Detection of powerful terahertz pulses with use of termoacoustic probe

Abstract

Summary form only given. Results of measurements of electromagnetic pulses with 3 to 10 mcs duration at frequencies 0.55-0.87 THz by the thermoacoustic detector are presented. Operation of the detector is based on effect of acoustic signal generation when electromagnetic pulses are absorbed in the layered structure: radiotransparent substrate-absorber-immersion liquid. Thin metallic film of nanometer thickness sputtered onto the quartz substrate is used as an absorber. The transformation of electromagnetic radiation into acoustic pulse is performed in the film and in the liquid contacting with the film. Acoustic pulse is detected by the broadband acoustic transducer and registered with a digital oscilloscope. It is shown that for the pulse of microsecond duration the signal waveform detected by the thermoacoustic detector is completely matched to the derivative of a profile of terahertz pulse. When water and ethanol are used as immersion liquids the presence of additional film absorber is not compulsory because these liquids absorb effectively the electromagnetic radiation in frequency range 0.5-1 THz.