Erbium doping

Fig. 15. Erbium-doped fiber amplifier where x represents spHces and WDM is a wavelength division multiplexer combining the signal and pump...

In the past few years, erbium doped materials gained much attention in the field of optical communications, since the Er ion shows a broad optical emission at 1540 nm [111], within the main wavelengths window in the telecommunication technology. For this reason Er can be suitable as an active element for the generation and amplification of light in optical devices [112,113], also if limitations for the realization of an efficient planar amplifier are related to the small cross section for Er excitation (typically 10 -10 cm according to the matrix). In order to enhance Er ion pumping efficiency, a possible... 

Desurvire, E. Erbium-doped Amplifiers. Principles and Applications, Wiley New York, 1994 pp 1-770 (see particularly Chapter 4). 

An optical microcavity produced by the latter process has been applied to tune the emission from erbium-doped PS [Zh6], Erbium compounds like Er203 are known to exhibit a narrow emission band at 1.54 pm, which is useful for optical telecommunications. Several methods have been used to incorporate erbium in PS. A simple and economical way is cathodic electrochemical doping. External quantum efficiencies of up to 0.01% have been shown from erbium-doped PS films under electrical excitation [Lo2]. The emission band, however, is much broader than observed for Er203. This drawback can be circumvented by the use of an optical cavity formed by PS multilayers. In this case the band is narrowed and the intensity is increased because emission is only allowed into optical cavity modes [Lo3]. 

Pollack also observes that the transition probabilities in his erbium-doped crystal change with concentration. He ascribes the decrease in emission intensity of certain transitions to reductions in radiative-transition... 

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. 

Researchers (AT T Bell Laboratories) have demonstrated that erbium-doped devices (Fig. 12) can boost signals traveling at any bit rate, transmission networks can be upgraded by simply changing the transmitters (and receivers). Virtually any video data or voice signal can be dumpled like marbles into one end of the transparent light pipes and roll out intact at the other end/ ... 

Rg. 12. Erbium-doped light amplifier. Light from a diode laser pump excites erbium ioas in segment of an optical fiber. These ions then emit light and thus boost a passing optical signal. (After AT T Bell Laboratories)... 

Nielsen, T.N., et al. 3 28 Tb/s 82 x 40 Gh/s) Transmission Over 3 < 300 km of Nonzero-dispersion Fiber Using Dual C- and L-band Hybrid Raman/Erbium-doped Inline Amplifiers, Optical Fiber Communication Conference, post-deadline paper 29, March 2000. 

For the continuous-wave semiconductor (AlGaAs) distributed feed back lasers (DFB) used in telecommunication technology today a nonlinear refractive index n2=S cm2/GW would be necessary for all-optical switching, which is presumably impossible to reach. Including an Erbium doped fiber amplifier (EDFA) the needed nonlinearity drops only by a factor of ten. 

Interest in the development of metal-organic precursors for the lanthanide elements is due to the many important apphcations of lanthanide-containing materials. These include erbium-doped semiconductors for use as optical fiber communications, lanthanide-doped GaN for fiiU color displays, high-temperature superconductors, and lanthanide-doped ferroelectric see Ferroelectricity) phases. Despite the importance of these materials, lanthanide film growth precursors... 

As was earlier reported, flexible properties of sol-gel technology may be used for modification of PLE spectra of the incorporated lanthanides. In particular, appearance of the strong band at PLE spectrum at 360 nm for the emission wavelength 1.54 pm was observed for the erbium-doped monolith xerogel silica-titania or titania/opal structure [3,4], However, in ftie case of excitation terbium in composite YAG/titania xerogel/opal the obtained PLE... 

Particularly high spontaneous emission enhancements can be attained with emitters that have very narrow emission lines. Atomic transitions, e. g. in rare-earth elements have such narrow emission lines. For this reason, rare-earth doped cavities are a prime example of the emission enhancement provided by resonant cavities. The emission spectrum of an erbium-doped Si/Si02 resonant cav-... 

Among particularly useful laser transitions of Er3+ are 53/2 113/2 at 0.85 ym and 113- 115/2 at 1-6 The latter wavelength is absorbed by the ocular media of the eye. thereby offering protection for the retina. Erbium-doped glass lasers were developed extensively for possible eye-safe applications (27). The spectroscopic properties and relaxation of Er T in a ErCl3-(AlCl3)x vapor complex have been studied (81 ) with potential application for stimulated emission. 

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