Pulsed multielement semiconductor laser with an unstable resonator

Abstract

It is shown that the interaction of helicity-1 waves of gravity and matter in a thin slab configuration produces new types of instabilities. Indeed, a spin-2 helicity-1 mode interacts strongly with the shear motion of matter. This mode is unstable above a critical wavelength, λ c = πc 2 /2Gρ. This should be compared with Jeans wavelength, λ J = πc 2 s /Gρ, where c s is the sound speed. The two instabilities are of course different. For the case analysed, a plane parallel configuration, Jeans instability appears through a density wave perturbation, the material collapsing into a set of plane-parallel slabs. On the other hand, the helicity-1 wave instability induces a transverse motion in the fluid that tends to shear in the material along the node of the perturbation.PACS numbers: 0430, 0430N Acoustic waves are affected by gravitational forces. One of the consequences is Jeans instability [1] (see also e.g. [2, 3]) produced above a certain critical wavelength. There is an electromagnetic counterpart in plasma density waves. In the limit of large wavelengths their frequency square tends to a finite positive value, and the plasma acquires the plasma frequency, whereas in the Jeans case the frequency square turns negative. This is noted by Weinberg [4] but he does not go further. Plasma density waves can be seen as longitudinal electromagnetic waves which are not possible in a vacuum but are present in media with the plasma frequency having the role of a photon mass. By the same token acoustic waves can be identified with longitudinal waves of the gravity field but now, instead, they possess an imaginary mass. Transverse electromagnetic waves, in addition to longitudinal waves, are also modified in a plasma and acquire a mass equal to the plasma frequency. The questions posed in this paper concern waves of the gravity field, or wave metric perturbations, propagating in matter. More specifically, we are interested in the following question: are there waves which get a finite real mass or do they get an imaginary mass leading to instabilities other than Jeans?Waves of the gravity field can be classified according to their spin and helicity. Here we are interested in spin 2 waves which can have helicities 2, 1 and 0. Helicity-2 waves represent radiative gravitational waves and are simply called gravitational waves. Helicity-1 waves, as well as helicity-0, do not exist in a vacuum but can propagate in matter. The propagation of waves of the gravity field through matter has been studied in two main contexts,

Comparative studies of fission fragment and electron beam driven solid-state lasers and reactor-laser system modeling

“…The total power output of the lasers can vary widely. Fractions [48,52], tens [49,53], hundreds [51,[54][55][56][57], thousands [50,[57][58][59][60], and millions [61,62] of Watts have been reported, however short beam pulses (on the order of ~1 ns) put total energy outputs to less than 1 J. CW lasers are difficult to construct due to the power limitations of most electron gun devices operating in steady state conditions. Typical optical power output is on the order of 1 mW [52,63].…”