Ultrafast laser-scanning time-stretch imaging at visible wavelengths.

Optical time-stretch imaging enables the continuous capture of non-repetitive events in real time at a line-scan rate of tens of MHz-a distinct advantage for the ultrafast dynamics monitoring and high-throughput screening that are widely needed in biological microscopy. However, its potential is limited by the technical challenge of achieving significant pulse stretching (that is, high temporal dispersion) and low optical loss, which are the critical factors influencing imaging quality, in the visible spectrum demanded in many of these applications. We present a new pulse-stretching technique, termed free-space angular-chirp-enhanced delay (FACED), with three distinguishing features absent in the prevailing dispersive-fiber-based implementations: (1) it generates substantial, reconfigurable temporal dispersion in free space (>1 ns nm) with low intrinsic loss (<6 dB) at visible wavelengths; (2) its wavelength-invariant pulse-stretching operation introduces a new paradigm in time-stretch imaging, which can now be implemented both with and without spectral encoding; and (3) pulse stretching in FACED inherently provides an ultrafast all-optical laser-beam scanning mechanism at a line-scan rate of tens of MHz.

[Effects of laser wavelength on detection of metal elements in water solution by laser induced breakdown spectroscopy].

In the present paper, aiming at the problem of laser induced breakdown spectroscopy (LIBS) applyication in ocean detection, the effects of laser wavelength on the detection of Ca in water solution were investigated. The evolvement characteriza tion of electron density was studied by analyzing the time resolved spectra of the plasma. The experimental results show that the lifetime of plasma is about 1 200 and 600 ns respectively induced by 1 064 and 532 nm laser.

[Experimental investigation of Pb in soil slurries by laser induced breakdown spectroscopy].

Laser induced breakdown spectroscopy (LIBS) has been shown to be a promising technique for element analysis with many advantages including on-line, real time, standing off and multi-element detection capability. In the present paper, the LIBS experiments for Pb in slurry samples were carried out with the motivation of developing an in-situ sensor for monitoring heavy metal. A Q-switched Nd : YAG laser operating at 532 nm with repetition frequency of 10 Hz was utilized to generate plasma on the prepared slurry samples, which were doped with same weight manganese as reference and varied concentration of lead.