Showing papers on "Erbium published in 1996"

24-line multiwavelength operation of erbium-doped fiber-ring laser

Abstract: Simultaneous lasing at up to 24 wavelengths is demonstrated in an erbium-doped fiber-ring laser using a simple design. This result is achieved using a low-loss cavity, controlled polarization evolution and liquid nitrogen cooling to enhance spectral hole-burning, polarization hole-burning, and polarization selectivity. The design does not include any wavelength-selective components; instead, it utilizes wavelength selectivity provided by polarization evolution in the cavity. The amplitude variation between emission peaks is less than 3 dB over a 17-nm spectral range. A narrow linewidth of 0.15 nm, dense line spacing of 1.1 nm, and a good signal-to-noise ratio of more than 30 dB are achieved over most of the erbium bandwidth. The comb spectrum location and width are adjustable by changing and adjusting cavity components.

Multiwavelength erbium-doped fibre laser using intracavity etalon and cooled by liquid nitrogen

Abstract: The authors report simultaneous oscillation of 17 0.8 nm spliced wavelengths from a Fabry-Perot (FP) erbium doped fibre laser. Multiwavelength operation is made possible by inserting an intracavity etalon and cooling the erbium doped fibre at 77 K by liquid nitrogen. It is promising as the multiwavelength light source for wavelength division multiplexing (WDM) networks. Heterodyne measurement shows that two or three longitudinal modes exist in each wavelength.

Electroluminescence of erbium-doped silicon

Abstract: Recombination processes in rare-earth metals in semiconductors are a special case due to the localized nature of $f$ electrons. Our work explores in detail the radiative and nonradiative mechanisms of energy transfer for erbium in silicon by investigating the temperature dependence of the intensity and the decay time of the photoluminescence of Er-related centers in Si. We show that nonradiative energy back transfer from the excited Er $4f$ shell causes luminescence quenching below 200 K. We study electroluminescence decay by applying different bias conditions during the decay. In a two-beam experiment the photoluminescence decay is monitored for different background-excitation laser powers. Changes in the decay time are strong evidence of the impurity Auger effect as an efficient luminescence-quenching mechanism for Er in Si. A fast initial luminescence decay component at high pumping powers is related to quenching by excess carriers. The power dependence, the decay-time components, and the two-beam experiment are simulated by a set of rate equations which involve the formation of excitons, a decrease of the pumping efficiency by exciton Auger recombination, and a decrease of radiative efficiency by the impurity Auger effect with free electrons. As a nonradiative deexcitation path competing with spontaneous emission, the impurity Auger effect decreases the excited-state lifetime of Er in Si, and dominates the thermal quenching of luminescence in the temperature range from 4 to 100 K. We find that the decrease of emission intensity above 100 K is caused by an unidentified second back-transfer process.

10-ghz, 1.3-ps erbium fiber laser employing soliton pulse shortening

Abstract: An actively mode-locked single-polarization erbium fiber laser modulated at 10 GHz utilizes intracavity soliton formation to produce 1.3-ps pulses, well below the Kuizenga–Siegman limit, without passive mode locking. The observed degree of pulse shortening agrees with the predictions of recently developed soliton laser models. The pulse dropout ratio was measured to be less than 10−12, and the rms amplitude and phase jitter are less than 1.1% and 0.16 ps, respectively.

Electroluminescence of erbium–oxygen‐doped silicon diodes grown by molecular beam epitaxy

Abstract: We have fabricated erbium–oxygen‐doped silicon light emitting diodes with molecular beam epitaxy by simultaneously evaporating erbium and silicon and providing a suitable background pressure of oxygen. In reverse bias, the diodes show intense room‐temperature electroluminescence at λ=1.54 μm, originating from the intra‐4f transition of erbium. This luminescence does not show temperature quenching between 4 and 300 K. In forward bias the erbium peak intensity is reduced by a factor of 30 at low temperatures and shows temperature quenching.

80〜200 GHz erbium doped fibre laser using a rational harmonic mode-locking technique

Abstract: Pulse trains with repetition rates as high as 80~200 GHz were obtained at 1.55 µm, using rational harmonic mode-locking with an erbium doped fibre laser. A fundamental repetition frequency (fosc) of 40 GHz was first generated by applying a 40 GHz modulation frequency to an LN intensity modulator in the fibre cavity, in which the longitudinal mode spacing (Δf) was 1.5 MHz. By rationally detuning the modulation frequency by Δf/n, the authors succeeded in obtaining a repetitive oscillation of (nfosc+Δf). The maximum frequency was 200 GHz, at which n corresponds to 5.

Erbium incorporation in LiNbO3 by diffusion-doping

Abstract: The erbium incorporation into LiNbO3 by diffusion doping is investigated in detail by means of Secondary Ion Mass Spectrometry, Secondary Neutral Mass Spectrometry, Rutherford Backscattering, Atomic Force Microscopy, X-ray Standing Wave technique and optical site-selective spectroscopy. The diffusion of erbium in LiNbO3 can be described by Fick’s laws of diffusion with a concentration-independent diffusion coefficient. The diffusion constants and activation energies for Z-cut (X-cut) LiNbO3 are 4.8×10-5 cm2/s (12.0×10-5 cm2/s) and 2.28 eV (2.44 eV), respectively. A limited solubility of erbium in LiNbO3 has to be taken into account increasing exponentially with rising temperature. During the first step of diffusion an Er x Nb y -oxide layer is formed at the surface of the sample acting as diffusion reservoir. Erbium is incorporated into LiNbO3 on vacant Li-sites slightly shifted from the original Li-position along the (-c)-direction. Site-selective spectroscopy found four distinguishable energetically different erbium centres at this lattice site resulting from locally different symmetries of the crystal field.

Diode-pumped bulk erbium-ytterbium lasers

Abstract: A comprehensive review of the work done by our group, during the last few years, on diode-pumped cw operating bulk Er : Yb phosphate glass is presented. The high performance of this laser in terms of output power, laser slope efficiency, single longitudinal and transverse mode operation, laser tunability and frequency stability, amplitude noise, and active mode-locking operation, are considered. The combination of this high performance and potential low cost makes these laser devices attractive for a variety of applications including spectroscopy, metrology, optical radars, optical communications, and all optical switching.

High repetition rate erbium:YAG laser for tissue ablation

Abstract: A medical laser system is disclosed for ablating biological material. The system includes an Erbium:YAG gain medium capable of generating a pulsed output having a wavelength of 2.9 microns. The laser is optimized to generate a pulsed output having a repetition rate of at least 50 hertz and preferably at least 100 hertz. The output is delivered to the target tissue via an optical fiber. Preferably, a suction source is provided to aspirate the tissue as it is being ablated. The erbium laser system provides accurate ablation with minimal damage to surrounding tissue.

Intensity noise reduction in a single-frequency ytterbium-codoped erbium laser

Abstract: We report on intensity noise suppression in a diode-pumped, single-frequency erbium bulk-glass laser codoped with ytterbium. Using an optoelectronic feedback circuit, we acheived a 30-dB reduction of the relaxation oscillation peak, at 160-kHz frequency, to a relative intensity noise of −114 dB/Hz. A useful output power of 15 mW at 1533-nm wavelength was obtained.

Widely tunable single-frequency erbium-ytterbium phosphate glass laser

Abstract: A tunable, single‐frequency, diode‐pumped miniature Er:Yb:glass laser of high power is described. The laser exhibits two intervals of continuous tuning, from 1549 to 1563 nm (Δλ=14 nm) and from 1531 to 1540 nm (Δλ=9 nm), respectively. For an input pump power of 140 mW, a single frequency output power of 20 mW at 1563 nm has been obtained. The tuning characteristics are found to be strictly related to the gain–loss balance of the laser cavity.

Electroluminescence from erbium and oxygen coimplanted gan

Abstract: Room temperature operation of erbium and oxygen coimplanted GaN m‐i‐n (metal–insulator–n‐type) diodes is demonstrated. Erbium related electroluminescence at λ=1.54 μm was detected under reverse bias after a postimplant anneal at 800°C for 45 min in flowing NH3. The integrated light emission intensity showed a linear dependence on applied reverse drive current.

Efficiency of erbium 3-/spl mu/m crystal and fiber lasers

Abstract: The population dynamics of erbium 3-/spl mu/m crystal and fiber lasers are compared experimentally and theoretically. Laser slope efficiencies of 40% in Er:LiYF/sub 4/ and 23% in a fluorozirconate fiber are experimentally demonstrated under Ti:sapphire pumping. These are both to our knowledge the highest values reported so far for the different host geometries. On the basis of the excitation and loss mechanisms, the best pump wavelengths are determined to be 970 mm in LiYF4 and 791 nm in a fluorozirconate fiber. The theoretical limit of the slope efficiency with respect to absorbed pump power is redefined as depending on the major population mechanisms of the system. Calculated values are 56% in Er:LiYF4 and 27% in a fluorozirconate fiber.

Temperature and pressure effects during erbium laser stapedotomy.

Abstract: BACKGROUND AND OBJECTIVES Laser-assisted stapedotomy has become a well-established alternative to the mechanical drilling method. The goal of this study is to quantify the mechanical and thermal tissue effects and to determine optimum erbium laser parameters for safe clinical treatment. STUDY DESIGN/MATERIALS AND METHODS On an inner ear model, time-resolved pressure measurements and Schlieren optical flash photography were performed during the perforation of the stapes foot plate using an erbium laser at 2.79 microns. The laser radiation was transmitted via an optical zirconium fluoride fiber. The laser-treated foot plates were investigated by light microscopy and scanning electron microscopy to visualise the laser-induced tissue effects. RESULTS Perforation of the stapes foot plate can be performed with a few erbium laser pulses with high precision and a thermal damage zone of < 10 microns. Strong pressure transients were found to be generated by the bone ablation process and the collapse of a vapor channel created in the perilymph after fenestration. CONCLUSION From the comparison of the laser-induced pressure with the limit graph to avoid hearing defects published by Pfander, an unobjectionable use of the erbium laser is deduced for fluences < 10 J/cm2. The erbium laser seems to represent an ideal instrument for middle ear surgery with all the advantages (precision, fiber optic transportable, high ablation efficiency, safety) desired for clinical application.

Optimization of an Er-doped silica glass optical waveguide amplifier

Abstract: The optical gain performance of a highly Er-doped waveguide amplifier is affected by concentration quenching and cooperative upconversion effects. Based on materials parameters, which were previously determined for Er-doped sodalime-silicate glass, we calculate how the gain performance can be improved by reducing these limiting processes. For amplifiers with an Er concentration exceeding 0.1 at.%, the Er dc-excitation rate is dominated by cooperative upconversion rather than radiative decay or nonradiative decay due to coupling to defects. The effect of lowering the waveguide loss and reducing the optical mode diameter is also demonstrated.

Local structure and 1.5 μm quantum efficiency of erbium doped glasses for optical amplifiers

Abstract: The Judd-Ofelt intensity parameters, local structure and 1.5 μm luminescence characteristics of Er 3+ ions were investigated in silicate glasses with the composition of (75 − x)SiO 2 · xAlO l3/2· 25NaO 1/2 · 0.5 ErO l3/2 with various aluminum contents. Radiative decay rate from the 4 I 13/2 level was determined by Judd-Ofelt analyses, and non-radiative decay rate was obtained combined with the lifetime measurement. With increasing Al 2 O 3 content, the multiphonon decay rate decreased, which almost corresponded to the energy shift observed in the phonon sideband spectra, whereas the emission probability of 4 I 13/2 → 4 I 15/2 increased. Accordingly, the quantum efficiencies of the 1.5 μm emission were enhanced from 50% to almost 90%. The results are discussed in terms of the change in the local structure and orbital electron density of Er 3+ ions with the structural evolution of the glass.

10 GHz, 2ps regeneratively and harmonically FM mode-locked erbium fibre ring laser

Abstract: A 10 GHz regeneratively and harmonically FM mode-locked erbium fibre ring laser is reported for the first time. The output pulse width is 2 ps and the spectral width is 1.4 nm, resulting in a time bandwidth product of 0.34. The output pulse is almost transform limited, despite the FM mode-locking. This can be attributed to the anomalous group velocity dispersion which compensates for the up-chirping. The down-chirping does not evolve into stable FM mode-locking because it is reduced by the self phase modulation occurring in the long cavity.

In situ growth of optically active erbium doped Al2O3 thin films by pulsed laser deposition

Abstract: Thin Al2O3 films are grown and in situ doped with erbium by pulsed laser deposition in a single step process, by alternate ablation from Al2O3 and Er targets. The as‐deposited films have an Er step dopant profile throughout the film thickness, whose concentration depends on the number of pulses at the Er target. The as‐grown films are optically active, as evidenced by the photoluminescence spectrum centered at 1.533 μm, corresponding to intra‐4f transitions in Er3+. The photoluminescence intensity increases upon annealing due to an increase of the luminescence lifetime. This is most likely a result of a decrease in the nonradiative decay channels, related to annealing of defects in the Al2O3 film.

Investigation of diode-pumped 2.8-µm laser performance in Er:BaY2F8

Abstract: Laser operation at 2.8 mm in BaY2F8 with erbium concentrations of 7.5% and 20% is investigated under laser-diode pumping at 967 nm. Output powers as high as 250 mW and slope efficiencies as high as 24% are obtained. Results are comparable with those of Er3+:LiYF4 under the same pump conditions. Slope efficiencies above 30% are predicted for optimized erbium concentrations.

Planar waveguide and a process for its fabrication

Abstract: A planar waveguide and a process for making a planar waveguide is disclosed. The waveguide has a layer of doped host material formed on a substrate. The host material is a trivalent material such as a metal fluoride, wherein the metal is selected from the Group III B metals and the lanthanide series rare earth metals of the Mendeleevian Periodic Table. The dopant is a rare earth metal such as erbium. The waveguide has an emission spectrum with a bandwidth of about 60 nm for amplification of an optical signal at a wavelength of about 1.51 μm to about 1.57 μm. The waveguide is made by forming the layer of doped host material on a substrate. The film is formed by evaporating materials from two separate sources, one source for the dopant material and a separate source for the host material and forming a film of the evaporated materials on a substrate.

Pump-induced refractive index modulation and dispersions in Er/sup 3+/-doped fibers

Abstract: A novel measurement system provides determination of pump induced phase shifts in erbium doped fibers with an accuracy of /spl sim//spl pi//20 Using this system, a systematical analysis of the pump induced modulation of the refractive index and dispersions for a signal at 1550 nm and a pump at 980 nm is reported The analysis contains measurements of pump induced refractive index changes as function of wavelength, pump power, and doping concentration A model taking account of the contribution to the refractive index changes from optical transitions between /sup 4/I/sub 15/2/ states and /sup 4/I/sub 13/2/ states in Er/sup 3+/ yields good agreement to experimental results apart from a wavelength independent offset The offset is interpreted to originate from high energetic optical transitions The results show that for a large refractive index modulation, a short and highly doped fiber should be used with limited amplified spontaneous emission effect In optical communication systems comprising erbium doped fiber amplifiers, a tradeoff between dispersion and amplification must be made

Clustering effects on double energy transfer in heavily ytterbium–erbium-codoped silica fibers

Abstract: We study clustering effects in heavily ytterbium–erbium-codoped silica fibers. We demonstrate that the fraction of both ions found in clusters can exceed 50% in such fibers. A clustering effect is at the origin of an efficient double energy transfer process that generates a green fluorescence. An original method, based on a dynamic analysis of the ytterbium–erbium system, permits determination of the intracluster transfer rates involved, which are found to be high enough to compensate for the weak metastability of the erbium intermediate level.

Sol-gel synthesis of rare-earth-doped fluoride glass thin films

Abstract: This paper describes ZBLA fluoride glass thin films produced via an inexpensive, low-temperature reactive atmosphere sol-gel approach. Luminescence from erbium at 1.55 μm has been observed in x-ray-amorphous doped films deposited on calcium fluoride, polyimide, sapphire, and silicon substrates. Fluorescence studies of the erbium 4S3/2 → 4I13/2 transition, a characteristic emission for a reduced phonon energy host, were conducted for both sol-gel-derived films and conventionally prepared glass rods. The peak intensity observed from the sol-gel films was blue-shifted by 16 nm with a FWHM value approximately half that measured for the melt-quenched rods. Excitation studies indicate that, unlike conventionally prepared glasses, sol-gel materials suffer from nonradiative relaxation of the 4S3/2 excited state to the 4I9/2 level, where subsequent radiative emission to the 4I15/2 ground state occurs. The proposed source of the quenching mechanism are remnant species inherent to the sol-gel process. While this causes the luminescence behavior of rare-earth-doped sol-gel-derived fluoride materials to be similar to oxide hosts, these remnant species modify the branching ratios, resultantly leading to a novel 824 nm emission when excited at 488 nm.

Room temperature spectral hole-burning in erbium-doped fiber amplifiers

Abstract: Summary form only given. In this paper we report the first room temperature measurements of spectral hole-burning depths and widths of an Er-doped fiber amplifier (EDFA). The alumino-germano-silicate EDFA was pumped at 1480 nm and had a small signal gain of 25 dB at 1551 nm. Spectral gain measurements were carried out in the range 1535-1570 nm using a lock-in technique and spectral subtraction for accurate determination of SHB properties.

Stable and broadband Er-doped superfluorescent fibre sources using double-pass backward configuration

Abstract: Er-doped superfluorescent fibre sources (SFSs) pumped near 980 nm in double-pass backward configuration are characterised experimentally for the first time. By properly adjusting erbium doped fibre lengths, SFSs can have pump-power insensitive mean wavelength operations with broader linewidths and better pump efficiencies than those in the commonly adopted single-pass backward configuration.