| Summary: | 碩士 === 國立虎尾科技大學 === 光電與材料科技研究所 === 99 === Even though the field of EM wave amplification for microwaves has been rather mature and enjoying many available technologies, amplifying a lightwave already left the laser resonant cavity can be a tough problem with very little choice. Long before erbium-doped optic fiber amplifier (EDFA) has become a reality and mass produced, other lightwave amplification schemes have been considered, even realized, and tested. Among them, the most noticed are the Stimulated Raman Scattering (SRS) and the Stimulated Brillouin Scattering (SBS). Comparing with the EDFA, a major difference in them both is that in their lightwave amplification mechanisms, no atomic (molecular) energy levels are involved, and only pure plasma physics processes are relevant. However, up to this day, it has been concluded that both the SBS and SRS amplification effects are so much weaker than the gain that stimulated emission provides in a doped-fiber amplifier that Raman and Brillouin amplifiers tend to involve very long distances and very high pump powers.
On the other hand, since the EDFA amplification approach is entirely limited by quantum transition physics among energy levels, even though it may at best provide 980 nm and 1490 nm spectrum intervals for communication purposes, overall, it fails to give a real wide-band, flat-top working spectrum. Furthermore, apparently EDFA can only amplify lightwaves guided by optic fibers, not those flying in the open space and of arbitrary wavelengths and amplitudes.
Nevertheless, mankind in fact has been longing for a lightwave-enhancing technology that is essentially unrestricted by available atomic energy levels, and at the same time can be applied on lights propagating in free space or within optic fibers. In man-made plasma sources, and in fusion experimental machines (such as the Tokamak), we often witness the working of a plasma instability called Weibel EM instability. However, in these cases, Weibel instability is an undesirable path for system energy loss. In natural environments, Weibel instability also plays a major role in causing gamma ray bursts observed by satellites. Here, we intend to direct the application of Weibel instability to a new direction, viz., amplifying essentially lightwaves of arbitrary wavelengths and amplitudes in either open or fiber-confined space, in a fashion more like the aforementioned SRS and SBS. The approach adopted is using controlled “plasma”, in the form of vertically (with respect to the incident light) oscillating electrons, to trigger the Weibel instability to further cause exponential growth of the incident lightwave amplitude.
This current research mainly aims to test the feasibility of such lightwave Weibel amplification theory as a preliminary step toward the ultimate goal of air-borne lightwave amplification.
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