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Showing papers on "Erbium published in 1995"


Journal ArticleDOI
TL;DR: The analysis describes the modification of the spontaneous emission rate as a function of refractive index, and serves to determine for the first time the radiative lifetime of Er in silicate glass, a parameter of great importance for Er-doped optical gain materials in telecommunication technology.
Abstract: Spontaneous emission is interpreted as a consequence of interaction between matter and electromagnetic radiation. Previous experiments, using for instance Rydberg atoms or semiconductor structures, have demonstrated that spontaneous emission can be influenced in cavities or near mirrors [1 ‐ 7]. In this Letter we will show an extremely simple way to modify the spontaneous emission rate, merely by bringing liquid films with certain refractive index in contact with a silica glass surface which is locally doped with luminescent Er 31 ions. Erbium shows clear photoluminescence (PL) around 1.54 mm [8], an important wavelength in optical telecommunication [9]. The theoretical description of spontaneous emission is usually based on concepts from quantum electrodynamics such as vacuum fluctuations and a creation and annihilation formalism. The inclusion of a dielectric interface requires special attention [10]. In this case, the variation in the spontaneous emission rate can be accounted for by the local classical density of states (DOS), which appears in Fermi’s golden rule. In this Letter, a straightforward calculation of the local DOS is performed, given the Fresnel equations for transmission and refraction at a dielectric interface. The analysis describes our data on the modification of the spontaneous emission rate as a function of refractive index, and serves to determine for the first time the radiative lifetime of Er in silicate glass, a parameter of great importance for Er-doped optical gain materials in telecommunication technology. Two samples of bulk sodalime silicate glass (refractive index n0 › 1.5) were implanted with 500 keV Er ions. Sample A was covered with a 120 nm thick Al film as a stopping layer, and sample B was uncovered during implantation. After implantation, the Al layer was etched off, and a thermal anneal at 512 ‐ C was performed. Erbium depth profiles for both samples, as determined using 2 MeV 4 He 1 Rutherford backscattering spectrometry (RBS), are shown in Fig. 1. The open data points for sample A show a profile peaked at the glass surface, with a half-width of 70 nm. The measured profile is a convolution of the detection resolution and the actual profile which is discontinuous at the surface. The drawn line shows the deconvoluted profile, which has a surface concentration of , 0.25 at. %. The solid data points in Fig. 1 show a Gaussian profile for sample B, centered at 150 nm depth from the surface, where the Er concentration is 0.17 at. %. The full width at half maximum is 100 nm. PL spectroscopy was carried out at room temperature. The 514.5 nm line of an Ar-ion laser was used to excite the Er, and the luminescence was spectrally analyzed with a monochromator and detected with a liquid-nitrogen cooled Ge detector. PL decay measurements were performed after exciting with a 1.5 ms pulse, using a digital averaging oscilloscope. Further details on sample preparation and PL measurements can be found in Ref. [11]. Various liquids, with refractive indices ranging from 1.3 to 1.7, and thickness in the order of a mm, were brought in contact with the sample surface on the front, while the luminescence signal was collected on the back side (see inset in Fig. 2).

226 citations


Journal ArticleDOI
TL;DR: In this article, a singlemode fiber-compatible optical waveguides were fabricated by use of Na+ ↔ K+ ion exchange, and the effect of upconversion on optical gain was shown and discussed.
Abstract: Soda-lime silicate glass has been locally doped with 0.2-at. % erbium by 3.0- and 5.0-MeV ion implantation. Single-mode fiber-compatible optical waveguides were then fabricated by use of Na+ ↔ K+ ion exchange. Characteristic photoluminescence (PL) of Er3+ centered at 1.54 μm is observed on excitation at 1.48 μm. For low pump intensity the PL decay is nearly single exponential with a lifetime of 7.2 ms. At high intensity it becomes nonexponential as a result of cooperative upconversion, an interaction between excited Er ions. Self-consistent modeling of the PL intensity and decay data yields an upconversion coefficient of 3.2 ± 0.8 × 10−24 m3/s. The effect of upconversion on optical gain is shown and discussed. An extrapolation of measured optical gain shows that 1 dB/cm of net gain is possible in the present Er-implanted soda-lime glass.

141 citations


Journal ArticleDOI
TL;DR: The optical activation, excitation, and concentration limits of erbium in crystal Si are studied in this paper, where Er is trapped in the crystal at concentrations ranging from 3×1016 to 7×1019 Er/cm3, as measured by secondary ion-mass spectrometry.
Abstract: The optical activation, excitation, and concentration limits of erbium in crystal Si are studied. Preamorphized surface layers of Czochralski‐grown (Cz) Si(100), containing 1.7×1018 O/cm3, were implanted with 250 keV Er at fluences in the range 8×1011–8×1014 cm−2. After thermal solid‐phase epitaxy of the Er‐doped amorphous layers at 600 °C, Er is trapped in the crystal at concentrations ranging from 3×1016 to 7×1019 Er/cm3, as measured by secondary‐ion‐mass spectrometry. Photoluminescence spectra taken at 77 K show the characteristic Er3+ intra‐4f luminescence at 1.54 μm. Photoluminescence excitation spectroscopy shows that Er is excited through a photocarrier‐mediated process. Rapid thermal annealing at 1000 °C for 15 s increases the luminescence intensity, mainly due to an increase in minority‐carrier lifetime, which enhances the excitation efficiency. Luminescent Er forms clusters with oxygen: the maximum Er concentration that can be optically activated is determined by the O content, and is (3±1)×1017...

118 citations


Journal ArticleDOI
TL;DR: In this paper, the luminescence properties of III-V semiconductors doped with Er atoms have been investigated and compared with those of Er-doped electroluminescent devices.
Abstract: Optoelectronic materials doped with Er atoms are receiving widespread attentions due to their impact on optical communication systems operating at 1.54 μm. Optical amplifiers based on Er-doped fibers have demonstrated major improvements in link distance, data rates and reduced needs for signal regeneration. III–V semiconductors doped with Er offer the prospect of very stable, temperature-insensitive, laser diodes emitting at 1.54 μm. This paper provides a review of the luminescence characteristics of III–V semiconductors doped with Er atoms. Aspects of Er incorporation in the III–V crystal host, photoluminescence properties, and prototype electroluminescent devices are addressed. Details of some of the first observations of photoluminescence of Er atoms in III–V nitride semiconductors, in particular GaN epilayers, are discussed. The GaN epilayers were optically excited using an argon-ion laser and spectra, centered at 1.54 μm, were observed at 6, 77 and 300 K. The spectra display many of the allowed transitions typical of the Er 3+ configuration and are nearly as intense at room temperature as at 77K. This result indicates that the wide bandgap III–V semiconductors may be ideal host materials for Er-doped electroluminescent devices.

112 citations


Patent
31 Aug 1995
TL;DR: In this paper, a method for forming an active optical device, including the step of depositing an erbium-doped active core by sputtering, is presented, and the active core does not contain significant amounts of alkali metals or alkaline earth metals but does contain at least two modifier metals.
Abstract: An active optical device comprises a glass, waveguiding structure disposed on a substantially planar principal surface of a substrate. The structure includes a silica-based, erbium-doped active core. The active core has an absolute erbium concentration of at least about 0.5×1020 atoms per cubic centimeter, and a radiative lifetime of the erbium lasing level of at least about 5 milliseconds. The active core does not contain significant amounts of alkali metals or alkaline earth metals but does contain at least two modifier metals. Also disclosed is a method for forming an active optical device, including the step of depositing an erbium-doped active core by sputtering.

93 citations


Journal ArticleDOI
TL;DR: In this article, a sensor based on the temperature dependant behavior of the two lines of green emission of the erbium ion was proposed, which is self-calibrated.
Abstract: We propose a sensor based on the temperature dependant behavior of the two lines of green emission of the erbium ion. The ratio of the intensities of these two lines presents a very low dependance on pump wavelength and pump power fluctuations. The sensitivity of the ratio is 0.013//spl deg/C between room temperature and 600/spl deg/C. In addition, the measurement is self-calibrated. >

83 citations


Journal ArticleDOI
TL;DR: In this article, an erbium cascade laser in a fluorozirconate fiber is reported to achieve an output power of 158 mW, limited only by the 1.43 W power available from the Ti:sapphire pump laser.
Abstract: We report on an erbium cascade laser in a fluorozirconate fiber. Lasing on the transition 4I11/2 -> 4I13/2 at 2.71 µm is supported by colasing on the transition 4S3/2 -> 4I9/2 at 1.72 µm. This recycles the excitation that is lost via excited-state absorption and avoids the saturation of the output power. Threshold at 2.71 µm is 33 mW launched pump power at 791 nm. The measured slope efficiency of 22.6% is relatively close to the 29.1% stokes-efficiency limit. An output power of 158 mW is obtained, limited only by the 1.43 W power available from the Ti:sapphire pump laser. Output power is 15 and slope efficiency 2.5 times higher than reported in previous publications.

81 citations


Journal ArticleDOI
TL;DR: Erbium photoluminescence at room temperature and at 77 K has been observed from porous silicon doped with erbium from a spin-on silica gel film.
Abstract: Erbium photoluminescence at room temperature and at 77 K has been observed from porous silicon doped with erbium from a spin‐on silica gel film. Erbium incorporation into silicon dioxide at the surface of porous silicon and rapid thermal processing at temperatures higher than 1223 K were found to be a necessary prerequisite for erbium‐related luminescence in porous silicon. No erbium diffusion into monocrystalline silicon from the spin‐on films was observed. The depth‐dependent erbium concentration in the bulk of porous silicon was determined by secondary‐neutral‐ and secondary‐ion‐mass spectrometry depth profiling. The laterally resolved erbium distribution in the porous silicon was derived from energy‐dispersive x‐ray analysis. Possible mechanisms of erbium‐related luminescence in porous silicon are discussed.

80 citations


Journal ArticleDOI
TL;DR: A coupled system of the Hirota equation and the Maxwell-Bloch equations to describe the wave propagation in an erbium doped nonlinear fiber with higher order dispersion is proposed and the coupled system is found to allow soliton-type propagation.
Abstract: We propose a coupled system of the Hirota equation and the Maxwell-Bloch equations to describe the wave propagation in an erbium doped nonlinear fiber with higher order dispersion. The Painlev\'e property of the same is analyzed and the coupled system is found to be integrable. The Lax pair is also constructed and the single-soliton solution is explicitly shown. The coupled system is found to allow soliton-type propagation.

79 citations


Journal ArticleDOI
TL;DR: In this paper, the cathodoluminescence of erbium and oxygen coimplanted GaN(GaN:Er:O) and sapphire (sapphire:Er :O) was studied as a function of temperature.
Abstract: The cathodoluminescence(CL) of erbium and oxygen coimplanted GaN(GaN:Er:O) and sapphire (sapphire:Er:O) was studied as a function of temperature. Following annealing, the 1.54 μm intra‐4f‐shell emission line was observed in the temperature range of 6–380 K. As the temperature increased from 6 K to room temperature, the integrated intensity of the infrared peak decreased by less than 5% for GaN:Er:O, while it decreased by 18% for sapphire:Er:O. The observation of minimal thermal quenching by CL suggests that Er and O dopedGaN is a promising material for electrically pumped room‐temperature optical devices emitting at 1.54 μm.

68 citations


Journal ArticleDOI
TL;DR: In this article, the effect of high concentration and clustering on the performance of erbium-doped silica waveguide amplifiers is numerically investigated by combining Runge-Kutta and full-vectorial finite element methods.
Abstract: Effects of high concentration and clustering on the performance of erbium-doped silica waveguide amplifiers are numerically investigated. The model, based on propagation-rate equations of a laser system containing isolated ions and ion-pairs, is numerically solved by combining Runge-Kutta and full-vectorial finite-element methods; it allows the description of both uniform and pair-induced upconversion mechanisms. Numerical results show that cooperative upconversion processes seriously deteriorate amplifier performance at high erbium concentration. Moreover, we show that only the detrimental effect due to uniform upconversion can be reduced by a careful design of waveguide geometry and refractive index profile; performance degradation due to clustering may only be overcome by reducing the fraction of ions in pair using suitable codopants. The proposed model is validated with published experimental results. >

Journal ArticleDOI
TL;DR: In this paper, room temperature electroluminescence at 1.54 μm is demonstrated in erbium-implanted oxygen-doped silicon (27 at. % O), due to intra−4f transitions of the Er3+.
Abstract: Room‐temperature electroluminescence at 1.54 μm is demonstrated in erbium‐implanted oxygen‐doped silicon (27 at. % O), due to intra‐4f transitions of the Er3+. The luminescence is electrically stimulated by biasing metal‐(Si:O, Er)‐p+ silicon diodes. The 30‐nm‐thick Si:O, Er films are amorphous layers deposited onto silicon substrates by chemical‐vapor deposition of SiH4 and N2O, doped by ion implantation with Er to a concentration up to ≊1.5 at. %, and annealed in a rapid thermal annealing furnace. The most intense electroluminescence is obtained in samples annealed at 400 °C in reverse bias under breakdown conditions and it is attributed to impact excitation of erbium by hot carriers injected from the Si into the Si:O, Er layer. The electrical characteristics of the diode are studied in detail and related to the electroluminescence characteristics. A lower limit for the impact excitation cross section of ≊6×10−16 cm2 is obtained.

Journal ArticleDOI
TL;DR: In this article, a planar, single-transverse-mode waveguide laser has been fabricated in erbium-ytterbium codoped silicate glass using potassium ion exchange, which operates at 1536.8 nm, has a slope efficiency of 5.5%, and exhibits a launched power threshold of 14.8 mW when pumped at 966.6 nm.
Abstract: A planar, single-transverse-mode waveguide laser has been fabricated in erbium-ytterbium codoped silicate glass using potassium ion exchange. The laser operates at 1536.8 nm, has a slope efficiency of 5.5%, and exhibits a launched pump power threshold of 14.8 mW when pumped at 966.6 nm.

Journal ArticleDOI
TL;DR: In this paper, the saturation of the 2.71 μm laser output power was investigated in an erbium doped ZBLAN single-mode fiber with an Er3+ concentration of 5000 ppm mol.

Journal ArticleDOI
TL;DR: In this paper, the first integrated optical DBR waveguide laser with dry-etched Bragg grating was demonstrated in Er-diffusion-doped doped zeta -cut LiNbO/sub 3/ with Ti-diffused waveguide.
Abstract: The first integrated optical DBR waveguide laser with dry-etched Bragg grating (345 nm period) is demonstrated in Er-diffusion-doped doped zeta -cut LiNbO/sub 3/ with Ti-diffused waveguide. Three different resonator configurations have been investigated. The best device has a threshold of 40 mW coupled pump power ( lambda /sub p/=1484 nm) and emits up to 2 mW CW output power at lambda /sub s/=1531 nm with a typical bandwidth of 3.6 GHz.

Journal ArticleDOI
TL;DR: In this article, a single-frequency unidirectional erbium fiber ring laser operating at 1.55 /spl mu/m was reported, which uses an intracavity phase-shifted fibre Bragg grating as an ultranarrow frequency bandpass filter.
Abstract: The authors report a single-frequency unidirectional erbium fibre ring laser operating at 1.55 /spl mu/m which uses an intracavity phase-shifted fibre Bragg grating as an ultranarrow frequency bandpass filter. The linewidth of the laser was measured to be <2.0 kHz.

Journal ArticleDOI
TL;DR: The first observation of optical properties of new rare-earth-doped vitreous fluoride waveguides has been recently reported in this article, where they have been deposited by a physical vapour deposition technique on fluoride substrates.
Abstract: The first observation of optical properties of new rare-earth-doped vitreous fluoride waveguides has been recently reported. These vitreous fluoride films have been deposited by a physical vapour deposition technique on fluoride substrates. Several PZG films and sandwiches deposited on various substrates have been prepared with thickness of a few μm and doped in the guiding layer by various amounts of erbium and other rare-earth ions. High δn/n (10−2) has been achieved as a result of the glass compositions. Infrared as well as green and blue upconversion pumped fluorescences have been recorded under side light injection.

Journal ArticleDOI
TL;DR: In this paper, a harmonically mode-locked erbium fiber ring laser is described and the performance of transform-limited pulses with durations of 20-50 ps at 5.044 GHz repetition rate is obtained, where the laser is actively stabilized by locking intra-cavity Fabry-Perot etalon passbands to the laser modes.
Abstract: We describe the performance of a harmonically mode-locked, erbium fiber ring laser. Transform-limited pulses with durations of 20-50 ps at 5.044 GHz repetition rate are obtained. The modulation frequency can be detuned by up to /spl plusmn/70 kHz and the lasing wavelength can be varied over the entire erbium gain bandwidth. Pulsewidths and pulse bandwidths are measured as a function of modulation power and frequency detuning. The laser is actively stabilized by locking intra-cavity Fabry-Perot etalon passbands to the laser modes. >

Journal ArticleDOI
TL;DR: Continuous and discrete single-frequency tuning in the 1.5-μm wavelength region are demonstrated by incorporation of erbium:ytterbium phosphosilicate fibers in single and compound fiber Fabry–Perot cavity configurations.
Abstract: Continuous and discrete single-frequency tuning in the 1.5-μm wavelength region are demonstrated by incorporation of erbium:ytterbium phosphosilicate fibers in single and compound fiber Fabry–Perot cavity configurations. Continuous wavelength tuning was obtained over 3.3 nm in a single-cavity laser of 218-μm cavity length. Discrete wavelength tuning was achieved over 9.59 nm in a compound-cavity laser having a 2-mm gain section.

Journal ArticleDOI
TL;DR: In this paper, the 1.7µm excited state absorption spectrum in erbium doped glasses was obtained by measuring the gain of a waveguide in the 1400-1800 nm region.
Abstract: We have measured, for the first time, the complete 1.7µm excited state absorption spectrum in erbium doped glasses. The spectrum is obtained by measuring the gain of an erbium doped waveguide in the 1400-1800 nm region. Using the measured spectra, we estimate the 1.5µm uniform upconversion rate by calculating the spectral overlap between the 1.5µm emission and 1.7µm ESA cross sections. The technique is applied to erbium-doped, ion-exchangeable silicate glasses, yielding upconversion constants in the range of 1-10 x 10 -18 cm 3 /s.

Journal ArticleDOI
TL;DR: In this article, a novel configuration of an erbium-doped-fiber optical output-limiting amplifier (OLA) is presented which is realized by simply introducing a differential lump-loss between the signal and the pump power at a particular point along the fiber.
Abstract: A novel configuration of an erbium-doped-fiber optical output-limiting amplifier (OLA) is presented which is realized by simply introducing a differential lump-loss between the signal and the pump power at a particular point along the fiber. The OLA exhibits an input-power dynamic range in excess of 40 dB and the capacity to control optically the level of the constant-output signal. >

Journal ArticleDOI
TL;DR: In this paper, the mechanisms that lead to room-temperature continuous-wave green upconversion lasing in Er3+:LiYF4 are investigated in computer simulations.
Abstract: In computer simulations the mechanisms that lead to room-temperature continuous-wave green upconversion lasing in Er3+:LiYF4 are investigated. The rate-equation system considers the full erbium level scheme up to 2H9/2, ground-state depletion, excited-state absorption on the pump and laser wavelengths, three interionic processes, stimulated emission, and the crystal and resonator data of the experiments. Experimental results performed at the University of Hamburg, Germany, are reproduced in the simulation. The influence of different parameters as pump wavelength, absorption cross sections, interionic parameters, dopant concentration, and temperature is investigated. An avalanche effect which exploits the strong cross relaxation from the upper laser level and the upconversion from 4I13/2 leads to an efficient population of the upper laser level. At higher dopant concentrations the cross relaxation becomes detrimental to stimulated emission due to the depletion of the upper laser level. This concentration dependence can be considered as a general behavior of rare-earth-doped avalanche lasers.

Patent
08 May 1995
TL;DR: In this article, a plano-concave resonator consisting of a concave high reflector, a flat output coupler, a Er:YAG crystal and a YAG intracavity etalon is used as the tuning element.
Abstract: A discrete-element Er:YAG laser, side pumped by a 220 Watt peak-power InGaAs diode array, generates >500 mWatts at 2.94 μm, and is tunable over a 6 nm range near about 2.936 μm. The oscillator is a plano-concave resonator consisting of a concave high reflector, a flat output coupler, a Er:YAG crystal and a YAG intracavity etalon, which serves as the tuning element. The cavity length is variable from 3 cm to 4 cm. The oscillator uses total internal reflection in the Er:YAG crystal to allow efficient coupling of the diode emission into the resonating modes of the oscillator. With the tuning element removed, the oscillator produces up to 1.3 Watts of average power at 2.94 μm. The duty factor of the laser is 6.5% and the repetition rate is variable up to 1 kHz. This laser is useful for tuning to an atmospheric transmission window at 2.935 μm (air wavelength). The laser is also useful as a spectroscopic tool because it can access several infrared water vapor transitions, as well as transitions in organic compounds. Other uses include medical applications (e.g., for tissue ablation and uses with fiber optic laser scalpels) and as part of industrial effluent monitoring systems.

Journal ArticleDOI
TL;DR: In this article, the possibility of soliton-type pulse propagation in an erbium doped nonlinear optical fiber system with inhomogeneous core medium has been investigated and the Painleve analysis of the system equation is explicitly shown.

Journal ArticleDOI
TL;DR: The principle of a high-dynamic, quasi-distributed temperature sensor based on the behavior of the 1.13- and the1.24-µm emission lines in erbium-doped silica fibers is proposed, with power and wavelength pump variations permitting the realization of self-calibrated quasi- Distributed sensors.
Abstract: We propose the principle of a high-dynamic, quasi-distributed temperature sensor based on the behavior of the 1.13- and the 1.24-μm emission lines in erbium-doped silica fibers. The ratio of fluorescent intensity of these lines presents a temperature dynamic of more than 11 dB between room temperature and 600 °C. As the lower level of these transitions is not the fundamental, the emission lines are absorption free, and no dependence of the intensity ratio of the two lines has been observed, with power and wavelength pump variations permitting the realization of self-calibrated quasi-distributed sensors.

Journal ArticleDOI
TL;DR: In this paper, the erbium was used as an optically active center (ErO6) through the use of metal-organic dopant sources and the characteristic 1.5 μm emission was observed by photoluminescence.
Abstract: Epitaxial growth of erbium‐doped silicon films has been performed by plasma‐enhanced chemical vapor deposition using an electron‐cyclotron‐resonance source. The goal was to incorporate erbium as an optically active center (ErO6) through the use of metal‐organic dopant sources. The characteristic 1.5 μm emission was observed by photoluminescence. Chemical analysis of the film revealed, however, that the organic ligands were decomposing and contributing to the carbon contamination of the films. Analysis of the molecular flux to the substrate indicated that the metal‐organic compound used, tris(2,2,6,6‐tetramethyl‐3‐5‐heptanedionato)erbium(III), was most likely to decompose, and supply unbonded atomic erbium and not the optical active species, ErO6. Excessive carbon contamination lowered epitaxial quality and reduced the photoluminescent intensity. Photoluminescent intensity was improved by a 600 °C anneal but was strongly quenched by a 900 °C anneal. The low‐temperature anneal improved crystal quality, and ...

Journal ArticleDOI
TL;DR: In this paper, Nanocrystalline germanium films containing erbium were deposited by thermal evaporation under 0.6 Torr of argon onto crystalline silicon wafer substrates.
Abstract: Nanocrystalline germanium films containing erbium were deposited by thermal evaporation under 0.6 Torr of argon onto crystalline silicon wafer substrates. Weak broad photoluminescence (PL) around 1.5 μm was observed at room temperature. Annealing under 10−7 Torr of vacuum for 3 h at 500 °C produced no change in the PL spectrum. After 1 h oxidation in air at 500 °C the PL intensity increased by an order of magnitude with reduction of the spectral linewidth and appearance of distinct structures, a portion of which is similar to that observed for Er‐implanted Si:O. Subsequent increase in oxidation time reduced the PL intensity slightly with no change in the spectral shape. The PL intensity exhibits a sublinear increase with pump power and approaches saturation at 200 mW. Raman spectra before and after anneal are also presented. Annealing increased the average grain size from 5 to 10 nm. The PL spectrum of erbium metal after oxidation in air at 500 °C is quite different from that of these oxidized Ge:Er films.

Journal Article
TL;DR: In this article, a passive channel equalizer using a twin-core EDFA is studied in detail, which relies on the spatial separation of the different channels provided by the twin core geometry and the power-dependent differential gain saturation given by the erbium ions.
Abstract: A passive channel equalizer using a twin-core EDFA is studied in detail. It relies on the spatial separation of the different channels provided by the twin-core geometry and the power-dependent differential gain saturation given by the erbium ions. The amount of channel equalization depends on the fiber geometry parameters, as well as the optical parameters and relative channel power. In the two-channel case, gain saturation limits the useful channel input powers into the range of ∼-20 dBm to ∼0 dBm. Channel equalization rates in excess of -0.4 dB per dB of input-power imbalance are predicted. When used in cascade, twin-core EDFA's are shown to provide not only efficient channel-power stabilization, but also self-healing against additional channel losses

Journal ArticleDOI
K.R. Huffman1, K. DeLapp1, H. Andrews1, P. Sprinkle1, M. Nickels1, B. Norris1 
TL;DR: In this article, the absorption and emission spectra of fullerenes doped with erbium and nickel were measured in the 1.5 μm region when excited by an argon ion laser.

Patent
03 Oct 1995
TL;DR: In this article, rare earth doped ferroelectric materials are disclosed as reversible holographic recording medium (25) for use in two-photon recording systems, which do not require high-power, short pulse length, mode-locked or Q-switched lasers.
Abstract: Rare earth doped ferroelectric materials are disclosed as reversible holographic recording medium (25) for use in two-photon recording systems. Such rare earth elements provide long-lived electronic states intermediate the ferroelectric material's valence and conduction bands. In some cases, these rare earth intermediate states have a sufficiently long life that low-power continuous wave ('cw') lasers (1) can be used to record interference patterns on them. Thus, two-photon holographic recording systems are also disclosed which do not require high-power, short pulse length, mode-locked or Q-switched lasers. Rather, the disclosed holographic recording systems employ cw lasers such as diode lasers. The rare earth dopants include praseodymium, neodymium, dysprosium, holmium, erbium, and thulium. These dopants provide ions having 4f excited states that give rise to absorptions in the near infra-red and visible spectral regions and typically have lifetimes on the order of 0.1 to 1 milliseconds. The disclosed two-photon holographic recording systems provide for absorption of a first photon which excites electrons of a holographic recording medium to a rare-earth intermediate state. Thereafter, upon absorption of a second photon, the electrons are promoted to the medium's conduction band where they are arranged according to the interference pattern provided by the recording system.