Temporal Carrier Research Articles

Reference-beam system for measuring relative small-surface local irregularities of a reflective object

We present an optical technique for measuring irregularities on a small local surface ( approximately lambda/100). This new technique uses a narrow laser beam as a local probe. The probe beam interferes with a reference beam. We use a 90 degrees phase delay on the reference beam to increase the sensitivity. We show that if the test surface vibrates laterally, the collected power of the interferogram encodes as amplitude modulations, on a sinusoidal temporal carrier, the local surface irregularities.

Behavior of Si Photoelectrodes under High Level Injection Conditions. 3. Transient and Steady-State Measurements of the Quasi-Fermi Levels at Si/CH3OH Contacts

Real-time measurements of the photovoltage rise and decay at the back of lightly doped, thin, long lifetime Si photoelectrodes were recorded subsequent to a variety of spatial and temporal carrier generation impulses. The functional form of the rising portion of the photovoltage signal is sensitive to charge transport processes, and this signal was used to validate experimentally the hypothesis that charge transport in these samples under high level injection is primarily driven by diffusion, as opposed to drift. The decay of the photovoltage signal back to its equilibrium value yielded information concerning the surface recombination velocity, Sf, of the various Si/CH3OH redox couple contacts. These data validated the relatively high surface quality of the Si/liquid interface in contact with a variety of redox species. Furthermore, the low surface recombination velocities are in agreement with prior theoretical and experimental estimates of interfacial charge-transfer rate constants for semiconductors in contact with nonadsorbing, outer-sphere, redox species. The front surface recombination velocity data also provided a needed boundary condition for modeling the carrier concentration dynamics and allowed quantification of the difference between the quasi-Fermi levels at the back and front surfaces of the samples at all times of experimental interest. Digital simulation and analytical modeling were performed to compute the gradients in the quasi-Fermi levels for samples operated under steady-state, open-circuit, high level injection conditions. In no case was the difference between the quasi-Fermi level value at the back of the sample and its value at the solid/liquid contact greater than 10 meV. These data, combined with those described in parts 1 and 2, comprise a relatively complete picture of the transport and recombination processes that occur at these types of semiconductor/liquid contacts.

Spatiotemporal frequency multiplex heterodyne interferometry

To have the advantages of both spatial and temporal heterodyne techniques and to make efficient use of the limited spatiotemporal frequency bandwidth of image detection systems, we propose a technique of spatiotemporal heterodyne interferometry using both spatial and temporal carrier frequencies. By means of spatiotemporal frequency multiplexing, the technique permits the simultaneous recording of multiple-phase objects on a single space–time interferogram.

The cortex as interferometer: The transmission of amplitude, frequency and phase in cortical structures

Concerning the perceptual phenomenon of object constancy: an object may be represented exhaustively in all its transformations only by introducing phase operators (as well as amplitude). The transmission of phase and a metric capable of handling phase in the central nervous system is thus requisite. Interferometry meets these requirements. The occurence of interferometry in the cortex is shown to be feasible. The cortex, it is suggested, codes frequency spatially and in the time domain. This permits phase, also, to be represented by latency changes in the time of arival of patterning upon the cortex. Latency changes are effected by delay methods and may be considered as a kind of temporal modulation of frequencies. For interferometry to work a carrier and a metric must be provided by the brain. The temporal carrier for cortical information can be constituted of indegenous cortical rhythms synchronized by a thalamic trigger. Great flexibility of measuring power is needed in order to account for the generation of information by the brain. The dipole can be shown to provide the metric capable of just such power.