Optical amplification

Shyh Wang, Principles and Characteristics of Integratable Active and Passive Optical Devices Shlomo Margalit and Amnon Yariv, Integrated Electronic and Photonic Devices Takaaki Mukai, Yoshihisa Yamamoto, and Tatsuya Kimura, Optical Amplification by Semiconductor Lasers... 

Liu B, Bazan GC (2006) Optimization of the molecular orbital energies of conjugated polymers for optical amplification of fluorescent sensors. J Am Chem Soc 128 1188-1196... 

Pu KY, Pan SYH, Liu B (2008) Optimization of interactions between a cationic conjugated polymer and chromophore-labeled DNA for optical amplification of fluorescent sensors. J Phys Chem B 112 9295-9300... 

The key prerequisite for optical amplification via stimulated emission is that the emitted photons propagate through the gain medium long enough to initiate further stimulated transitions. This condition can be expressed as... 

T. Mukai, Y. Yamamoto, and T. Kimura, Optical Amplification by Semiconductor... 

Various types of optical fibers are used for specific applications. For example, multimode fibers are used primarily in enterprise systems buildings, offices, campuses. Special single-mode transmission fibers exist for submarine applications, and for metropolitan and long-haul terrestrial applications. And in addition to these transmission fibers, there are various specialty fibers for performing dispersion compensation (dispersion compensating fiber), optical amplification (erbium-doped fiber), and other special functions. 

Khlebtsov B, Zharov V, Melnikov A, Tuchin V, Khlebtsov N. Optical amplification of photothermal therapy with gold nanoparticles and nanoclusters. Nanotechnology 2006 17 5167-79. 

With an emission at 1.3 /tm, Nd3+ is a potential candidate for optical amplification in the second telecommunication window. However, optical gain remains limited because of amplified spontaneous emission at 1.05 fim and also because of strong ESA at 1.3 /on. This ESA process, which takes place from 4F3/2 to (4G7/2, 2K13/2) and to 4G9/2 as shown in Fig. 5, is so probable that no gain is achieved around 1.3 /tm in silica fibers. In ZBLAN fluoride fibers, gain is achieved at 1.34... 

The 4Ii3/2 - 4Iis/2 infrared emission band of Er3+ ions in fluorozirconate glass is displayed in Fig. 11. The band maximum is located at 1.53 /an and the width at half-maximum is as broad as 60 nm, which favors the use of this transition for optical amplification in the third telecommunication window. In bulk geometry, 1.6 jtm CW-laser action is reported for a Cr, Yb, Er-codoped fluoroaluminate glass slab pumped by a krypton laser [114],... 

The 800 nm transition from 3H4 to 3H6 has been extensively studied because of its suitability for optical amplification in the first telecommunication window. With a branching ratio of 90%, this transition is not perturbed by amplified spontaneous emission of competing transitions. The 1.47 jum emission from 3H4 to 3F4 is also of special interest for optical amplification between the second and third telecommunication window. Both transitions arise from the 3H4 level, which can be excited directly at 800 nm with a laser diode. This level can also be pumped by 2-step up-conversion, either from a mini-YAG Nd at 1.06 m or from a laser diode at 975 nm, in (Yb, Tm) codoped glasses. Details on these applications are given in Sec. 8.5.2. 

Optical amplifiers are essential components for the development of high capacity telecommunication networks. Silica fibers are characterized by a low-loss optical window that ranges from 1.2 to 1.7qm, as shown in Figure 4. That window is divided into the ultrashort (XS), short (S), conventional (C) and long (L) bands. The first two bands are centered at 1.3 and 1.47 qm, while the C- and L-bands are equal to 1530-1565 run and 1565-1625 nm, respectively. Amplification in the C- and L-bands is commonly achieved with Er +-doped silica fibers. On the other hand, amplification at 1.47 qm and 1.3 qm with Tm + and Pr + ions requires the use of materials with lower phonon energy than silica. High gain optical amplification was demonstrated in the XS, S, and C, telecommunication windows with rare earth-doped... 

Chemical lasers are pumped by reactive processes, whereas in photodissociation lasers the selective excitation of certain states and the population inversion are directly related to the decomposition of an electronically excited molecule. Photolysis has been the only source of energy input employed in dissociation lasers, although it appears quite feasible to use other energy sources, e.g. electrons, to generate excited states. Table 4 lists the chemical systems where photolysis produces laser action. It is appropriate to begin the discussion of Table 4 with the alkali-metal lasers since Schawlow and Townes in 1958 35> chose the 5 f> 3 d transitions of potassium for a first numerical illustration of the feasibility of optical amplification. These historical predictions were confirmed in 1971 by the experimental demonstration of laser action in atomic potassium, rubidium and cesium (Fig. 14). 

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