Abstract
We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1–12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies.
Highlights
In typical solid materials, sub-terahertz (THz) coherent acoustic waves have wavelengths in the nanometre range
A bias-T was inserted in the intermediate frequency (IF) lead so that a direct current (DC) bias could be applied to the diode if required
Due to the limited bandwidth of the microwave amplifier modules and oscilloscope, it is impossible to resolve the acoustic component at 50 GHz
Summary
Sub-terahertz (THz) coherent acoustic waves have wavelengths in the nanometre range. A strong international research effort is currently aimed at using nanoacoustic waves to probe, and even to alter dynamically, the physical properties of nanostructured materials and devices Such nanoacoustic waves can, for example, be used for the ultrafast modulation of the electronic states in semiconductor nanodevices, which allows control over their optical[4,5] and electrical transport[6,7,8,9] properties. For example, be used for the ultrafast modulation of the electronic states in semiconductor nanodevices, which allows control over their optical[4,5] and electrical transport[6,7,8,9] properties Despite their successes, the laser-based nanoacoustics techniques suffer from a serious drawback, which has limited their wider use across scientific disciplines and in industry. Unlike the optical-based detection methods, most of these devices detect the signal by www.nature.com/scientificreports/
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