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An economical and stable single-shot pulse picker design without dispersion, nonlinear effect, and limitation on wavelength is proposed. This design is composed of a periodic pulse blocker (PPB), a control unit, and a mechanical shutter. It has successfully been applied to the commercial high-fluence femtosecond laser with 11-mm beam diameter, 2-mJ pulse energy, and 1-kHz repetition rate. Significantly, by incorporating commercial optical choppers equipped with custom-designed chopper blades in the PPB, this design can accommodate lasers with fluences reaching 610 mJ/cm2 and the standard 1 kHz repetition rate typical of high-fluence lasers. Furthermore, the proposed design provides a cost-effective substitute compared to using electro-optic modulators or acousto-optic modulators. [ABSTRACT FROM AUTHOR]

We report ultra-broadband ultrasonic spectroscopy with an impedance-matched piezoelectric nanolayer, which enables optical generation and detection of a 730-fs acoustic pulse (the width of ten lattice constants). The bandwidth improvement facilitates THz laser ultrasonics to bridge the spectral gap between inelastic light and x-ray scatterings (0.1-1 THz) in the studies of lattice dynamics. As a demonstration, this method is applied to measure sound attenuation α in a vitreous SiO2 thin film. Our results extend the existing low-frequency data obtained by ultrasonic-based and light scattering methods and also show a α∝ f2 behavior for frequencies f up to 650 GHz. [ABSTRACT FROM AUTHOR]

By using femtosecond laser-ultrasonic, we demonstrate an approach to study the surface plasmon field optically excited in the interface between metal and a semiconductor thin film. By femtosecond impulsive excitation on gallium-nitride (GaN), different optical probe signals were observed when the impulse-excited nanoacoustic pulse propagated through the metal film and metal nanoslits. By analyzing the shape and temporal response of thus induced acousto-optical signals, our femtosecond laser-ultrasonic study not only reveals the plasmonic field distribution optically excited in the metal/substrate interface but also confirms that the penetration depth of surface plasmon field into the substrate agrees well with a simulation result. [ABSTRACT FROM AUTHOR]