Showing papers on "Erbium published in 1987"

Low-noise erbium-doped fibre amplifier operating at 1.54μm

Abstract: High gain amplification of up to 28 dB has been observed in a 3m-long erbium-doped fibre. The amplifier has a spectral bandwidth of greater than 300GHz in the region of 1.536µm and a measured sensitivity of -42dBm at a bit rate of 140 Mbit/s.

High-gain erbium-doped traveling-wave fiber amplifier

Abstract: Traveling-wave amplification of a lambda = 1.53 microm signal with +22-dB gain is achieved at 295 K in an Er(3+)-doped single-mode fiber using a lambda = 514.5 nm pump source. The optimum fiber length for maximum gain is determined experimentally. A limit in signal-to-noise ratio that is due to concurrent amplification of spontaneous emission is observed. By cooling the fiber to 77 K, the amplifier gain is increased to +29 dB as a result of depopulation of the lower laser level.

Erbium doping of molecular beam epitaxial GaAs

Abstract: The doping of molecular beam epitaxial GaAs with erbium up to a concentration of 2×1019 cm−3 has been successfully demonstrated. Up to a concentration of about 5×1018 cm−3 the surface morphology remained good but for higher doping levels the surface became structured. Hall and profile measurements indicate that erbium doping gives rise to a trapping level capable of compensating silicon‐doped layers. For the first time photoluminescence from a rare earth element incorporated in a III‐V semiconductor has been observed at room temperature.

Incorporation of erbium in GaAs by liquid-phase epitaxy

Abstract: The incorporation of the lanthanide element erbium in GaAs during growth by liquid‐phase epitaxy is investigated by low‐temperature photoluminescence measurements. After an anneal of the epitaxial layers at 850 °C, a characteristic Er‐associated optical transition appears at a wavelength of ∼1.55 μm, however, no erbium‐related photoluminescence signal is found in the as‐grown GaAs:Er layers. The Zeeman splitting of the new photoluminescence lines reveals a cubic symmetry of the optically active Er complex. Successive mechanical polishing and annealing of the layers provides evidence for the incorporation of Er within the layer as an optically inactive Er complex, which is activated only at the surface by thermal annealing.

Er‐doped InP and GaAs grown by metalorganic chemical vapor deposition

Abstract: Erbium is doped into InP and GaAs epitaxial layers for the first time by metalorganic chemical vapor deposition using tris‐cyclopentadienyl erbium [Er(C5H5)3]. Uniform doping as high as 1.5×1019 cm−3 across the entire depth of the epitaxial layers is revealed by secondary ion mass spectroscopy. Erbium‐related photoluminescence spectra around 1.54 μm from InP:Er and GaAs:Er show remarkable resemblance. At 2 K, in addition to the dominant zero phonon line at 1542 nm for InP:Er and at 1543 nm for GaAs:Er, several other zero phonon lines are observed at longer wavelengths. The Er‐related peak is observed at 1539±1 nm even at 300 K for InP:Er, shifting toward the shorter wavelengths by a little as 3 nm with increasing temperature from 2 to 300 K.

Optical fibre lasers and amplifiers

Abstract: This thesis describes the development and characterisation of single-mode optical fibre lasers and amplifiers. Although the fibre laser configuration was first employed over twenty years ago, its application to conventional optical fibre technology has not been demonstrated previously. The new devices are based on single-mode fibres doped with rare-earth ions, notably neodymium and erbium. The combination of strong absorption bands, long fluorescence lifetimes; low fibre losses in the infra-red and small fibre cores have made possible very low threshold and efficient fibre lasers. Experiments on the tunability, output spectra and pulsed operation of these devices are described. A number of world firsts, including the Lowest, threshold and widest tuning range of a doped glass laser, and the efficient CW operation of an erbium-doped three level laser, have been achieved. High-gain amplification at 1.54µm, the preferred wavelength for optical communication, has also been demonstrated. The results have been modelled by adapting conventional laser theory to the single-mode fibre configuration, and some simple design criteria are considered.

Single longitudinal mode operation of Er‐doped 1.5‐μm InGaAsP lasers

Abstract: We attribute the single longitudinal mode operation of some Er‐doped 1.5‐μm InGaAsP lasers, observed here, to inhomogeneities in the active layer resulting from the Er. These results do not rule out the possibility of gain narrowing by the Er when Er is properly incorporated in the active layer.

Low-threshold CW operation of an erbium-doped fibre laser pumped at 807 nm wavelength

Abstract: We report an erbium-doped fibre laser operating CW at a wavelength of 1555nm pumped at a wavelength of 807 nm, with a threshold launched pump power of 2.5 mW. This level corresponds to only 1 mW of pump power absorbed.

Magnetic phase transitions in nanocrystalline erbium

Abstract: Nanocrystalline samples of 99.9% pure erbium with particle sizes between 10 and 70 nm have been produced by the inert gas condensation technique. Magnetic susceptibility measurements on samples compacted to between 50% and 75% of bulk density indicate a modification in the high‐temperature phases and superparamagnetic behavior at low temperatures. ESR signals near g=10 are probably due to Er compounds which may form during the production process.

Power limits of a YAG:Er laser

Abstract: The power limits of a repetitively Xe-flashlamp pumped YAG: Er laser with 40% at % dopant concentration, have been determined. The limits result from thermal effects. These limits as well as the threshold can be reduced by selective pumping of the 4I 11 2 upper laser level.

Bandwidth-limited picosecond pulses from a YSGG:Cr3+:Er3+ laser (λ=2.79 µ) with active mode locking

Abstract: Ultrashort λ=2.79 µ pulses were generated in an yttrium scandium gallium garnet crystal laser activated with chromium and erbium. Active mode locking and synchronous electrooptic modulation of the resonator losses were used. The duration of bandwidth-limited (τΔν≈0.5) single laser pulses selected from a train could be varied in discrete steps by intracavity spectral selectors within the range 40–220 psec (repetition frequency 1 Hz). Continuous tuning of the emission spectrum of the laser was possible within a range of 1 cm−1 near the center of the gain profile. When the energy of a single spike was 4 mJ ( in a four-pass amplifier) and the pulse duration was τ = 40 psec, the power of the laser radiation in the form of the TEM00 mode was 100 MW.

Nondiffusion and 1.54 μm luminescence of erbium implanted in InP

Abstract: Erbium impurities were implanted in indium phosphide. The Er depth distributions are given for nonannealed and annealed substrates. It is shown that erbium has a very small diffusion coefficient, if any, in InP. The photoluminescence spectra show, after annealing at high temperature, the main erbium emission centred at 1.536μm. This emission is stronger after annealing at 700°C. Our results are the first evidence showing l.54μm emission at room temperature.

Electron spin resonance of erbium in gallium arsenide

Abstract: Electron spin resonance (ESR) has been detected for erbium, Er(4f11), in gallium arsenide The ESR spectrum was found to be isotropic, with a hyperfine splitting of A(167Er)=208*10-4 cm-1 and a g-factor of g=5921 The magnitude of the latter is compatible with a Gamma 7(T4) ground state, as expected for a substitutional ErGa(4f11):GaAs defect

Rare earth doped semiconductor laser

Abstract: A solid state laser is disclosed wherein a semiconductor active layer is arranged in a Fabry-Perot cavity and the active layer is doped with a rare earth ion having a dominant emission wavelength. The proportion of elements for the compound active layer is chosen such that the bandgap corresponds to a wavelength which is longer than the emission wavelength of the rare earth ion. In the specific embodiment disclosed, the quarternary semiconductor compound is gallium indium arsenide phosphide and the rare earth ion is erbium.

Distributed temperature sensor using holmium doped optical fibre

Abstract: Preliminary results of an optical-fiber distributed temperature sensor using neodymium as the active fiber dopant have been reported. An investigation has been made of fibers doped with the rare earths neodymium, erbium, praseodymium, and holmium which were fabricated using the method previously reported. Silica fiber doped with holmium has an order of magnitude greater temperature sensitivity than the other rare earths. The sensitivity of the absorption to temperature is thought to be due to a satellite band on the long-wavelength side of the main absorption bands, as shown in the attenuation plots in Fig 1. Thermal population at this energy level causes the attenuation to increase rapidly with temperature.

Spectroscopy of 3‐μm laser transitions in YAlO3:Er

Abstract: The spectroscopic properties of the 3 μm emission of a YAlO3:Er laser have been investigated. Erbium crystals with dopant concentrations of 10 %, 20 % and 50 % have been used in the experiments. The emission of YAlO3 crystals is strongly dependent on the crystal orientation with respect to the polarization of the laser light. The polarization dependence of the most prominent emission lines has been measured for laser crystals oriented with their axes along the crystallographic a- and b- directions. An example is shown in Fig. 1.

Laser-Tissue/Water Interaction Of The Erbium 2.9 Pm Laser

Abstract: The trivalent Erbium transition, 4 T 11/2 4[/supI 13/2 has an emission wavelength close to , 3 μm in a variety of host laser crystals. The fundamental 0-H vibrational stretch in water occurs at approximately the same wavelength. It is therefore expected that the absorption coefficient of water near 3 μm would be of the order of 10 4 cm -1 . In order to measure this value precisely with a transmission spectrometer, it is necessary to have a film with a thickness of the order of the reciprocal of the absorption coefficient of water. This implies a thin film of water of about one micron. It is also desirable to measure the water absorption coefficient in the infrared out to wavelengths as long as 12 μm. This would require cell thicknesses up to 20 μm. A special cell has been designed and constructed to meet these criteria of variable thickness, IR transmission and compatibility with high purity water samples. The cell is shown in cross section in Figure 1. It is designed to provide a variable thickness film of water and a liquid filled space adjacent to the film that acts as a reservoir. The IR transparent ZnSe windows are attached to the Invar holders which are separated by two Teflon gaskets and a Invar spacer with inflow and outflow ports. The two Invar holders are squeezed together, compressing the Teflon gaskets. This not only changes the film thickness, but provides a positive seal with the gaskets. The film thickness is adjusted to the desired value, the transmission of the water film is measured and the film thickness is verified after the transmission measurement. The sequence can then be repeated for different thicknesses of the cell.

Infrared light emitting diode

Abstract: PURPOSE:To unify a monolithic by a method wherein silicon is used as a principal active substance, an active region related to light emission consists of a PIN junction, a P-N junction or a Schottky junction, the inside of the active region contains trivalent erbium atoms and a specific emission wavelength is formed. CONSTITUTION:The title light emitting diode represents a light-emitting diode consisting of an silicon crystal and having a PIN junction composed of a P layer 1, an I layer 2 and an N layer 3, and the I region 2 having thickness of approximately 1mum contains approximately 1mol% trivalent erbium atoms. The formation of the PIN junction having such a composition can be grown effectively through an ion implantation method or a molecular beam epitaxial method. When reverse bias voltage is applied to the PIN junction and an electric field is generated in the I region 2, an electron avalanche is generated in the I region 2, and the partial energy of the electron avalanche is transmitted over erbium atoms by collision excitation. Even when a P-N junction or a Schottky junction is utilized in place of the PIN junction, approximately the same effect can be expected. Accordingly, a 1.5mum light source capable of being unified with an silicon integrated circuit and easy to be manufactured can be acquired.

Addition of optical frequencies by cooperative processes

Abstract: The conversion of pumping radiation from erbium (lambda/sub l/ = 1.54 ..mu..m) and neodymium (lambda/sub l/ = 1.054 ..mu..m) lasers to the visible spectrum with lambda/sub l/ = 0.67 ..mu..m has been obtained for the BaYb/sub 2/F/sub 8/:Er (0.1%) crystal. It is shown that by adding the optical frequencies of the /sup 4/F/sub 9//sub ///sub 2/(Er) levels one can pump more efficiently than when using the anti-Stokes conversion of 1.054-..mu..m radiation.

Semiconductor laser luminous flux detection panel

Abstract: PURPOSE:To enable the inspection of infrared rays with 1.5mum range, by providing glass-like ceramic sheet dispersed with a specified amount of erbium as fluoride on a substrate for reflecting infrared rays. CONSTITUTION:A sheet 2 in which erbium equivalent to 8-80% of all cations is dispersed as fluoride into a glass composed of a mixture of GeO2 and PbF2 or the like is applied on a substrate 1, for example, copper plate for reflecting infrared rays. When the amount of erbium in the sheet 2 is under 8%, conversion efficiency for 1.5mum light is too low while when it exceeds 80%, it will be impossible to fill a clearance between crystals with glass. The use of the sheet 2 containing erbium of said range as a detection panel elevate the infrared rays visibility conversion efficiency, thereby enabling the detection of infrared rays with 1.5mum range.

FLUORESCENCE DYNAMICS IN ERBIUM AND HOLMIUM DOPED YLiF4

Abstract: The fluorescence dynamics at room temperature was studied through an analysis of the fluorescence decay times of the various excited states emitting in the visible and in the infrared ranges. The optical processes are described in terms of rate equations and appropriate models are proposed to fit the time dependent intensity of the different fluorescences.

Upconversion Pumped Laser at 1.73 µm in Er:LiYF4 at Room Temperature

Abstract: Using excitation via an upconversion process to populate the upper laser level, laser emission at 1.73 μm from the 4S3/2 → 4I9/2 transition has been observed in 4% and 8% Er:LiYF4 (Er:YLF) at room temperature. Laser emission at 1.68 μm from the erbium 4I9/2 → 4I13/2 transition was also observed in both samples.

Spectroscopy of the 3 μ m Laser Transitions in YAlO 3 :Er

Abstract: The spectroscopic properties of the 3 μm emission of a YAlO3:Er laser have been investigated. Erbium crystals with dopant concentrations of 10 %, 20 % and 50 % have been used in the experiments. The emission of YAlO3 crystals is strongly dependent on the crystal orientation with respect to the polarization of the laser light. The polarization dependence of the most prominent emission lines has been measured for laser crystals oriented with their axes along the crystallographic a- and b- directions. An example is shown in Fig. 1.

Single longitudinal mode output from a fox-smith erbium fibre laser

Abstract: Erbium fibre lasers can demonstrate low-threshold power lasing at around 1.55 μm with a tuning range exceeding 50 nm in the important low loss telecommunications window1.

Analysis of the Spectra of Triply Ionized Iron in Rare-Earth Aluminum Garnets.

Abstract: : Recent successes in transferring energy from excited chromium ions to neodymium ions in gadolinium scandium gallium garnets have increased interest in the spectra of transition-metal ions in potential laser host materials. In particular, the garnet materials, which can be doped with both rare-earth and transition-metal ions, are possible candidates for such a laser. In the work reported here, we analyze the spectra of Ferric ions in the rare earth aluminum garnets, Gad, Terbium, Oysprosium, Hofmium ions, Erbium, Thullium and Ytterbium. The Fe3+ ion is assumed to occupy the site with Cubic symmetry. The reported analysis of the experimental data assumes cubic symmetry and gives the usual parameters for the free ion and the crystal field. Using the known crystallographic data we then compute the crystal field components. The concept of rotational invariance is used to obtain an estimate of the radial integrals needed to convert the crystal field components to the crystal field parameters. The resulting crystal field parameters are used to calculate the energy levels of Fe3+ in the entire series, including lutetium.