Optoelectric material and micro-system
2017, 46(1): 120001.
doi: 10.3788/IRLA201746.0120001
A new type of distributed sensor system based on Rayleigh scattering Brillouin Optical Time Domain Analysis (RBOTDA) was proposed. This system was realized in one end access fiber, which can improve the shortcomings of two end access in conventional BOTDA. Parallel structure with two EOM were used to generate pulsed light with continuous base wave. Probe light was provided by the Rayleigh scattering of the base continuous light. This avoids the interference of a variety of Stimulated Brillouin Scattering (SBS) effect and brings the higher signal to noise ratio and longer sensing distance. The dual sideband probe scheme turns the system to be highly robust against pump pulse depletion and non-local effect. The SBS function mechanism of the system was analyzed and the feasibility of the proposed method was demonstrated experimentally. The results show that the Brillouin gain spectra fit Lorenz Curve perfectly and non-local effect is suppressed effectively. The Brillouin frequency shift is 10.867 GHz and the Brillouin linewidth is about 40.21 MHz with 50 ns pulse width on the 2.4 km optical fiber at the temperature of 25℃.
2017, 46(1): 120002.
doi: 10.3788/IRLA201746.0120002
A CMOS image sensor with coupling capacitor based AC-coupled CTIA and digital CDS was proposed. By adding a coupling capacitor to the conventional CTIA circuit, the dark current of the photodiode was reduced via controlling the bias voltage of the photodiode; Meanwhile, an off-chip digital CDS was adopted to reduce the reset noise of the pixel and the FPN by realizing the subtraction algorithm between the reset signal and pixel signal after A/D conversion off-chip. This CMOS image sensor was implemented in the 0.35 m standard CMOS technology. The pixel array was 256256, and the pixel size was 16 m16 m. The experimental results show that the dark current can be minimized by reducing the bias of the photodiode nearby zero. The temporal noise and FPN are obviously reduced after adopting the off-chip digital CDS.
2017, 46(1): 120003.
doi: 10.3788/IRLA201746.0120003
The output power of terahertz resource is a critical parameter to limit the long range application of terahertz technology. To accomplish the high efficiency terahertz multiplier, two high-efficiency 170 GHz balanced doublers were built using the two planar Schottky diodes with diverse electrical specification. The employed equal circuit diode model, based on the developed high-frequency characteristic modeling, considered the IV characteristics, the limits drift velocity saturation of carries, DC series resistance and skin effect simultaneously. From the comparison and analysis of the simulated data, the impact of diode electrical parameter on the doubler performance was discussed. Test data show that the two 170 GHz balanced doublers show 11% and 24% highest efficiency respectively, 15 mW and 25 mW output power correspondingly across a 155-178 GHz band. As shown in measured result, the employed Schottky diode modeling and balance structure is suitable option to design high efficiency terahertz multiplier.
2017, 46(1): 120004.
doi: 10.3788/IRLA201746.0120004
Aimimg at the problem of the defects on the surface of components in infrared optical systems, the scattering characteristics of optical components surface under different levels of defects were analyzed quantitatively based on Mie scattering theory. The variation of the bidirectional scattering distribution function(BSDF) on the surface of the optical component was discussed, and then a scattering model of optical components under different levels of defects was established. On this basis, a Gemini telescope was taken as an example, and the self-generated thermal radiation flux and its distribution of the system on the image plane was simulated quantitatively by using the ASAP optical analysis software for the case of the primary mirror under different levels of defects. Furthermore, according to the definition of the effective emissivity, the quantitative evaluation of the stray radiation of the system was carried out. The results indicate that the optical component under different levels of defects not only alter the stray radiation flux and its radiation distribution of the system on the image plane, but also change its effective emissivity, the effective emissivity of the system is 2.19%, 2.34%, 2.46%, 2.59%, 2.72% and 3.08% respectively when primary mirror defect levels under six cases such as 0, I-10, I-20, I-30, II and III. Thus, the stray radiation performance of the system decreases with the increasing of the level of the defects. Consequently, the levels of defects on the surface of the optical component should be strictly controlled in the practical applications.
2017, 46(1): 120005.
The crosstalk between the pixel units is the key parameter for the imaging quality of CMOS array detector. The mathematical analysis model of the electrical crosstalk was established in order to explore the influence of different light sources on the electrical crosstalk of CMOS. Furthermore, the characteristics of electrical crosstalk under the illumination of monochromatic light and broadband sources were also numerically simulated. The results show that, the electrical crosstalk increases with the increase of the wavelength of monochromatic light, as well as the spectrum bandwidth and the center wavelength of broadband sources. Moreover, the impact of broadband sources on the electrical crosstalk is greater than monochromatic light when their center wavelengths are the same. The electrical crosstalk for the monochromatic light with the radiation power of 600 W and the wavelength of 1 064 nm is about 50.611 mV, and the electrical crosstalk for broadband source with the spectrum bandwidth of 400 nm is about 50.914 mV in the same radiation power and wavelength. Consequently, the electrical crosstalk of broadband source increased by about 0.303 mV compared to the monochromatic light.
