We demonstrated laser diode pumped quasi-continuous-wave random laser in Nd3+ doped YAG nanopower with a one-mirror structure. Beside usual phenomena associated with laser, like threshold behavior and substantially narrowing of emission spectra, chaotic pulsing behavior was observed above a certain pumping level, which is explained as disturbed relaxation oscillation in random cavities. Possible relation between random lasing in such one-mirror structure and coherent backscattering effect, which is also referred as weak localization, is discussed with much interest.
At the recent years a technology of ceramic laser media on the base of crystals with a cubic symmetry has been developed. The perspective of the usage of ceramic materials in many different applications including high-power short pulse lasers stimulates the work on the systematic study of the properties of these new laser media. In this report a nonlinear refractive index, n2, was studied for several garnet and sesquioxide laser ceramics using Z-scan method. This technique with a “top-hat” probe beam intensity distribution was used. Nonlinear indices in the range of (2-6)x10-13 were measured for YAG, Y2O3, Lu2O3, and Sc2O3 ceramic samples.
These data together with the laser and spectroscopic parameters of several Nd3+ and Yb3+ doped crystals of a cubic symmetry were used to estimate in the complex the properties of laser ceramics for the application in high-power pulsed-repetitive laser-drivers for inertial confinement fusion (ICF) program. A high heat conductivity of ceramic materials is a profitable characteristic for this application as compared to glasses which are used now for experiments in ICF at single shots regime. Compared to single crystals, ceramic elements provide laser designers with a variety of new design options for the projects of laser-drivers. The usage of ceramic active elements with low and increased n2 values in the channels of a powerful laser facility is discussed.
In this report, polycrystalline Yb:Y 2O3 ceramic laser has been demonstrated for the first time. With a pump power of 11 W at 937 nm, 0.75 W cw laser output at 1078 nm was obtained. The laser had a threshold of 4.7 W and a slope efficiency of 12.6% when an output coupler of R = 98% was used.
A non-fusional fiber coupler is demonstrated for the high power double clad fiber lasers with optical adhesive technique. The fiber coupler is constructed by polishing a non-doped single-clad fiber at a bevel angle and then adhere to the doped double-clad fiber with an optical adhesive. The pump light is launched through the single-clad fiber to the doped double-clad fiber. The polished angle for the optimal coupling depends on the fiber numerical aperture and coupling efficiency of 90 percent can be achieved. The bend effects on the coupling efficiency is investigated and find that the degrade of coupling efficiency is very sensitive to distance between the bend to the coupling point. Finally, laser radiation is demonstrate with a Nd-doped double clad fiber in low pump regime.
Using Raman fiber laser (RFL), 350 m singlemode fiber and 50% feedback fiber Bragg grating (FBG) at 1484 nm, we obtain a high-efficiency ultra-broadband (1434 - 1527 nm) CW Supercontinuum (SC) centered at 1484 nm with an average output power of 2.08 W and nonlinear conversion efficiency of 94%. Spectral density of 22.3 mW/nm is obtained. The output of the SC for different fiber lengths in the Raman and the singlemode are reported.
We demonstrate a novel ring cavity for diode-pumped double-clad Tm-doped ber laser, which is constructed by placing the 45o angle-polished output end before the input end and the pump and laser power can re-launched into the ber. This design can reduce the reabsorption by using short length of bers without loss of pump efficiency. Furthermore, by adjusting the distance between the ber end and the objective lens, uni-directional output can be obtained. With a 80 cm long ber, 2.7 W single-mode continuous-wave output is generated for 11.5 W launched pump power.
Highly efficient Nd:YAG ceramic laser at 1064 nm was demonstrated. Using 1 W LD end-pumping scheme, with 883 mW pumping, 499 mW 1064 nm CW laser output has been obtained corresponding to an optical to optical efficiency of 56.5%. High power CW Nd :YAG ceramic rod laser was also demonstrated. The maximum output power of 62.5 W with was obtained at 1064 nm. The optical to optical conversion efficiency is 21.6%.
A high-power Raman fiber laser (RFL) with maximum output power of 4.11 W/1239 nm and 2.24 W/1484 nm is obtained using a continuous wave (CW) 8.4 W/1064 nm Yb-doped double-clad fiber laser (DCFL) as a pump, phosphorous-doped fiber (PDF) and cascaded cavities made with fiber Bragg Gratings (FBG). RFL performance for the 300, 700 and 1150 m PDF lengths and output mirror reflectance was experimentally investigated by observing maximum output power, slope efficiency, threshold power, and full-width at half maximum at both the first and second Stokes wavelength.
Highly efficient Nd:YAG ceramic laser at 1064 nm was demonstrated. Using 1 W LD end-pumping scheme, with 883 mW pumping, 499 mW 1064 nm CW laser output has been obtained corresponding to an optical to optical efficiency of 56.5%. High power CW Nd:YAG ceramic rod laser was also demonstrated for the first time. The maximum output power of 3 1 W with 1 8.8% slope efficiency was obtained at 1064 nm. The potential of Nd:YAG ceramic laser was also discussed.
The mutual effects of stimulated Raman scattering and four- wave mixing (FWM) in phosphosilicate fibers is studied experimentally and theoretically. It is found that the output spectra depend on the launched condition strongly. When only one mode is excited in the fiber, the output spectrum is determined by the competition of stimulated Raman scattering between the SiO2 and P2O5. The SiO2 Raman line is dominative with lower pump power or using of short length fiber. While the pump power is increased or the long fiber is used, the P2O5 Raman line increased and the SiO2 Raman line is suppressed. When two modes are excited in the fiber, the effects of four-wave mixing is dominative and the spectrum only consist of lines of FMW-assisted Raman scattering of SiO2.
The characteristics of a LD-pumped Nd:YVO4 laser operating at 1340-nm are reported. The maximum output power of 157mW with a slope efficiency of 3 1 .5% has been realized at the incident pump power of 515mW. With a KTP crystal for intracavity-frequency-doubling , 3.6 mW red laser at 670-n.m is obtained. Keywords: LD-pumped, Nd:YVO4, intracavity-frequency-doubling
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