Transverse stimulated Raman scattering (TSRS) is strongly generated in the third-harmonic-generation crystal potassium dihydrogen phosphate (KDP) and can even damage the KDP crystal in inertial confinement fusion drivers. In this work, a method to suppress TSRS is proposed in which the polarization control plate (PCP) is moved to a new position in the existing optical path. The proposed method can suppress TSRS significantly and doubles the laser threshold intensity in KDP crystal when the order of the PCP is 16. This result is attributed to the reduction of the gain length for the Stokes radiation. The proposed method may also be used to suppress other nonlinear effects, including transverse stimulated Brillouin scattering in large-aperture optical components.

Effective suppression of transverse stimulated Raman scattering (TSRS) in a large-aperture potassium dihydrogen phosphate (KDP) crystal is an important scientific and technical problem in high-intensity laser research and applications. In this work, a method to suppress TSRS using pulse stacking is proposed. The method suppresses TSRS significantly, with greater numbers of subpulses producing more obvious suppression effects, and the threshold intensity growth rate of the 3ω laser in the KDP crystal reaches up to about 1.9 when the stacked pulse contains four subpulses. This suppression effect is attributed to the fact that the polarization directions of adjacent subpulses are perpendicular to each other. The method can be used to suppress other nonlinear effects, including transverse stimulated Brillouin scattering in large-aperture optical devices and stimulated rotational Raman scattering in long air paths.

A new tapered semiconductor laser with an integrated multimode interference coupler is presented in this paper. The seed source of the new laser is a multimode interference coupler semiconductor laser, which overcomes the limitations imposed by the relationship between single mode output and gain medium volume in the ridged waveguide region. The simulation results show that the multi-mode interference coupler can effectively provide a spatial single-mode seed light source for the tapered output waveguide, and the tapered output waveguide of the tapered semiconductor laser can also effectively reduce the optical power density of the output laser, which verifies the feasibility of the design scheme and provides a new idea for the design of high beam quality and high power tapered semiconductor laser.

With the rapid decline of conventional crude oil’s production and transportation, heavy crude oil, heavy oil, oil sands, oil shale and other unconventional oil have gradually become the main body of the marine oil spills. The used oil spill fingerprinting methods mainly for conventional oil are facing new challenges. According to the time-resolved fluorescence spectroscopy, concentration value is introduced as a new data dimension to the fluorescence spectra and the concentration-resolved-fluorescence spectroscopy (CRFS) is developed to express more PAHs information. Laboratory simulation experiments of weathering and distillation were carried out and the results demonstrate this method has strong anti-weathering and anti-interference ability. Oil source classification of close-related heavy crude oil samples under light weathering and seawater weathering lasting 120 d are studied. 96% of the correct rate for the closely related oil source samples is achieved by combining Gabor wavelet with supported vector machine (SVM). The obtained results suggest that the newly-developed method may become specifically applicable in spilled oils identification and also can be applied to other multi-fluorophoric systems such as in petroleum exploration, dissolved organic matter in environment monitoring and petroleum exploration.

Antimonide semiconductor laser is a new type of laser with unique advantages in the 2 μm band. However, employing FP cavities causes multiple transverse modes to degrade beam quality despite achieving higher power output. In this paper, an antimonide semiconductor laser operating in 2 μm band is realized by utilizing fiber coupling and combining. Fiber combining results in higher output power, while the uniform patterns in both near-field and far-field are obtained, and the beam quality is improved. The experimental results illustrate that the output power reaches 1.2 W after 7-channel beam combination, and the near-field distribution is approximately Gaussian, while the far-field distribution is a flat-top.