Effect of CC Coherent Vibration on Relative Raman Scattering Cross Sections of All-trans β-Carotene

We have determined the Raman scattering cross sections（RSCSs） of fl-carotene for C=C and C-C stretching modes, with the 1444 cm^-1 Raman band of cyclohexane as internal standard, in different solvents at low concentrations by measuring Raman intensity. The results show that RSCSs of β-carotene were 10^6-10^7 times larger than the general RSCSs, we analyzed that this enhancement was caused not only by the resonance Raman effect but also by nonlinear coherent CC vibration in aqueous β-carotene. Moreover, overtone and combinations of it were also observed and their intensities were 10%-20% of those of their fundamentals when β-carotene was dissolved in non-polar solvents, respectively.

Lasing Behavior of BMPPV:PVK Mixture in Microcavity

The surface emitting microcavity is formed by sandwiching a polymer film containing poly(para-phenylene vinylene)(BMPPV) and poly(N-vinylcarbazole)(PVK) between a DBR with a reflectivity of 99.5% and a silver film. The sample is optically pumped by a 337.1 nm line of nitrogen laser with 10 ns pulses at 20 Hz repetition rate . The lasing phenomenon is observed in BMPPV and PVK mixture microcavity. The full width at half maximum (FWHM) is 6 nm at the peak wavelength of 460 nm. The lasing threshold energy is estimated to be about 5 μJ.

Applications of Semiconductor Lasers

An overview of the applications of semiconductor lasers is presented. Diode lasers are widely used today, and the most prevalent use of the laser is probably in CD and DVD drives for computers and audio/video media sys- tems. Semiconductor lasers are also used in many other fields ranging from optical fiber communications to display, medicine and pumping sources.

Development of Fiber Lasers and Their Applications

Development of fiber lasers, especially the latest progress in high power fiber lasers, and the problems of the commercialization of high power fiber lasers, are discussed. Research on other kinds of fiber lasers, such as microstructure fiber laser, ultrashort pulse fiber lasers, Raman fiber lasers are also involved.

Application of Photonic Crystals in Semiconductor Lasers

Photonic crystals(PCs) have attracted much considerable research attention in the past two decades. They are artificially fabricated periodic dielectric structures. The periodic dielectric structures have photonic band gap(PBG) and are referred to as photonic band gap materials. This paper mainly introduces one-dimensional (1-D) and 2D PCs applied in the semiconductor lasers.

All-fiber Based Er^(3+)∶Yb^(3+) Co-doped Fiber Laser

An all-fiber based Er~ 3+ ∶Yb~ 3+ co-doped double clad fiber laser operating at 1550nm is demonstrated. By using 9m long Er~ 3+ ∶Yb~ 3+ co-doped fiber(EYDF) as the gain medium, and using a pair of fiber Bragg gratings as wavelength filters, the line-width of the output laser is as narrow as 0.2nm and the output power is more than 6mW. The fluorescent effect of the laser before its emission is also studied. And it is found that the Er~ 3+ ∶Yb~ 3+ co-doped double-clad fiber laser also exhibits a high gain for Yb~ 3+ transition near 1080nm.

High Power Fiber Bundle Array Coupled LDA Module

An optical fiber bundle array coupling module with high output power is presented in this paper. The device integrated the coupling technique of the high power laser diode array (LDA) and the micro-ball lenses fiber array. This module can efficiently couple the output laser of the LDA into 19 fibers array with micro-ball lens end-surface. The difference of the couple efficiency between the flat-end fiber and micro-ball-end fiber is discussed. The micro-ball lenses fiber array made of 19 fibers have the same fiber core diameter of 200 m, and then the end-surfaces of 19 fibers are fused to 19 micro-ball lenses. The micro-ball lenses fiber array are fixed precisely in the neighborhood on the V-grooves, and the fiber array has the same arrange period with the semiconductor laser units of LDA. This configuration of micro-ball lens fiber array can greatly reduce the divergence of the laser beam from all directions, and a very efficient laser beam homogenizer and shaper are obtained. Finally, high output power of 30.1 W of the fiber coupled LDA is achieved, and the maximal coupling efficiency is >83% with the numeral aperture (NA) of 0.16.

Red Light Vertical-Cavity Surface-Emitting Lasers

Vertical-cavity surface-emitting lasers (VCSELs) have entered into commercial market over the last few years. The paper describes the progress of visible (red) VCSELs in particular. The Basic experimental structures are reviewed, with emphasis on distributed Bragg reflectors, gain media, as well as detuning.lt also points out some technical issues that must still be resolved. Finally, the polarization of VCSELs devices is discussed.