Theoretical studies of solar-pumped lasers

The power output of a black body solar-pumped laser as a function of time (computer graphic solutions) and under steady state conditions (analytic conditions); computer analyses of polymerization using lasers; and metallic sodium as a laser medium were studied

Theoretcial studies of solar-pumped lasers

A method of pumping a COhZ laser by a hot cavity was demonstrated. The cavity, heated by solar radiation, should increase the efficiency of solar pumped lasers used for energy conversion. Kinetic modeling is used to examine the behavior of such a COhZ laser. The kinetic equations are solved numerically vs. time and, in addition, steady state solutions are obtained analytically. The effect of gas heating filling the lower laser level is included. The output power and laser efficiency are obtained as functions of black body temperature and gas ratios (COhZ-He-Ar) and pressures. The values are compared with experimental results

Theoretical studies of solar-pumped lasers

In any lasing medium the emission wavelength should be chosen where there is little self absorption. As emission and absorption spectra for metallic vapors did not seem available, therefore, estimates were made of these cross sections for sodium vapor as functions of wavelength. Although absolute values were not obtained, information on where the emission wavelength should occur became evident. The method of obtaining quantities proportional to the cross sections versus wavelength is outlined. A further comparison based on alternative expressions for the absorption and emission cross sections over a limited wavelength range is made

Quantum phase transition induced by Dzyaloshinskii-Moriya in the kagome antiferromagnet

We argue that the S=1/2 kagome antiferromagnet undergoes a quantum phase transition when the Dzyaloshinskii-Moriya coupling is increased. For $D<D_c$ the system is in a moment-free phase and for $D>D_c$ the system develops antiferromagnetic long-range order. The quantum critical point is found to be $D_c \simeq 0.1J$ using exact diagonalizations and finite-size scaling. This suggests that the kagome compound ZnCu$_3(OH)$_6$Cl$_3$ may be in a quantum critical region controlled by this fixed point.Comment: 5 pages, 4 figures; v2: add. data included, show that D=0.1J is at a quantum critical poin