Detection of photoinduced electronic, thermal, and acoustic dynamics of gold film using a transient reflecting grating method under three types of surface plasmon resonance conditions

Abstract

Mechanisms of unusual signal enhancement observed for transient reflecting grating ͑TRG͒ experiments are investigated under three types of surface plasmon resonance ͑SPR͒ conditions, where two pump beams only, a probe beam only, or two pump beams and a probe beam, excite surface plasmon. A gold thin film deposited on a glass prism is measured in the Kretschmann configuration with a temporal resolution of tens of picoseconds. The signal under each SPR condition exhibits different characteristic features in signal intensity and transient behavior unlike the usual non-SPR TRG experiments. Under SPR with pump beams, high conversion efficiency from light to heat allows detection of a TRG signal 11 times larger in magnitude and much lower in background level than under a non-SPR with them. Under SPR with the probe beam, diffraction caused by heat-induced spatial modulation as described by complex reflection Fresnel coefficients is theoretically proved to enhance the TRG signal and to change transient behavior, which provides a way to get selective observation of heat diffusion near the surface. When both pump and probe beams excite surface plasmons, an additional signal is observed, almost at the same time as the optical pulse, having 100 times larger intensity than the other signals, which is due to electrons excited at the gold surface.

PHOTOTHERMAL APPLICATIONS OF LASERS: Study of Fast and Ultrafast Photothermal Phenomena at Metal-Liquid Interfaces

“…In recent works by Katayama et al (84,85), the opposite findings were reported under surface plasmon resonance (SPR) conditions, which can provide a method to observe responses of the electronic grating, temperature grating, and acoustic grating separately. A surface plasmon (SP) is a kind of surface-localized plasma wave propagating parallel to a metal-dielectric interface, which can be optically excited in an attenuated total-reflection configuration.…”

“…Heterodyne detection combined with diffraction optics improves sensitivity significantly (80,82). Use of plasmon resonance makes it possible to separately detect electronic, thermal, and acoustic contributions at the same time that signal enhancement is achieved (84,85). These techniques are just beginning to be applied, but they should be major tools for femtosecond-TG experiments, material evaluations, and interface studies.…”

“…The experiment apparatuses for TG and TRG measurements used by a number of groups (80)(81)(82)(83)(84)(85) are making it possible to perform the measurements in more sophisticated ways. Use of diffraction optics provides a simple way to get pumppulse overlaps (80), and it is especially effective for femtosecond-pulse overlaps ?…”

An impulsive stimulated scattering study of surface acoustic waves under high pressure

“…Rapid thermal expansion launches a standing SAW with a well-defined wavelength and propagation direction determined by the spacing and orientation of the grating, respectively [31,2]. A displacement of less than a nanometer gives a strong diffraction signal on the order of 10 À4 of the incident probe intensity [3].…”

Femtosecond Transient Reflecting Grating Methods and Analysis of the Ultrafast Carrier Dynamics on Si(111) Surfaces

“…As a photothermal method, we have developed a transient reflecting grating (TRG) method with a time resolution of 80 ps, and have applied it to semiconductor surfaces. 8,9 The TRG method has many advantages, such as surface selectivity, high sensitivity, background-free detection, and providing directional information. We can expect to observe carrier thermalization and carrier transport dynamics by raising the time resolution to the femtosecond time region of the TRG method.…”