CCD自动调光设计

介绍一种在89C51单片机的智能控制系统中,用A/D536等器件组成的真有效值电路作为CCD视频信号的检测电路,采取程序控制方式对天空背景下的目标进行自动调光控制.     

Linearized iterative method for determining effects of vessel attitude error on single-beacon localization

Single-beacon localization is an advanced (and relatively new) acoustic localization technique. The traditional single-beacon uses non-linear trajectories to localize underwater vessels, which has notable drawbacks in actual underwater operations. To mitigate the limitations associated with non-linear trajectories, we developed an innovative single-beacon localization with linear trajectories. The traditional linearized least square method is not suited to linear trajectories, so we developed a linearized iterative method that includes a virtual long baseline array to analyze the effects of vessel attitude error on single-beacon localization results. We simulated the forward velocity, number of beacons, distance measurement period, and vessel heading impact on horizontal localization. The results showed that according to the proposed analysis method, localization precision is strongly dependent on vessel attitude error.     

The coexistence of TE-TM surface waves in uniaxially anisotropic left-handed materials

We investigate theoretically the characteristics of surface waves in uniaxially anisotropic left-handed materials. The constraints for the existence of TE and TM polarized surface waves in uniaxially anisotropic left-handed materials are identified. We discuss mainly whether TE and TM polarized surface modes may coexist in the same frequency domain at the interface between one isotropic regular medium and another uniaxially anisotropic left-handed medium. It is shown that the answer to the coexistence of TE and TM surface modes is really positive. The Poynting vector and the density of energy associated with surface modes are calculated. Depending on the system parameters either TE or TM surface modes has the time averaged Poynting vector directed opposite or same to the mode phase velocity. In the presence of anisotropy, negative refraction does not need to be left-handed. We show that the characteristics of surface waves in uniaxially anisotropic left-handed media are significantly different from that in isotropic left-handed media.     

Development of an integrated optical system for warpage and hermeticity test of microdisplay

We have developed an integrated optical system to measure the warpage of a microdisplay product at post-packaging die-attach temperature and to test its hermeticity after manufacturing. This system is constructed based on the principle of Twyman/Green (T/G) interferometry and Newton interferometry. T/G interferometry is used to characterize warpage of the microdisplay's base-plate, while Newton interferometry is used to characterize the gap variance between face-plate and base-plate of the microdisplay. With these measurements, deformation and shape of the microdisplay can be comprehensively determined during its manufacturing process, which is critical for its quality test and reliability evaluation. Delicate mechanical system was designed to facilitate the optics integration and alignment. To evaluate the performance of the optical system itself, warpage of a sample was re-measured with Tailor–Hobson profilometer whose resolution is 10 nm, the results from these two testing systems agree well with each other. Some application examples of the integrated testing system were presented to verify its work efficiency.     

当前物理实验教学中创新误区的若干认识

本旨在通过对创新和创新教育的探讨，试图从思想上澄清人们对这一问题的认识。     

A photonic approach for microwave/millimeter-wave frequency measurement using stimulated brillouin scattering in single mode fiber

A photonic approach for microwave/millimeter-wave (MMW) frequency measurement is proposed and demonstrated based on stimulated Brillouin scattering (SBS) of a 20-km standard single mode fiber (SSMF). After the MMW signal is modulated to a laser source with two sidebands using optical carrier suppression (OCS) modulation, its frequency can be easily measured by monitoring the SBS-induced amplification with a power meter. Due to the 1-pm resolution of a tunable pump laser source, a frequency measurement range of 1–40 GHz is demonstrated in our experiment with a frequency resolution of 125 MHz. We believe the frequency measurement range can be further extended to satisfy photonic radar front-end processing application.     

微带型光导开关的电压转换效率

采用微带测试电路对光导开关电压转换效率进行了测试。依据传输线理论,考虑微带传输电路的端点反射,计算给出了光导开关导通电阻不为0的情况下,微带测试电路电压转换效率的解析结果。计算表明：对窄脉宽的线性电脉冲输出,电压转换效率将小于50%;对lock-on模式下的宽脉冲输出,电压转换效率可以超过50%,在理想情况下达到100%;在临界状态下,形成双峰电脉冲输出。结果表明,存在端点反射且光导开关产生电脉冲脉宽达到一定值时,微带线可以起到倍压传输线的作用。     

Defect structure and optical damage resistance of Hf:Fe:LiNbO3 crystals

A series of Hf:Fe:LiNbO₃ crystals were grown by the Czochralski technique with various doping concentrations of HfO₂. Their defect structures were analyzed by the UV-visible absorption spectra and infrared absorption spectra. The optical damage resistance of Hf:Fe:LiNbO₃ crystals was measured by the photo-induced birefringence change and the transmitted light spot distortion method. The results show that the optical damage resistance ability of Hf:Fe:LiNbO₃ crystals enhances remarkably with the HfO₂ concentration increasing when the HfO₂ concentration is lower than its threshold concentration (4 mol%). However, when the HfO₂ concentration exceeds its threshold concentration, the optical damage resistance ability of the crystals returns to decrease. This unusual behavior is explained by using the photovoltaic field produced in the crystals.     

Enhancement of photoluminescence intensity from Si nanodots using Al2O3 surface passivation layer grown by atomic layer deposition

Temperature-dependent photoluminescence (PL) from Si nanodots with Al₂O₃ surface passivation layers was studied. The Si nanodots were grown by low pressure chemical vapor deposition and the Al₂O₃ thin films were prepared by atomic layer deposition (ALD), respectively. The BOE (Buffer-Oxide-Etch) treatment resulted in the damaged surface of Si nanodots and thus caused dramatic reduction in the PL intensity. Significant enhancement of the PL intensity from Si nanodots after the deposition of Al₂O₃ thin films was observed over a wide temperature range, indicating the remarkable surface passivation effect to suppress the non-radiative recombination at the surface of Si nanodots. The results demonstrated that the Al₂O₃ surface passivation layers grown by ALD are effectually applicable to nanostructured silicon devices.     

Synthesis of glycoluril catalyzed by potassium hydroxide under ultrasound irradiation

Synthesis of the glycolurils catalyzed by potassium hydroxide was carried out in 17–75% yield at 40 °C in EtOH under ultrasound irradiation. Compared to the method using stirring, the main advantage of the present procedure is milder conditions and shorter reaction time.