A Method of Measuring the Parameters of the Response Speed of Photodetectors
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A METHOD OF MEASURING THE PARAMETERS OF THE RESPONSE SPEED OF PHOTODETECTORS S. B. Bychkov,1 I. V. Volkov,1 A. I. Glazov,1 I. S. Korolev,1 K. B. Savkin,1 and N. P. Khatyrev2
UDC 535.249.2
Problems arising in the measurement of the parameters of the response speed of current broadband photodetectors by the method based on measurement results of the rise time of transitional characteristics. A method is proposed for quantitative estimate of response speed, using the results of the determination of impulse response of a photodetector being examined. A pulsed fiber optic laser operating in a condition of self-synchronization of modes, and providing the generation of ultrashort (approximately 3 ps) optical pulses, serves as the source of measurement signals. A measurement installation that makes it possible to implement the proposed method of measurement is provided. Certain results of experimental testing of the method are given. Keywords: photodiode, photodetector, response speed of a photodetector, impulse response, amplitude-frequency characteristic, picosecond pulsed laser.
Introduction. High-speed photodetectors (optoelectronic converters) are widely disseminated in fiber-optic communication systems, systems of laser distance measurement and location, satellite laser range-finding sensors, and radio photon systems. It is very important for design engineers and producers of these devices to have knowledge of the dynamic characteristics of photodetectors. Photodetectors are here and thereafter understood to be systems to the optical input of which is supplied an optical signal (including modulated), where the signal of electrical output is proportional to the power of an input optical signal. P /n photodiodes and avalanche semiconducting photodiodes, as well as some vacuum and pyroelectric receivers can be used as the converter of optical power to electrical signal in such systems The rise time and fall time of the output signal for an input “stepped” optical pulse corresponds to the parameters for response speed (response characteristics of photodetectors) in accordance with the operative GOST 17772-88 (ST SEV 3789-82), “Semiconductor radiation detectors. Photoelectric and photodetector instruments. Methods of measuring photoelectric parameters and determining their characteristics.” In addition, the frequency characteristics or normalized values of the nonuniformity of the amplitude-frequency characteristics (AFC) are often shown for the bandpass range and the width of the bandwidths in the technical documentation. The most widespread criterion for the response speed of photodetectors is the rise time of the transitional characteristics of a photodetector over the range 0.1–0.9 of the established value. For this purpose, the input of a photodetector is fed an optical square pulse, the duration of which exceeds by a large factor the expected rise time of the output signal of a photodetector. The rise time of the leading edge of this test pulse must be at least no more than 30% of the expected rise time of the tr
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