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Yang T.,Tianjin University | Yang T.,Key Laboratory of Optoelectronic Information Technology | Niu X.,Tianjin University | Niu X.,Key Laboratory of Optoelectronic Information Technology | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The generation of terahertz (THz) pulses based on optical rectification effects in GaAs has become more and more attractive and practical due to advances in high power ultrashort pulse fiber lasers. Normally coherence length is a parameter introduced for judging how the phases match by comparing the group velocity of optical pulses with the phase velocity of one of frequency components, like, for example, a component at 2 THz, of THz pulses. It is shown in this paper that the coherence length can not characterize the THz pulse generating process well because it can not count the contribution of all components in the spectrum band of the THz pulses. An energy conversion efficiency calculation model is proposed in this paper by integrating the energy of all THz components generated in the optical rectification process in a planar waveguide device. Based on the calculation model, the evolution of a THz pulse along the longitudinal direction of the waveguide is simulated and the results are used for design of the optimal waveguide structure for which the highest energy conversion efficiency could be reached to 1.5 × 10 -3. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE). Source


Yang T.,Tianjin University | Yang T.,Key Laboratory of Optoelectronic Information Technology | Qiu C.,Tianjin University | Qiu C.,Key Laboratory of Optoelectronic Information Technology | And 8 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

High resolution wavelength-tunable lasers are essential to sensing applications. For sensing applications, high resolution is needed to improve the spatial resolution and/or measurement accuracy, and fast tuning (sweeping) is required to enhance the measurement speed for dynamic sensing. However the demand of high resolution conflicts with the requirement of fast continuous wavelength tuning. The solution to this issue is tuning the wavelength of the output in a quasi-continuous way in which the length of each step is dependent on the frequency of a RF generator which is used to drive a single-sideband (SSB) modulator in the wavelength-swept optical system. In this paper, a principle of the step-tunable wavelength-swept optical system is proposed and demonstrated. The two optical features of narrow bandwidth and fairly high optical output power make the system unique for improving the accuracy of the measurement of the center-wavelength of a fiber Bragg grating (FBG) sensor. In addition, changing the tuning-step by adjusting the frequency of a RF generator electrically is user-friendly compared to the conventional wavelength swept systems by tuning optical elements mechanically. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE). Source


Zhang Y.,Tianjin University | Zhang Y.,Key Laboratory of Optoelectronic Information Technology | Yang T.,Tianjin University | Yang T.,Key Laboratory of Optoelectronic Information Technology | And 8 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Light detection and ranging (lidar) is used for various applications such as remote sensing, altimetry and imaging. Continuous wave frequency modulated (CWFM) lidars rely on linearly ramping the optical frequency of a laser and interfering the delayed echo signal with a reference signal to produce a beat frequency. The range resolution of lidar is determined by the swept frequency range of the linearly chirped continuous light waves in a frequency modulation system. For example, for 1mm range resolution, it needs the frequency sweep range of more than 150 GHz. In this paper a system which can generate a linearly chirped optical waveform within a super broad-wide band of 200 GHz, using cascaded phase modulators (PM) and single side band (SSB) modulator, is designed as a light source in a high resolution lidar system. © 2015 SPIE. Source


Zhang C.,Key Laboratory of Optoelectronic Information Technology | Ao J.-P.,Key Laboratory of Optoelectronic Information Technology | Wang L.,Key Laboratory of Optoelectronic Information Technology | Jiang T.,Key Laboratory of Optoelectronic Information Technology | And 4 more authors.
Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica | Year: 2012

We investigate the electrodeposition of gallium metallic precursor on gallium and Cu/In substrates from acidic aqueous solutions. The effect of the supporting electrolyte and the solution pH value for the electrodeposition of Ga is investigated by cyclic voltammetry. During Ga electrodeposition, gallium gradually diffuses into the film, and reacts with CuIn alloy to produce CuGa2 at the Cu/In interface. We use triethanolamine to protect the Cu/In and Ga films from being oxidized, and thus this improves the current efficiency of Ga-electrodeposition. The Cu-In-Ga films are annealed in an Se atmosphere to produce Cu(In 1-xGa x)Se 2(CIGS) thin films with high quality, and the efficiency of the solar cell prepared using these films is 9.42%. © Editorial office of Acta Physico-Chimica Sinica. Source

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