Реферат_англ (Автокорреляционный метод приема ультракоротких импульсов)

SYNOPSIS

Master’s thesis « Autocorrelation method of reception of ultrashort pulses» consists of 82 pages, 35 images, 4 tables, 31 references and 4 appendix.

Keywords: autocorrelation method, autocorrelator, ultrashort pulses, a Michelson interferometer.

To obtain the full characteristics of ultrashort pulses it is necessary to measure not only its spectrum and energy, but also the time profile. The technique for measuring the spectrum and energy is well known. The measurement of the time profile of ultrashort pulses is a complex problem solely because of the small pulse duration.
Traditional methods of temporal measurements provide a temporal resolution that is orders of magnitude inferior to the duration of ultrashort pulses of modern lasers. In connection with this, only optical methods based on correlation methods are used to measure the characteristics of ultrashort pulses.

Information on the time characteristics of ultrashort pulses can be obtained by measuring the autocorrelation function of the intensity. The autocorrelation function is the dependence of the visibility of the interference fringes on the output of the interferometer on the path difference or the time delay between the interfering beams.

The autocorrelation function is obtained by linear addition of the original pulse with its copy shifted in time. In the case when the main function is strictly periodic, the graph of the autocorrelation function will also have a strictly periodic function. From this graph it is possible to judge the periodicity of the main function and consequently its frequency characteristics. Interferometers of various constructions are often used as the instruments for measuring the autocorrelation function.

In developing the experimental facility it was decided to use an autocorrelation receiver of optical ultrashort pulses based on the Michelson interferometer. The system consists of a semitransparent mirror of great thickness separating a beam of light, and two deaf mirrors. A most important element in the operation of an autocorrelation receiver is a system that ensures the displacement of a moving mirror relative to a semitransparent mirror to change the path difference between the reference and information pulses. When the difference in the stroke between these pulses changes, their interference occurs and leads to a change in the readings of the photodetector. Interference occurs when the difference in the stroke between these pulses changes, and this leads to a change in the signal of the photodetector. In this installation the movable mirror is located on the speaker membrane. When voltage is applied to the speaker the diaphragm moves with the mirror to a level corresponding to the applied voltage. As a result of the motion of the dynamics the difference in the arms changes and an interference pattern arises that is fixed by the photodetector module.

This experimental facility will allow carrying out various experiments connected with the investigation of the characteristics of optical ultrashort pulses, such as duration and energy spectrum.