Optic-acoustic effect

This aspect is not included here, but is related to optical flow diagnostics. It is based again on the principle of the optical Doppler effect. Multifunctional equipment is available for noncontact measurements of flow-induced vibration on surfaces of structural elements, for acoustic measurements, and for calibration of accelerometers and vibration transducers. 

The microwave acoustic effect may be defined as the auditory perception of microwave radiation which is a form of electromagnetic energy which occupies the part of spectrum between ordinary radio waves and infrared and optical waves. This definition may... 

Figure 2.15. Spectra of the damping y(u>) and of the absorption c"(w) (with arbitrary absorption units) derived from our model (2.127)—(2.130), at temperatures ranging between 3 and 70 K. At low temperatures we may distinguish in the spectrum pure acoustical effects below the threshold, and combined effects (acoustical + optical) above the threshold. At high temperatures, both branches contribute to yield the broad and asymmetrical lineshape. The energy origin has been chosen at the unperturbed exciton band botton. So the absorption spectra show a red shift even at low temperatures, which should be considered when comparing the model with the experimental spectra of Figs. 2.12-13.

Another model-free method for active damage detection is based on directional transducers. For passive sensing. Section 16.9 has already discussed the use of directional strain rosettes (both piezo and optical) to effectively detect an acoustic source without the need for a structural model. For active sensing, directional transmission as well as reception of guided wave can be achieved with phased-array transducers. 

Betts, G.E., Ray, K.G., and Johnson, L.M. 1990. Suppression of acoustic effects in litliium niobate integrated-optical modulators. In Technical Digest on Integrated Photonics Research, Vol. 5, pp. 37-38. Optical Society of America, Washington, DC. 

The converse piezoelectric effect, when electric field induces mechanical deformation, has special importance because of its influence on the electro-optical responses they are mainly imwanted since they result in misalignment, but with clever design can be used to re-heal alignment. It is interesting to note that in the audio frequency ranges, the vibrations result in audible acoustic effects, implying their possible use in electromechanical transducers. ... 

As I look back at this experience, it was an awesome adventure to be alone, during and for an interval of time after this discovery, with the apparatus showing one new effect after another, when there was no one in the Illinois Physics Department experienced in NMR with whom I could talk. Little did the early NMR resonance community realize that the analogue of spin echo hidden memory contained in excited phases of all kinds of states of matter, including plasmas, would be obtained in the future by use of optical laser, electric, and acoustic pulses as well. And now today the use of spin echoes is a standard procedure for magnetic resonance imaging of the human body for medical diagnosis. 

The temperature tuning coefficient of Te02 is 0.025 nm/°C, so it is clear that in order to combat the effects of thermal heating of the crystal due to incident optical and acoustic power, as well as environmental considerations, a good level of thermal control is needed. This can be in the form of a TE-cooled enclosure. This will deal to a certain extent with the need to achieve analyser wavelength repeatability. However, it does not address the issue of wavelength reproducibility between AOTF modules, which impacts the transportability of calibrations and datasets between analysers. 

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