In frequency domain laser ultrasonics, the pulsed laser source used for ultrasound excitation in conventional laser ultrasonics is replaced by a low power, amplitude modulated laser source. The acoustic signals are detected using an interferometer or contact transducer, coupled to a RF lock-in amplifier or vector network analyzer. The detection bandwidth reduction afforded by this technique all...

Two-photon excitation provides efficient optical sectioning in three-dimensional fluorescence microscopy, independently of a confocal detection. In two-photon laser-scanning microscopy, the image resolution is governed by the volume of the excitation light spot, which is obtained by focusing the incident laser beam through the objective lens of the microscope. The light spot being strongly elon...

Abstract We calibrate the distorted wave Born approximation (DWBA) for electron impact excitation processes empirically. Differential cross sections (DCSs) for the excitation of the 2p53s, 2p53p, 2p54s and 2p54p configurations of Ne and the 3p54s and 3p54p configurations of Ar by electron impact are calculated using DWBA for incident energies between 20 and 100 eV. The calculated results are co...

SERS labels are a new class of nanotags for optical detection based on Raman scattering. Central advantages include their spectral multiplexing capacity due to the small line width of vibrational Raman bands, quantification based on spectral intensities, high photostability, minimization of autofluorescence from biological specimens via red to near-infrared (NIR) excitation, and the need for on...

We studied the phenomenon of photothermal bleaching - a gradual reduction of contrast agent particles during repeated scans in photoacoustic microscopy. The dependence of the photothermal bleaching rate on the excitation pulse energy, pulse duration, and the absorber's size was determined while the laser focal diameter was held constant. Our results showed that, the dependence of the phototherm...

Laser experiments with optically excited frozen gases entail the excitation of polarization waves. In a continuum approximation the waves are dispersionless, but their frequency depends on the direction of the propagation vector. An outline is given of the theory of transient phenomena that involve the excitation of these waves by a resonant dipole-dipole transfer process.

We describe a state-of-the-art tunable ultraviolet (UV) Raman spectrometer for the 193-270 nm spectral region. This instrument allows for steady-state and transient UV Raman measurements. We utilize a 5 kHz Ti-sapphire continuously tunable laser (approximately 20 ns pulse width) between 193 nm and 240 nm for steady-state measurements. For transient Raman measurements we utilize one Coherent Inf...

575 news & views the tunnel current while slowly varying the time delay between pump and probe. As with many experiments using near-field probes, the key to success lies in suppressing spurious effects while boosting the desired signal above the noise floor. Shigekawa and colleagues demonstrate a clever lock-in detection scheme akin to heterodyne detection in a radio receiver to boost their sen...

Abstract Effect of laser wavelength on the carrier-phonon dynamics and damage threshold silicon is studied numerically. Laser excitation in using Three-Temperature Model (3TM). We consider evolution electron, hole, lattice temperatures separately including band-gap re-normalization effect optical properties silicon. Finite Difference Time Domain method used to model field. Damage calculated 3TM...

We have developed a multimodal multiphoton laser-scanning microscope for cell imaging featuring simultaneous acquisition of differential Coherent Antistokes Raman Scattering (D-CARS), two-photon fluorescence (TPF) and second harmonic generation (SHG) using a single 5 fs Ti:Sa broadband (660-970 nm) laser. The spectral and temporal pulse requirements of these modalities were optimized independen...