Planar Optical Amplifiers Research Articles

Theoretical performance of a 1.5-µm satellite-borne coherent Doppler wind lidar using a planar waveguide optical amplifier with a demonstrated figure of merit: simulation of signal detection probability, measurement precision, and bias.

We report performance of a satellite-borne coherent Doppler wind lidar (SCDWL), which equips a planer waveguide amplifier (PWA) operating in a wavelength of 1.5 µm. The performance is defined by detection probability, measurement precision, and bias, and is characterized with a Doppler wind lidar (DWL) simulation that considers a realistic wind velocity profile, and instrumental and atmospheric parameters. Among the parameters, we carefully model those related to the PWA whose figure of merit has great impact on the performance of SCDWL and has shown rapid improvement in recent years. Moreover, we introduce three models for a backscattering coefficient (high, moderate, and low) to assess the influence from variation of atmospheric backscattering. Our simulation demonstrates that the SCDWL can work with reasonable performance for the target altitude of 6 km in the case of the high-backscattering model. The simulation also exhibits that the SCDWL can observe wind velocity at the altitude of 12 km if improved instrumental parameters or higher backscattering coefficients are considered. In addition, we reveal that non-uniform wind velocity distribution degrades the performance of the SCDWL and induces a bias between measured and real wind velocity.

Erbium–bismuth-doped germanium silicate active optic glass for broad-band optical amplification

This work deals with research and optimization of the optical Ge–Si glass composition doped with Er3+, Yb3+ ions and bismuth optically active centers (BACs), which are optically active for implementation in a double C- and U-band planar optical amplifier. The intention was to increase the range of amplified wavelengths in the NIR band up to 1650 nm. Various types of glass with different content of GeO2, SiO2 and Er2O3, Yb2O3 ions Bi2O3 were prepared and the luminescence response in the 1500–1700 nm range was tested. The maxima of the luminescence intensity in the optical bands and the spectral full width at half maximum (FWHM) were determined by modified reflex spectrum method measurement. The prepared Ge–Si glass doped with Er3+ ions and BACs exhibited strong and balanced emission in the 1520–1680 nm range after pumping at 1480 nm. The specific balanced differential gain of up to 0.2 dB/cm in the C-band and simultaneously 0.2 dB/cm in the U-band was measured. Our results proved that the luminescence of BACs depends on the presence of optical active Er3+ ions and germanium in matrix of glass, pumped by radiation 1480 nm and energy transfer from erbium to BACs have been newly observed in the Ge–Si glass. It has also been found that high content of germanium, comparable with silicon content is required for this transfer. The results show that the germano-silicate glass doped with Er3+ and Bi ions is a perspective material for the fabrication of broad-band amplifiers in the C- and U-bands.

Preparation and Physical Properties of Erbium-Doped Polymer Patterns by Micromolding in Capillaries for Optical Waveguide Amplifiers

Er3+-doped precursor solutions were first prepared using 2,2,3,3,4,4,5,5-octafluoropentyl acrylate as a fluoromonomer, tetrahydrofurfuryl acrylate as a solubility enhancer, Ebecryl 220 as a cross-linking agent, Darocur 4265 as a radical photoinitiator and erbium(III) trifluoromethane sulfonate as an erbium source with various weight ratios. The crosslinked, patterned and erbium-doped fluoropolymer films were fabricated by micromolding in capillaries on glass substrates for planar optical amplifier applications. The fluoropolymer films acting as host materials for the Er3+ ions had excellent transmission properties (more than 90% over the visible and near-infrared regions), high thermal decomposition temperatures (greater than 300°C) and the ability to support high erbium complex concentrations (up to 10 wt% based on the polymer matrix). These results are sufficient for the films to be used in planar optical amplifier applications.

Fabrication and Characterization of Erbium-Doped Fluoropolymer Patterns via UV-Nanoimprint Lithography for Use in Planar Optical Amplifiers

The Er-doped precursor solutions were first prepared using 2,2,3,3,4,4,5,5-octafluoropentyl acrylate as a fluoromonomer, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol diacrylate as a cross-linking agent, poly(2,2,3,3,4,4,4-heptafluorobutyl acrylate) as a binding polymer, Darocure 4265 as radical photoinitiator and erbium(III) trifluoromethane sulfonate as an erbium source with various weight ratios. The crosslinked, patterned and erbium-doped fluoropolymer films were fabricated by UV-nanoimprint lithography on glass substrates for application as planar optical amplifiers. The fluoropolymer films acting as a host material for the Er ions showed excellent transmission properties—more than 80% over the visible and near-infrared regions—a high thermal decomposition temperature greater than 350°C and the ability to support a high Er concentration—up to 10 wt% based on the polymer matrix. These results were good enough for the films to be used in planar optical amplifier applications.

Fabrication and Characterization of Erbium-Doped Polymer Patterns by Lift-Off Process for Planar Optical Amplifiers

Erbium-doped aqueous polymer solutions were prepared using polyvinylpyrrolidone as a host polymer, potassium persulfate as a thermal cross-linking agent, erbium (III) trifluoromethane sulfonate as an erbium source, ethylene glycol as an antifoaming agent and DISPERBYK-180 as a dispersing agent with various weight ratios. The cross-linked, patterned and Er3+-doped polymer films were fabricated using the solutions by a lift-off process for application to planar optical amplifiers. The polymer films fabricated in this study showed excellent transmission of more than 90% over the visible and NIR regions, a high thermal decomposition temperature of about 380°C and high Er3+ concentration up to 20 wt.% based on a polymer matrix without aggregation, making this material sufficient for planar optical amplifiers.

Integrated Al$_2$O$_3$:Er$^{3+}$ Zero-Loss Optical Amplifier and Power Splitter With 40-nm Bandwidth

A combined planar lossless optical amplifier and 1 × 2 power splitter device has been realized in Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> :Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> on silicon. Net internal gain was measured over a wavelength range of 40 nm across the complete telecom C-band (1525-1565 nm). Calculations predict net gain in a combined amplifier and 1 × 4 power splitter device over the same wavelength range for a total injected pump power as low as 30 mW.

Near-infrared luminescent properties and natural lifetime calculation of a novel Er3+ complex

in this communication, a novel Er3+ complex Er(PT)(3)TPPO [PT = 1-phenyl-3-methyl-4-tert-butylbenzoyl-5-pyrazolone, TPPO = triphenyl phosphine oxide] is successfully synthesized and characterized by elemental analysis and single-crystal X-ray diffraction. Its optical properties and the energy transfer process from the ligand PT to the Er3+ ion are investigated, the typical near-infrared (NIR) luminescence (centered at around 1530 nm) is attributed to the I-4(13/2) -> I-4(15/2) transition of Er3+ ion which results from the efficient energy transfer from PT to Er3+ ion (an antenna effect). The wider full width at half maximum (78 nm) peaked at 1530 nm in the emission spectrum and the Judd-Ofelt theory calculation on the radiative properties suggest that Er(PT)(3)TPPO should be a promising candidate for tunable lasers and planar optical amplifiers.

Solution-processable erbium–ytterbium complex for potential planar optical amplifier application

Novel erbium and erbium–ytterbium complexes based on 4-pentylbenzoate (PBa) groups and 1,10-phenanthroline (Phen) ligands have been synthesized and structurally characterized. The X-ray single crystal structure of the erbium–ytterbium complex indicates that it is a binuclear complex model with a short metal-to-metal distance (4.269 A), which facilitates the intramolecular Yb–Er energy-transfer process in the erbium–ytterbium complex. The optical properties for solid state films of the erbium–ytterbium complex prepared by spin-coating technique were studied in detail. The NIR PL spectrum of the film shows considerable room temperature emission at 1.53 µm with a large bandwidth (full width at half maximum) of 72 nm. The planar waveguide of the complex is capable of guiding 1550 nm light with low loss. The mechanism for the formation of high-quality films is also proposed according to the structural investigation. Our results show that the erbium–ytterbium complex film has promising potential for the planar optical amplifier application.

Si nanocluster sensitization of Er-doped silica for optical amplet using top-pumping visible LEDs

A review is presented of Si nanocluster sensitization of Er-doped silica for planar optical amplifiers using top-pumping 470-nm light-emitting diodes (LEDs). The motivation and basic physical principles underlying the nanocluster sensitization are first reviewed. The material structures necessary for optimum performances are presented, with emphasis on the need for nanoscale engineering of the composition and structure. Evidence of optical gain using commercial GaN-visible LEDs are presented, and the simulation results of possible device performances described. Finally, some possible future directions for research are discussed.

Stable heterometallic fluorinated β-diketonato/alkoxo complexes as precursors for Er-doped luminescence materials

New series of novel heterometallic fluorinated β-diketonato/alkoxo complexes have been synthesized in quantitative yields and characterized by analytical data, FT-IR, NMR and mass spectroscopy. Their thermal behavior was investigated by TGA. The plausible structure of β-diketonato/alkoxo complexes was suggested from the physico-chemical analysis. These complexes have been studied as potential precursors for planar optical amplifiers through the investigation of optical properties and a homogenous thin film spin coating. The volatility of these complexes was reduced by intramolecular hydrogen bonding. The assembling of fluorinated β-diketonato/alkoxo ligands ensures high coordination numbers for coordinated metals and improves their stability in ambient atmosphere.

Evidence of energy transfer from Si agglomerates to Er ions in aluminosilicate glass thin layers

This paper shows evidence of the possible excitation of Er ions in Si-rich aluminosilicate glass layers deposited by magnetron sputtering through an energy transfer from Si nanoagglomerates formed after annealing at 450 °C. The intensity of the Er emission was found unaffected by the change of the excitation line from resonant to nonresonant over a certain range of wavelengths. The time decay dynamics have been also determined using the 476.5-nm-off-resonant excitation. The lifetime values were found to range between 2 and 4.1 ms, while the effective excitation cross section reaches ∼4×10−6cm2, nearly 4 orders of magnitude higher than its counterpart for the direct excitation of Er3+ ions. These results enhance the potential use of aluminosilicate glasses for the fabrication of planar optical amplifiers.

A New Sol-Gel Material Doped with an Erbium Complex and Its Potential Optical-Amplification Application

The crystal structure of a ternary Er(DBM) 3 phen complex (DBM=dibenzoylmethane; phen=1,10-phenanthroline) and its in-situ synthesis via a sol-gel process are reported. The infrared (IR), diffuse reflectance (DR), and fluorescence spectra of the pure complex and the Er 3 + /DBM/phen co-doped luminescent hybrid gel, formed via an in-situ method (ErDP gel), have been investigated. The results reveal that the erbium complex is successfully synthesized in situ in the ErDP gel. Excitation at the maximum absorption wavelength of the ligands resulted in the typical near-IR luminescence (centered at around 1.54 μm) resulting from the 4 I 1 3 / 2 → 4 I 1 5 / 2 transition of the Er 3 + ion, which contributes to the efficient energy transfer from the ligands to the Er 3 + ion in both the Er(DBM) 3 phen complex and the ErDP gel (an antenna effect). The full width at half maximum (FWHM) centered at 1541 nm in the emission spectrum of the ErDP gel is 72 nm, which has potential for optical-amplification applications. Further theoretical analysis on the Er 3 + ion in the ErDP gel shows that it appears to be a promising candidate for tunable lasers and planar optical amplifiers.

Stimulated emission and optical gain in LaF3:Nd nanoparticle-doped polymer-based waveguides

We report experiments which show evidence that stimulated emission at 863nm takes place in hybrid monomode Si3N4 waveguides where LaF3:Nd nanoparticle-doped polymethylmethacrylate (PMMA) was used as a top cladding material. Furthermore, optical gain at 1319nm in LaF3:Nd nanoparticle dispersed PMMA (0.1dB∕cm) and photodefinable epoxy (Microchem SU-8) multimode waveguides has been observed at pump powers below 10mW. This class of composite materials based on polymers with dispersed nanoparticles shows promising properties for planar optical amplifiers. Simulation showed that optical gain in the order of 10dB can be achieved at 100mW pump power in a 20cm long monomode waveguide.

Study of the energy transfer mechanism in different glasses co-doped with Si nanoaggregates and Er3+ ions

Abstract In the past few years the incorporation of Si nanocrystals in Er doped silica was found to strongly enhance the infrared luminescence of Er 3+ at 1.54 μm as a consequence of an energy transfer process. This has important implications in the optoelectronic field, in particular for the realization of planar waveguide optical amplifiers. To this respect, multi-component glasses can offer better performances than silica in terms of Er solubility and band broadness. In this work we investigate the energy transfer mechanism in different glass hosts: common silica (S), aluminosilicate (L) glass and soda-lime (H) glass. Si and Er have been co-implanted in the substrates and post implantation thermal treatments have been performed to promote Si aggregation. The most intense Er 3+ PL emission at 1.54 μm was achieved after a thermal treatment at 400 °C for the L substrate and at 600 °C for the H substrate. Such emission was investigated in a wide range of excitation wavelengths (300–800 nm), showing a very efficient energy transfer process for all of the substrates. These results together with structural investigation allowed to evidence that the same kind of mechanism occurs in the different hosts. Our results based on Energy Filtered TEM suggest that good energy transfer mediators are small Si aggregates and not necessarily crystalline clusters.

Folded-Spiral EDWAs With Continuously Varying Curvature

The layout of folded spiral erbium-doped planar waveguide optical amplifiers (EDWAs) is considered. A quasi-continuous function to describe the curvature of a folded-spiral layout is presented, based upon the use of cosine and raised-cosine variations in bend curvature. This layout provides greater gain in a given area than the corresponding fixed-radii layout. Analysis is initially based on simple geometric principles and the reduction of bending losses for 180/spl deg/ waveguide bends. Fold-back bends and complete EDWA layouts are then considered. Simulations are carried out using an algorithm that combines five-level rate equations with propagation by the method of lines.

Enhanced Luminescence of an Erbium (III) Ion-Association Ternary Complex with a Near-Infrared Dye

A near-infrared (NIR) luminescent erbium (III) ternary complex has been prepared with an ion-associating sensitizer of IR5, a NIR dye whose large absorption cross section covers the visible spectrum around 488 nm and especially the NIR spectrum around 980 nm. In this paper NIR photoluminescence from the complex in bulky powder is obtained. The 1.54 μm emission of erbium ion upon 980 nm laser diode (LD) excitation is remarkably enhanced, as a result of effective indirect excitation of erbium ion via IR5 (harvesting most excitation light). The luminescence mechanisms upon indirect excitation are simply described. It is suggested that the investigated complex is potentially an active substance for the fabrication of planar optical amplifiers operating at 1.5 μm, which in particular can be conveniently based on cheap pumping sources such as 980 nm LDs and are compatible with the current optical communication network.

Broadband sensitizers for erbium-doped planar optical amplifiers: review

Three different broadband sensitization concepts for optically active erbium ions are reviewed: 1) silicon nanocrystals, with absorption over the full visible spectrum, efficiently couple their excitonic energy to Er3+, 2) silver-related defect states in sodalime silicate glass have absorption in the blue and transfer energy to Er3+, and 3) organic cage complexes coordinated with well-chosen chromophores serve as broadband sensitizers in the visible. Energy transfer rates, efficiencies, and limiting factors are addressed for each of these sensitizers. Implications of the use of strong sensitizers for planar waveguide design are illustrated by using a model for the sensitizing effect of ytterbium.

Bit-rate and format conversion from 10-Gbit/s WDM channels to a 40-Gbit/s channel using a monolithic Sagnac interferometer integrated with parallel-amplifier structure

Full bit-rate conversion from 10-Gbit/s random wavelength-division multiplexing (WDM) channels to a 40-Gbit/s channel, including non-return-to-zero (NRZ) to return-to-zero (RZ) format conversion and reconversion, was successfully demonstrated. The key technique is wavelength conversion using a monolithic Sagnac interferometer integrated with a parallel-amplifier structure. Good eye-openings through the 10-Gbit/s NRZ to 40-Gbit/s RZ, and 40-Gbit/s RZ to 10-Gbit/s NRZ conversions were obtained. Error-free operation and a small power penalty of less than 0.8 dB were achieved. Phase adjustment of 10 Gbit/s signals was also successfully demonstrated with slight wavelength conversions using a planar lightwave circuit and semiconductor optical amplifier hybrid integrated Mach–Zehnder inteferometer.

Fluoride glass planar waveguides for active applications

To help develop an efficient planar optical amplifier, the single mode behaviour of large cross-section rib optical waveguide structures (15 μm high and up to 19 μm wide) made of fluoride glasses have been investigated numerically. Wet chemical etching offers a simple and cheap solution for the fabrication of rib patterns in fluoride glasses, we present measurement of the lateral rib roughness left by this process as well as calculation of consequent scattering losses. We show that such large cross-section rib waveguides show a better tolerance to the rib roughness than standard semiconductor waveguides. This is of practical importance in order to make use of the full benefit of the amplification.

Fiber-device-fiber gain from a sol-gel erbium-doped waveguide amplifier

An erbium-doped silica-on-silicon planar waveguide optical amplifier is described. The active core is a topographic guide formed from aluminophosphosilicate glass doped with erbium and ytterbium. The buffer is formed from silica deposited by thermal oxidation and the cladding from borophosphosilicate glass obtained by plasma-enhanced chemical vapor deposition. The use of low process temperatures allows relatively heavy doping and careful control of the core etching allows low background insertion losses to be obtained. Spontaneous emission and gain measurements are given and 5.4-dB fiber-device-fiber gain is demonstrated using a 5-cm-long chip pumped using a 980-nm laser diode at 175-mW pump power.