A compact, asymmetric probe, planar transient grating spectroscopy system

Transient grating spectroscopy (TGS) is a rapid and non-destructive technique for measuring thermal, acoustic, and elastic properties of solid materials with a multitude of uses across many areas of materials research. Current TGS systems require optics tables and cumbersome amounts of space for an entire setup, restricting TGS to being a lab-based method. This paper presents a new design for TGS systems that rotates the probe laser beams around the axis of the pump beam, allowing for an asymmetric probe, planar, optically 2D setup. This, in turn, allows the setup to be significantly simplified, which enables the setup presented in this paper to be roughly nine times smaller in volume than contemporary setups while being much easier to build, align, and operate. Part of the size reduction was enabled by a mono-homodyne system and the removal of the chopper. This system was benchmarked against an existing TGS system using a single-crystal tungsten sample. This showed that it can produce the same surface acoustic wave frequency data as the existing system. This design enables TGS to be more widely adopted for use in more varied and compact environments because of its smaller size and simplicity.