Coherent acoustic phonons in nanomechanical systems: an ASOPS-microscopy investigation

O. RISTOW; M. HETTICH; A. BRUCHHAUSEN; S. BÄCHLE; J. GREBING; A. ERBE; E. SCHEER; T. DEKORSY

Söllehaus

Workshop; Workshop Nanomechanics of the Collaborative Research Center Konstanz (SFB767); 2010

Collaborative Research Center SFB767 (DPG-Germany)

In this work we present an investigation of the dynamics of single Si3N4-based nanostructures probed by the high-speed ASOPS pump-probe method. This method based on two asynchronous linked femtosecond unidirectional ring lasers of ~1 GHz repetition rate, one providing the pump pulse, the other providing the probe pulse. Thetime delay between both pulses is realized by introducing a fixed, actively stabilized frequency offset of 5 kHz in the repetition rates of the two lasers. The absence of mechanical moving parts allows for very fast scanning rates and an unprecedented signal-to-noise ratio. [1,2]We have coupled this set-up to a microscope, achieving a focal spot size of approximately 1.3 mm. Furthermore, using a CCD camera and a motorized scanning stage, we are able to resolve and address single nanostructures as well as to scan over larger sample areas with high spatial resolution. We demonstrate the potential of our system to investigate nanostructures, e.g. nanomechanical systems. In particular, we show results of pump-probe experiments analyzing the dynamics of nanomechanical resonators based on Si3N4. Such a typical nanostructure is shown in Fig.1. Thanks to the high spatial resolution of our system, we are able to accurately address these cantilevers and study their time-resolved vibrational properties.