Transient grating spectroscopy on:
[Wikipedia]
[Google]
[Amazon]
where Λ is the distance between the interference stripes, λ, the wavelength of the pump pulse, and θ, the angle between the two incident overlapping beams.Hoffman, F., Short, M., Dennett, C. ''Transient grating spectroscopy: An ultrarapid, nondestructive materials evaluation technique''. Materials Research Society, vol 44, 2019 The regions of the sample in the constructive interference fringes become thermally/vibrationally excited, and in combination with the unexcited fringes, creates a standing wave of wavelength Λ, also known as a
Overview
Transient grating spectroscopy is anoptical
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
technique used to measure quasiparticle
In condensed matter physics, a quasiparticle is a concept used to describe a collective behavior of a group of particles that can be treated as if they were a single particle. Formally, quasiparticles and collective excitations are closely relate ...
propagation. It can track changes in metallic materials as they are irradiated
Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and p ...
.
It is a pump-probe method in which short-lived standing waves are generated upon a sample surface. This is performed by combining two simultaneous pump laser beams with an angle (theta) between them, which creates an interference pattern on the sample, similar to the interference pattern generated by the well-known double slit experiment
In modern physics, the double-slit experiment demonstrates that light and matter can exhibit behavior of both classical Particle, particles and classical Wave, waves. This type of experiment was first performed by Thomas Young (scientist), Thom ...
. The space between the regions of constructive interference is given by the following equation:
where Λ is the distance between the interference stripes, λ, the wavelength of the pump pulse, and θ, the angle between the two incident overlapping beams.Hoffman, F., Short, M., Dennett, C. ''Transient grating spectroscopy: An ultrarapid, nondestructive materials evaluation technique''. Materials Research Society, vol 44, 2019 The regions of the sample in the constructive interference fringes become thermally/vibrationally excited, and in combination with the unexcited fringes, creates a standing wave of wavelength Λ, also known as a surface acoustic wave
A surface acoustic wave (SAW) is an acoustic wave traveling along the surface of a material exhibiting elastic (solid mechanics), elasticity, with an amplitude that typically decays exponentially with depth into the material, such that they are c ...
. The surface acoustic waves act as transient absorption or reflection gratings that can be probed with a continuous laser that is pulsed immediately after the pump beams. The probe beam is either diffracted through or reflected from the surface, depending on the nature of the sample, toward a detector. The surface acoustic wave fluctuations modulate the diffraction or reflection of the probe beam at the surface of the sample. Its intensity gets monitored by the detector as a function of time. The intensity of the diffracted or reflected probe beam will converge at a baseline level, where no surface acoustic wave is interfering with the diffraction or reflection of the probe.
References
Time-resolved spectroscopy {{spectroscopy-stub