There is a great desire to extend ultrasonic techniques to the imaging and characterization of nanoobjects. This can be achieved by picosecond ultrasonics, where by using ultrafast lasers it is possible to generate and detect acoustic waves with frequencies up to terahertz and wavelengths down to nanometers. In our work we present a picosecond ultrasonics setup based on miniaturized mode-locked semiconductor lasers, whose performance allows us to obtain the necessary power, pulse duration and repetition rate. Using such a laser, we measure the ultrasonic echo signal with picosecond resolution in a 112 nm thick Al film deposited on a semiconductor substrate. We show that the obtained signal is as good as the signal obtained with a standard bulky mode-locked Ti-Sa laser. The experiments pave the way for designing integrated portable picosecond ultrasonic setups on the basis of miniaturized semiconductor lasers.

中文翻译：

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使用微型半导体激光器的皮秒超声波

人们非常希望将超声波技术扩展到纳米物体的成像和表征。这可以通过皮秒超声波来实现，其中通过使用超快激光器，可以产生和检测频率高达太赫兹、波长低至纳米的声波。在我们的工作中，我们提出了一种基于微型锁模半导体激光器的皮秒超声波装置，其性能使我们能够获得必要的功率、脉冲持续时间和重复率。使用这种激光器，我们以皮秒分辨率测量沉积在半导体基板上的 112 nm 厚铝膜中的超声回波信号。我们表明获得的信号与使用标准大块锁模 Ti-Sa 激光器获得的信号一样好。