Inside every cellphone lies a tiny mechanical heart, beating several billion times a second. These micromechanical resonators play an essential role in cellphone communication. Buffeted by the cacophony of radio frequencies in the airwaves, these resonators select just the right frequencies for transmitting and receiving signals between mobile devices.
With the growing importance of these resonators, scientists need a reliable and efficient way to make sure the devices are working properly. That’s best accomplished by carefully studying the acoustic waves that the resonators generate.
Now, researchers at the National Institute of Standards and Technology (NIST) and their colleagues have developed an instrument to image these acoustic waves over a wide range of frequencies and produce “movies” of them with unprecedented detail.
Imaging Tiny Vibrations
Movies made at NIST, using an optical interferometer, capture the atomic-scale vibrations of microresonators similar to those found in cellphones.
The researchers measured acoustic vibrations as rapid as 12 gigahertz (GHz, or billions of cycles per second) and may be able to extend those measurements to 25 GHz, providing the necessary frequency coverage for 5G communications as well as for potentially powerful future applications in quantum information.
The challenge of measuring these acoustic vibrations is likely to increase as 5G networks dominate wireless communications, generating even tinier acoustic waves.
The new NIST instrument captures these waves in action by relying on a device known as an optical interferometer. The illumination source for this interferometer, ordinarily a steady beam of laser light, is in this case a laser that pulses 50 million times a second, which is significantly slower than the vibrations being measured.
The laser interferometer compares two pulses of laser light that travel along different paths. One pulse travels through a microscope that f ..
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