Harmonic Generation of Microwave Phonons

📖 The Scoop

The ability to produce coherent phonons of microwave frequency provides a much needed means of investigating fundamental phenomena in solid state physics at frequencies never before attained. It is shown for the first time that second and third harmonics of the fundamental acoustic wave are also generated. The fact that the secondharmonic acoustic power was observed to be proportional to the square of the fundamental and the third-harmonic acoustic power proportional to the cube of the fundamental establishes the nonlinearity of the generation mechanism. Second-harmonic generation of longitudinal phonons in nonpiezoelectric Z-cut quartz was observed. The generation mechanism is common to all dielectric media. This demonstrates that coherent phonon generation is not restricted to relatively rare piezoelectric materials. The highest frequency at which microwave phonons can be generated is limited to 80 Gcps by present-day highpower microwave sources. The successful generation of harmonics of microwave phonons enhances the possibility of extending the present limit well into the millimeter range. Fundamental research of this type can lead to such practical control devices as microwave delay lines since the acoustic delay time of one centimeter of quartz is the same as that of 500 meters of waveguide. (Author).

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