Detection of light is one of the most fundamental physical processes playing a very important role in both nature and technology. In nature, this process underlies vision, thus providing an opportunity to perceive the world around us. Numerous photodetectors in technology allow the quantification of the detection of optical signals, expanding the spectrum of detected radiation.
The problem of detecting optical signals by optical methods themselves was first formulated apparently by Bloembergen [1]. However, this idea has not been adequately developed. In paper [2] it was shown that the signal-to-noise ratio could be improved by using nonlinear radiation detectors in which the signal transformation begins from an absorption transition. It was shown in papers [3] that photocounts appear in conventional photodetectors due to the strong Coulomb instability of a weak electron current produced in the detector by a signal being detected. This suggests that in detectors, instead of free electrons, the electrons that are bound in atoms, ions, or molecules can be used, where they are well stabilized by a strong Coulomb field of nuclei.
Below a possible scheme for detecting weak optical signals by laser means is described. At present microcavities are created which can be used in the Bloembergen scheme, providing the passage from spontaneous to stimulated effect, thereby substantially improving the scheme.
To achieve the record temporal velocities at the detection of optical signals it is necessary to understand in details the processes, taking place in photocathode and near it. In the first instance, it is necessary to study the nature of photocounts, the basic effect of photodetecting. This effect was lately studied not very well and, as we shall see, it contains some problems.
An alternative approach to the theory of photocounts is discussed. Mechanisms of sharpening of electronic distribution at the expansion of many-electron packets is investigated. Arising of such inhomogeneities initiates a disintegration of many-electron system on smeared on- electron formation. It is shown that interelectronic Coulomb interaction results in the sharpening and localization of such one-electron formations. The motion of an electronic wave packet in the uniform field in the interelectrode space of the vacuum photodetector is investigated. It is shown that the dimensions of such a packet must be of an order or more than one micron. It is shown that such localized charges can give rise to abrupt pulses of the current in the external circuit of the photodetector. The determination of parameters of such a packet by powerful laser pulse scattered is discussed. The motion of one-electron wave packet in the nonuniform field of a negative charged spherical electrode is numerically investigated. It is shown that there is the possibility to unsqueeze electron packets in the transverse direction to macroscopic size by scattering on such electrodes. An experiment of observation of such macroscopic packet on the luminophore screen is discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.