The Research On Acousto-Optic Interaction Technique In Solid

Acousto-optic technique deals with the physical effects caused by the interaction oflight and sound. Acousto-optic technique has been used to all kinds of domains,especially perform computationally intensive signal processing. When the laser onlyacting on the solid surface, acousto-optic technique has been used to nondestructivetesting field early, and when the sound waves and light waves spread into solid medium,the interaction of light and sound will occur. As a cross technology, acousto-optictechnique involves a wider range of knowledge. On the base of our acousto-opticsystem laboratory, the dissertation is focused on three aspects key technology ofacousto-optic technique, such as the laser scanning ultrasonic nondestructive testing,acousto-optic correlator and one dimensional ultrasound photonic crystal. The mainworks are as follows:(1) Surface acousto-optic interaction in an opaque solid, owing to ultrasonicwavelength as small size, ultrasonic wave has been used to detecting internal defects ofall kinds of material, while laser has been used to fast imaging for sound wavesmicrovibration of material surface. According to those pictures, we can judge internaldefects of material, and CT tomographic imaging technology being further introduced,material internal defects image of three dimension graphics have been more clearlypresented.Therefore through a certain times of projecting, the effective reconstructiondata has been obtained, while combining corresponding tomography algorithms and thecorrection algorithms, clear three dimensional picture of the sample has also beenachieved.(2) Interior acousto-optic interaction in a transparent solid, based on sound and lightinteraction being occurred in certain incidence angle (especially the Bragg angle)simultaneity in solid internal, acousto-optic correlator research has been wide applied totypical time integrating acousto-optic correlator. In the article, trough compensation forthe nonlinear effect of crystal Bragg, correlation signals has been extracted, finally along time domain signal processing system has been designed. (3) Interior acousto-optic interaction in a transparent solid, the ultrasonic photoniccrystals will be formed when sound and light being in same incidence angle. In thearticle, the transmission properties of phononic crystals in one dimensional piezoelectricFibonacci quasi-periodical superlattices are studied using the transfer matrix method.The transmission coefficients in piezoelectric Fibonacci quasi-periodical superlatticesare compared with those of the phononic crystals with periodical structure and withnon-piezoelectric Fibonacci quasi-periodical structure. The results show that the bandgap can also be found in the phononic crystals with both piezoelectric andnon-piezoelectric Fibonacci quasi-periodical superlattices, and the frequency range ofthe gap in piezoelectric Fibonacci quasi-periodical superlattices is larger than that ofboth periodical structure and non-piezoelectric Fibonacci quasi-periodical structure. Thepiezoelectric property of quasi-periodic sequences has been firstly introduced to theband structure of phononic crystals at home and abroad.(4) Acoustic wave incident angle of the one-dimensional piezoelectric sequencehas a great influence on transfer characteristic.The results show that sequence phononcrystal transmission depends on the incidence angle selection in one dimensionalquasi-periodic piezoelectric, phonon transmission has been related with incidence angle.The suitable angle can be designed to a stable filtering device.(5)Through similarity of phononic and photonic crystals,it has been discovered thatphononic crystal superlattice has present a phenomenon of the energy band fold samedas photonic crystal and semiconductor superlattice, so that stronger similarity can beoccured in the three kinds of superlattices, the mature method in semiconductor andphotonic crystal superlattice can be used to study the phononic crystal superlattices.(6) Interior acousto-optic interaction in a transparent solid,1-D ultrasonic photoniccrystal has been investigated in this article. It is new field that the acousto-opticinteraction has been introduced into1-D ultrasonic photonic crystal. Through theanalysis of acoustic wave propagation in solid medium,1-D ultrasonic photonic crystalcan be modulated by the sound waves. While the calculation for dispersion relation ofultrasonic photonic crystal band gap structure and transmittance, it has been foundthat1-D ultrasonic photonic crystal of a sinusoidal refractive index distribution haswider or narrower band gap than traditional photonic crystals. The band gap of1-Dultrasonic photonic crystal has also studied to relation with the dielectric layer refractive index, the incident angle and the thickness of the dielectric layer using transfer matrixtheory, some important results have been achieved.