Beating = optical mixing

The capillary wave frequency is detected by an optical heterodyne technique. The laser beam, quasi-elastically scattered by the capillary wave at the liquid-liquid interface, is accompanied by a Doppler shift. The scattered beam is optically mixed with the diffracted beam from the diffraction grating to generate an optical beat in the mixed light. The beat frequency obtained here is the same as the Doppler shift, i.e., the capillary wave frequency. By selecting the order of the mixed diffracted beam, we can change the wavelength of the observed capillary wave according to Eq. (11). 

Hoffmelster series = lyotropic series holes (in semiconductors) 3.171 homodlsperse colloids 1.1.14. 1.1.28,1.7.53 homod me beating see optical mixing homointeraction 1.4.72... 

Optical mixing techniques are the optical analogs of the beating techniques developed in radio-frequency spectroscopy (Forrester, 1961). They have made possible the application of light scattering to the study of the dynamics of relatively slow processes such as macromolecular diffusion, the dynamics of fluctuations in the critical region/and the motility of microorganisms. 

Cummins, H. Z. and Pike, E. R. (eds.), Photon Correlation and Light Beating Spectroscopy, Plenum, New York (1974). This book contains lecture notes on various aspects of optical mixing techniques, including discussions of precision, noise, the relative merits of digital and analog techniques, and the design of autocorrelators. 

The sample in a DLS experiment is well-dispersed in a saspending medium. In a typical DLS experiment, the sample is illuminated by a single-wavelength laser beam. To measure the Doppler widths, the DLS instrument uses optical mixing or light-beating techniques to translate the optical ftequencies (—6 x 10 Hz with the 488-nm line of an Ar laser) to frequencies near 0 Hz (dc) that can be easily measured. In most DLS instruments, a photomultiplier tube (PMT) is used as a nonlinear mixer because its output is proportional to the square of the electric field falling on its photosensitive surface. 

We will close this section on the experimental work with a brief review of two types of experimental techniques - the light beating or optical mixing technique using a spectrum analyzer and the autocorrelation counting technique. For a deeper and more detailed discussion the reader is referred to reviews by Cummins (54) and Benedek (55). The approach we give is similar to the description given by Chu (/4). 

On the other hand, what we can measure is the time correlation of intensity fluctuations defined by eqn [8], For the self-beating of the electric field in the optical mixing method, we have the Siegert relation for Gaussian statistics systems, providing the important relationship between andg ... 

Beat noise Electrical noise generated at a receiver due to the mixing of optical signal power and optical ASE noise power at the detector. 

---