simulation verified its exactness.
基金Supported by NSFC under Grant Nos. 11041003, 10735030, 10874235, 10934010, 60978019, the NKBRSFC under Grant Nos. 2009CB930701, 2010CB922904, and 2011CB921500Zhejiang Provincial NSF under Grant No. Y6090592+1 种基金Ningbo Natural Science Foundation under Grant Nos. 2010A610095, 2010A610103, and 2009B21003K.C. Wong Magna Fund in Ningbo University
文摘We present three families of one-soliton solutions for （2＋1）-dimensional Gross-Pitaevskii equation with both time-dependent scattering length and gain or loss in a harmonic trap. Then we investigate the dynamics of these solitons in Bose-Einstein condensate8 （BECs） by some selected control functions. Our results show that the intensities of these solitons first increase rapidly to the condensation peak, then decay very slowly to the background; thus the lifetime of a bright soliton, a train of bright solitons and a dark soliton in BECs can be all greatly extended. Our results offer a useful method for observing matter-wave solitons in BECs in future experiments.
基金supported by the National Basic Research Program of China (Grant Nos.2007CB924904 and 2011CB932901)
文摘Photoluminescence (PL) polarization of a spin ensemble was examined over a wide excitation wavelength range from 520 nm to 700 nm and a temperature range from 3.5 K to 300 K after it transfers from a (AlGa)As barrier layer and eventually quenches irradiatively in a GaAs quantum well (QW).A highest PL circular polarization of 30% can be kept at temperatures up to 120 K,while its room temperature value reaches about 17%.It is found that the main features of the optical spin orientation in bulk Al 0.27 Ga 0.73 As materials can be reproduced in terms of the wavelength dependence of PL polarization degree,as the spin polarized ensemble transfers and relaxes into GaAs QW.The transient of PL polarization degree also indicates that a dense spin ensemble collected from the barrier region is in favor of conserving its polarization in GaAs QW as evidenced by a rising temporal response.
文摘The authors present a new design of high resolution and wide dynamic range photonic crystal pressure sensor. This sensor is based on two-dimensional photonic crystal with square array of silicon rods surrounded by air. The sensor consists of a photonic crystal waveguide which is coupled to a photonic crystal nanocavity. The waveguide is configured by removing one row of Si rods and nanocavity is formed by modifying the radius of one Si rod. The sensor is designed for 1300 nm-1400 nm wavelengths. Simulation results show that resonant wavelength of nanocavity is linearly shifted to larger wavelengths by increasing the pressure. The designed sensor has a linear behavior between 0.1 GPa to 10 GPa of applied pressure and 8 nrrdGPa of pressure sensitivity.
