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Frequency Domain Techniques for Analyzing Picosecond Optical Pulses

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Final rept. 10 May 1988-1 Oct 1989

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Using the techniques of Fourier analysis, any periodic time domain function will have a unique frequency domain transform. It is therefore possible to use frequency domain measurements to understand a time domain signal. Fourier analysis implies that picosecond laser pulses would have frequency components which range into the microwave bands. The technique of picosecond demodulation is one way of generating microwaves from laser pulses. Picosecond demodulation uses laser pulses to generate electron bunches at a photocathode. The electron bunches are then accelerated and radiate electromagnetic waves. Based on this technique it is possible to measure the microwave spectrum of a picosecond optical pulse training. This report develops the theory of picosecond demodulation and shows that the frequency spectrum generated is related to the Fidrier transform of the time domain envelope of the laser pulse train. Based on the theoretical development, a prototype device, called a picosecond demodulator, has been built. Using this device, several experiments are reported which a verify the theory of picosecond demodulation and b demonstrate that frequency domain techniques can be used to characterize picosecond pulses. These results indicate that frequency domain techniques are easy and inexpensive to implement and provide an accurate supplement to time domain measurements using auto-correlators or streak cameras. Keywords Optical detectors Laser pulses Theses.

Subject Categories:

  • Lasers and Masers
  • Optical Detection and Detectors

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