Two concave reflection mirrors (with 1000 mm curvature radius and 50 mm diameter) were used in our experiment, both mirrors with a hole near the edge and were positioned to form co-center cavity, therefore the laser could repeatedly pass and refocus in the Raman cell to achieve a high SRS conversion efficiency and reduce SRS threshold for pump laser. In this paper we reported the H 2 SRS in multiple-pass cell pumped by the fundamental frequency output of a Q-switched Nd: YAG laser.

Hydrogen is an excellent Raman medium for its high stimulated Raman gain coefficient and good flowability which can rapidly dissipate the heat generated by SRS process. Stimulated Raman Scattering (SRS) is an effective means of laser wavelength conversion. Finally the possibility of two-photon style DPALs (diode pumped alkali laser) are discussed, such alkali lasers can give output wavelengths in the shorter end of visual spectroscopy (400-460 nm) and are expected to get application in underwater communication and material laser processing. Different pumping paths are tried and by the recorded spectra, transition routes of cesium are deducted and concluded. Two photons of near infrared region are used to excite alkali atoms to n 2 D 5/2, n 2 D 3/2 or higher energy levels, then the blue fluorescence of (n+1) 2 P 3/2,(n+1) 2 P 1/2→n 2 S 1/2 are observed. Here we carried out research on two-photon excitation alkali fluorescence. But for alkali atoms such as cesium, relatively large absorption cross sections of several low, cascading energy levels enable them properties such as up conversion. This is a successful try to extend the spectral range of a laser to the shorter wavelength by SRS, and this design may play an important role in the fulfillment of high power red lasers.Īchieving population inversion through multi-photon cascade pumping is almost always difficult, and most laser medium work under 1-photon excitation mechanism. With the smaller magnification M, the threshold could further decrease, and the conversion efficiency could be improved further. The threshold is measured to be 0.62 MW, and at the pump energy of 16.1 mJ, the conversion efficiency is 34%. We found this design is especially efficient to reduce the threshold of SRS, and increase conversion efficiency. The consequent 532nm light is confined in intra- cavity SRS with travelling wave resonator, and the focal of one mirror of cavity is overlap with the center of the other mirror of the cavity. A negative branch confocal resonator with M= 1.25 is used for the frequency-doubling of Nd: YAG laser. In this paper, An Q-switched intra-cavity Nd: YAG/CH 4 frequency-doubled Raman lasers is reported. Intra-cavity SRS has the advantages of high intra-cavity laser intensity, low-SRS threshold, and high Raman conversion efficiency. Among these configurations, the intra-cavity type is particularly attractive. To obtain efficient Raman conversion in SRS, many researchers have studied different types of Raman laser configurations. Stimulated Raman scattering (SRS) is a powerful tool for the extension of the spectral range of lasers. Using these emissions, continuous-tunable mid-infrared laser with metastable Xe can be promisingly produced. It indicates that the 6p 0 atoms strongly tend to decay through the emissions between the excimer states. Under some circumstance, the ratio of the 6p 1 to 6p 0 atoms reaches about 80%. Then these excimers dissociate to produce substantial 6p 1 atoms. The mid-infrared ASEs lead to excimers correlating to the 6s’ 1 enormously generated. Therefore, it must be yielded by the superposition of Xe 2* excimer transitions.

It indicates that there should exist the relationship between these two phenomena. The thresholds of ASE peak 1 and the generation of 6p 1 atoms are both about 1.5 mJ. Simultaneously, substantial 6p 1 atoms are populated.

In this work, new phenomena, intensive mid-infrared amplified spontaneous emissions (ASEs), are found after two-photon excitation of Xe from the ground state to the 6p 0 state. However, there are sparse studies based on Xe. Rare gas laser systems with Ne (2p 53p), Ar (3p 54p), and Kr (4p 55p) atoms have been investigated. Recently, the optically pumped rare gas lasers have been attracted extensive attention.

Jingwei wan