Showing papers on "Noise (radio) published in 2022"

Evolution of Low-Noise Avalanche Photodetectors

Abstract: This paper reviews materials and structural approaches that have been developed to reduce the excess noise in avalanche photodiodes and increase the gain-bandwidth product.

Highly precise measurement of atmospheric N2O and CO using improved White cell and RF current perturbation

Abstract: A highly precise dual gas sensor for measurement of atmospheric nitrous oxide (N2O) and carbon monoxide (CO) was developed and evaluated. A room temperature interband cascade laser emitting at 4.54 μm was used as a laser source to cover the absorption lines of N2O and CO simultaneously. Sensitivity and precision were enhanced by using an improved White cell with 76 m effective optical path length and radio frequency noise perturbation technique to reduce optical interference noise. A method was proposed to correct the laser frequency by calculating the correlation coefficient between the absorption signal with the reference signal, which effectively reduced the long-term drift of the absorption line center to less than 4 × 10−5 cm−1. By further precisely control the temperature and pressure of the absorption cell, a continuous 24 h measurement precision of 65 ppt N2O and 133 ppt CO at 0.1 Hz was demonstrated, with a daily drift less than 1.5 ppt. Finally, the repeatability and reliability of the sensor system were validated by real atmospheric measurements for two consecutive days.

320×256 Extended Wavelength In x Ga 1-x As/InP Focal Plane Arrays: Dislocation Defect, Dark Signal and Noise

Abstract: In0.75Ga0.25As and In0.83Ga0.17As 320×256 short-wave infrared focal plane arrays (SWIR FPAs) with pixel pitches of 24 and 30 μm, extended cutoff wavelengths of 2.2 and 2.5 μm, low dark current densities of 5.2 and 21 nA/cm2, and high peak detectivities of 6×1011 and 6×1012 cmHz1/2W−1 are attained at 180 K, respectively. Lower 1/f noises and smaller knee frequencies are observed for the 2.2 μm FPA, indicates the dislocation defect-related trap states act as the major contributor for the 1/f noise. The non-uniformities of the dark signal and the dark noise are roughly the same for both FPAs at a short integration time of 1 ms (29% and 25% at 180 K, respectively) whereas are much smaller for the 2.2 μm FPA at longer integration times. Moreover, the dark current shot noise dominant integration time ranges are determined to be >20 and >2 ms for the 2.2 and 2.5 μm FPAs, respectively. Enhanced heat signature recording capability is also observed for wider SWIR spectral range while more effective suppression routes of dislocation defect must be incorporated for further improved sensitivity.

Stabilized Long-Distance Superluminal Propagation Based on Polarization-Matched Low-Noise Brillouin Lasing Resonance

Abstract: This paper comprehensively investigated noise characteristics of superluminal propagation based on low-noise single-frequency Brillouin lasing oscillation with the aid of a population inversion dynamic grating. Thanks to high-degree polarization alignment between the Brillouin pump and the lased Stokes lightwaves in polarization maintaining fibers, efficient Brillouin lasing resonance with over 10-dB relative intensity noise suppression has been demonstrated to activate Brillouin loss-induced anomalous dispersion in the vicinity of pump signals, benefiting a noise-insensitive superluminal propagation along kilometer-long optical fibers with robust resistance to ambient disturbance. Consequently, sinusoidally modulated pump signals experienced the time advancement of 4634.0 ns at the group velocity of 10.63 c . Results show that the variance of the fractional advancement with polarization maintaining fibers is 2.54 × 10−4 which is two orders of magnitude lower than that of conventional single mode fibers. Furthermore, the dependence of the group velocity on the modulation frequency was experimentally investigated, showing good agreement with the theoretical analysis.

DC and Noise Performance of Si IMPATT Oscillator at Ka Band

Abstract: In this present article, DC and noise simulation is accomplished on 1-D model of Si IMPATTs at Ka band. The simulated outcomes from the present method are in close agreement with experimental one.

Contribution of microchannel plate luminescence to the noise of 20-inch photomultiplier tubes

Abstract: Since microchannel plate (MCP) photomultiplier tubes are used mainly to detect weak signals, their utility is greatly affected by their noise. This is true, for example, for the 20-inch MCP photomultiplier tubes used in high-energy physics research. We have built an MCP luminescence test system by coincidence testing method, and have analyzed the sources of such MCP luminescence by contrast test. We find that this MCP luminescence is due to electron multiplication in the photomultiplier tube. In order to analyze the proportion of MCP luminescence noise in an MCP photomultiplier tube, a noise model of the tube is established, including various sources of noise such as thermal electron emission from photocathode, MCP luminescence, MCP noise electron, glass luminescence, and ion feedback. Then we set up a test and evaluation system of MCP luminescence, measuring count-rate variations of 20-inch MCP photomultiplier tubes under incident light with different numbers of photoelectrons per pulse and different pulse rates. Through a series of calculations, the ratio of the noise from the MCP luminescence to the total noise of the 20-inch MCP photomultiplier tubes was determined. The results show that the luminescence noise of the MCP accounts for about 7 to 22% of the noise of the whole tube. Our analytic method can be extended to analyze the main noise sources of other MCP-type photomultiplier tubes, a direction worth pursuing to reduce noise and further improve the overall performance of MCP photomultiplier tubes.