Air-backed optoacoustic transmitter for high amplitude quasi-monopolar wave

Unipolar acoustic wave is advantageous for high resolution imaging and detection due to its high frequency characteristic. However it is difficult to achieve the unipolar waveform using with traditional piezoelectric transducers. Here, we demonstrate unipolar acoustic wave form using an optoacoustic approach by directly exposing the absorbing layers of photoacoustic transmitters to air (i.e., an air-backed optoacoustic transmitter), which simultaneously increases signal amplitudes by employing an acoustic matching layer on the air-side.