The authors achieved 11%–14% slope efficiency of solar-pumped laser by Cr-codoped Nd:yttrium aluminum garnet ceramic and Fresnel lens focusing from natural sunlight. The laser output of 24.4W was achieved with 1.3m2 Fresnel lens. The maximum output for unit area of sunlight was 18.7W∕m2, which is 2.8 times larger than previous results with mirror collector. The utilization of Cr3+ ion enabled efficient absorption and energy transfer to Nd3+ ion of solar spectrum. The fluorescence yield at 1064nm for various pumping wavelengths was measured both for Crcodoped and nondoped laser media, and 1.8 times enhancement of laser output from sunlight is predicted.

We propose a simple and efficient pumping approach for a high-power solar-pumped laser by using a liquid light-guide lens (LLGL) and a hybrid pumping cavity. A 2×2 m Fresnel lens is used as a primary concentrator to collect natural sunlight; 120 W cw laser power and a 4.3% total slope efficiency are achieved with a 6-mm diameter Nd:YAG rod within a 14-mm diameter LLGL. The corresponded collection efficiency is 30.0 W/m(2), which is 1.5 times larger than the previous record. This result is unexpectedly better than that of Cr:Nd:YAG ceramics. It is because the scattering coefficient of Cr:Nd:YAG ceramics is 0.004cm(1), which is 2 times larger than that of the Nd:YAG crystal, although both have similar saturation gains.

The authors propose an energy cycle based on a renewable fuel. Magnesium is chosen as an energy carrier and is combusted with water to retrieve energy using many power devices. MgO, the combustion residue, is reduced back to Mg by laser radiation generated from solar and other renewable energy sources. They have achieved an energy recovery efficiency of 42.5% for converting MgO to magnesium, using a laser. Combined with a demonstrated 38% efficiency for converting an artificial sunlight source (metal halide lamp) into laser output energy indicates that the proposed energy cycle is already in a feasible range for practical use.

We use a one-shot measurement technique to study effects of laser prepulses on the electron laser wakefield acceleration driven by relativistically intense laser pulses (lambda=790 nm, 11 TW, 37 fs) in dense helium gas jets. A quasimonoenergetic electron bunch with an energy peak approximately 11.5 MeV[DeltaE/E approximately 10% (FWHM)] and with a narrow-cone angle (0.04pi mm mrad) of ejection is detected at a plasma density of 8 x 10(19) cm(-3). A strong correlation between the generation of monoenergetic electrons and optical guiding of the pulse in a thin channel produced by picosecond laser prepulses is observed. This generation mechanism is well corroborated by two-dimensional particle-in-cell simulations.

A simple, compact, and efficient diode-side-pumped linear intracavity frequency doubled Nd:YAG rod laser with 50 ns pulse width and 124 W green output power Rev. Sci. Instrum. 81, 073104 (2010); 10.1063/1.3457000High-efficiency and economical solar-energy-pumped laser with Fresnel lens and chromium codoped laser medium Appl. Phys. Lett. 90, 261120 (2007); 10.1063/1.2753119Self-mode locking in a diode-pumped self-Q -switched green laser A solar pumped laser system with 7%-9% slope efficiencies has been developed. A Fresnel lens ͑2 ϫ 2 m, f = 2000 mm͒ is mounted on a two-axis sun tracker platform and focuses solar radiation toward laser cavity, which embraces Cr:Nd:yttrium aluminum garnet ceramic rod. The maximum emitted laser power is 80 W corresponding to maximum total area performance of 20 W / m 2 for the Fresnel lens area. This solar laser system would be used as a section of power plant in a magnesium energy cycle as a cost-efficient solar energy converter. Using direct solar radiation into laser, 4.3% net conversion efficiency has been achieved.