Noise performance of the high speed image sensor is a bottle neck for its low illumination applications. As the foremost stage circuit, pixel noise is an important portion of high speed image sensor system. This paper has discussed and analyzed the different noise source of the 4T pixel and influence on the image quality of high speed image sensor in detail. We proposed circuit model of pixel with ideal correlated double sampler to simulate the noise source distribution in the pixel and noise reducing methods. Pixel random readout noise can be effectively reduced to 5.44e by optimizing the gate size of the reset transistor.
The measurement and analysis of the microwave frequency response of semiconductor optical amplifiers (SOAs) are
proposed in this paper. The response is measured using a vector network analyzer. Then with the direct-subtracting
method, which is based on the definition of scattering parameters of optoelectronic devices, the responses of both the
optical signal source and the photodetector are eliminated, and the response of only the SOA is extracted. Some
characteristics of the responses can be observed: the responses are quasi-highpass; the gain increases with the bias
current; and the response becomes more gradient while the bias current is increasing. The multisectional model of an
SOA is then used to analyze the response theoretically. By deducing from the carrier rate equation of one section under
the steady state and the small-signal state, the expression of the frequency response is obtained. Then by iterating the
expression, the response of the whole SOA is simulated. The simulated results are in good agreement with the measured
on the three main characteristics, which are also explained by the deduced results. This proves the validity of the
GaAs/AlGaAs quantum dot arrays with different dot sizes made by different fabrication processes were studied in this work. In comparison with the reference quantum well, photoluminescence (PL) spectra from the samples at low temperature have demonstrated that PL peak positions shift to higher energy side due to quantization confinement effects and the blue-shift increases with decreasing dot size, PL linewidths are broadened and intensities are much reduced. It is also found that wet chemical etching after reactive ion etching can improve optical properties of the quantum dot arrays.