Ultrasound amplification by stimulated emission of radiation

A group of researchers in the United States designed an electromechanical system consisting of ultrasonic oscillators that emit both spontaneously and by stimulated emission like atoms in an optical laser. The group anticipated that ultrasonic analogues (uasers) will allow experiments not possible with optical lasers. Hence, they used acoustical resonators of various sizes and shapes. The group detected a shift of the uasing frequency in response to a drop of water 10 ⁵ times smaller than the mass of cavity. Their estimates show that perhaps the actual accuracy could reach as much as 10 ⁸.