A new photonic approach of microwave waveform generator based on time-domain synthesis is proposed and experimentally demonstrated, in which two single-drive Mach-Zehnder modulators biased at quadrature point are severed as optical pulse carvers and various microwave waveforms can be generated by carving and overlapping optical field envelopes. The theoretical analysis and simulation are developed. In experiment, a square waveform with 50% duty cycle, triangular waveform with full duty cycle, and sawtooth (or reversed-sawtooth) waveform with 50% duty cycle are generated. Furthermore, a frequency doubling sawtooth (or reversed-sawtooth) waveform with full duty cycle is also obtained.
Abstruct-In this paper, we investigate temperature dependence of breakdown voltage Ii,? from -40 to 110°C in separate absorption, grading, charge, and multiplication (SAGCM) InPnnGaAs avalanche photodiodes (APD's) with a range of device parameters. The experimental data shows that I/br is approximately a linear function of temperature, with a temperature coefficient qeXp between 0.13 and 0.16 V/"C. A physical model is developed and it demonstrates that I;,. indeed varies linearly with temperature with a temperature coefficient V t h e about 0.155 V P C . It also explains successfully the small variation of qeYp among the APD's. Good agreement between the physical model predictions and experimental data of published InP-based APD's is also obtained. This good agreement demonstrates that the proposed physical model is appropriate to model the temperature dependent characteristics in any InP-based APD's.
A 3-mm-gapped GaAs photoconductive semiconductor switch is triggered by a 1.6 μJ laser diode. Effects of the rectangular spot's layout and the triggering position on the electric field threshold of nonlinear mode are investigated. As the illuminated position moves from the cathode to the anode, the effective illumination optical energy varies. In that case, when the rectangular spot is perpendicular to two electrodes the electric field threshold increases linearly. And when the rectangular spot is parallel to the electrodes, the electric field threshold exhibits an asymmetric parabola-like curve.
The photonic energy of terahertz wave is in the same order of magnitude as the rotational and vibrational energy levels of organic and biological macromolecules, so it has unique advantages in detecting cells and biological macromolecules. However, in the life environment, the dynamic time scale of cell-environment interaction and structural conformation change of biological macromolecules are within picosecond to millisecond, and water has strong absorption to terahertz wave, which has become the bottleneck problem for the detection of cells and biological macromolecules by terahertz technology. In this article, we developed a set of terahertz single measurement system based on the tilt wave front of grating pulse technique. The system was employed for the terahertz detection of trace living cervical cancer cells. We achieved transient detection of the terahertz pulse time-domain waveform of the living HeLa cells. The characteristic absorption peaks were identified by Lambert-Beer law, respectively, at 0.49, 0.71, 1.04, 1.07, 1.26 and 1.37 THz. The absorbance is proportional to the cell concentration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.