Er-doped Waveguide Research Articles

Absorption cross section and signal enhancement in Er-doped Si nanocluster rib-loaded waveguides

Pump and probe experiments on Er3+ ions coupled to Si nanoclusters have been performed in rib-loaded waveguides to investigate optical amplification at 1.5μm. Rib-loaded waveguides were obtained by photolithographic and reactive ion etching of Er-doped silica layers containing Si nanoclusters grown by reactive sputtering. Insertion losses measurements in the infrared erbium absorption region allowed to gauge an Er3+ absorption cross section of about 5×10−21cm2 at 1534nm. Signal transmission under optical pumping at 1310nm shows confined carrier absorption of the Si nanoclusters. Amplification experiments at 1535nm evidence two pump power regimes: Losses due to confined carrier absorption in the Si nanoclusters at low pump powers and signal enhancement at high pump powers. For strong optical pumping, signal enhancement of about 1.2dB∕cm was obtained.

Improvement of the Optical Gain in the Er-Doped Lithium Niobate Waveguide Optical Amplifiers

This paper describes improvement of the gain in the Er-doped lithium niobate waveguide optical amplifiers. A new configuration is proposed, which is loaded with a high-index cladding for the purpose of realizing a larger overlap between the guided light fields and doped Er ion-concentration. It is shown by theoretical simulations and also by experiments that the clad is advantageous to shifts of the light fields toward the substrate surface, and that the overlap between the light field and Er ion-concentration becomes large. Improved optical gains are measured for a fabricated device with a thin-TiO 2 clad in the LiNbO 3 substrate.

Automatic feedback control of an Er-doped fiber laser with an intracavity loss modulator

Suppression of Q-switching instabilities with an actively controlled intracavity loss modulator is demonstrated in an Er-doped waveguide laser that is mode locked with a slow saturable absorber at repetition rates of as much as 100 MHz. By automatic gain control in the feedback loop, stable mode locking is achieved over the entire parameter range of the laser. This approach renders laser stabilization independent of the characteristics of the gain medium and intracavity power. The pulse-shaping dynamics is not affected by the presence of the intracavity loss modulator.

Gain characteristics of 6 cm-long Er-doped bismuthate waveguide

Er-doped muliticomponent bismuthate channel waveguides have been fabricated. Dependence of emission lifetime of Er3+ ions on the concentration of Er3+ ions is investigated and compared with the other silicate materials. The loss and gain characteristics of the channel waveguide are reported.

Optical gain at 1.5 /spl mu/m in nanocrystal Si-sensitized Er-doped silica waveguide using top-pumping 470 nm LEDs

This paper demonstrates optical gain at 1.5 /spl mu/m in Si-nanocrystal-sensitized, Er-doped silica waveguide using a commercial, low-cost 470 nm LED in top-pumping configuration. Experimental evidence of full inversion with maximum possible gain of 3 dB/cm is presented. Possible application of Si-nanocrystal-sensitized, Er-doped silica for silicon-based microphotonics is also presented.

Performance analysis of nanocluster-Si sensitized Er-doped waveguide amplifier using top-pumped 470nm LED

We analyze the performance of nanocrystal-Si (nc-Si) sensitized Er-doped waveguide amplifier using coupled nc-Si-Erbium rate equation, and suggest novel structures / operation methods which can be used to enhance its performance figures. With 2-dimensional modified propagation equation applied for the pump / signal waves along with modest assumptions on design parameters, we show that 10dB of gain with 0dBm input signal can be achieved with currently available pump LED power.

Compositional Profiles in Silica-Based Sol-Gel Films Doped with Erbium and Silver, by RBS and ERDA

The photoluminescence efficiency of Er-doped silica-titania planar waveguides, prepared by sol-gel processing, may in principle be enhanced through the incorporation of silver metal particles. On the other hand, the presence of residual OH groups limits the optical activity of the Er3+ ions. In this work, we have used Rutherford Backscattering Spectrometry (RBS), combined with Elastic Recoil Detection Analysis (ERDA), in order to study the incorporation of Ag and H species as a function of the heat treatments used to densify the sol-gel films. Ultraviolet–visible spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to support and expand the interpretation of the RBS and ERDA data. The RBS results indicate a homogeneous distribution of Er in the as-deposited films. On the contrary, Ag displays a bimodal in-depth profile, centred at the air/film and film/Si substrate interfaces. Heat treatments at up to 700°C eventually lead to in-diffusion and segregation of most of the Ag species at the latter interface. The hydrogen concentration reaches minimum values after heat treatments at 500 and 900°C, with apparently larger values for temperatures in between. During these heat treatments, the Er profile remains stable.

Pump-probe experiments on Er coupled Si-nanocrystals rib-loaded waveguides

ABSTRACTPump and probe experiments have been performed on Er-doped rib-loaded waveguides containing Si nanoclusters grown by reactive magnetron sputtering. An Er3+ absorption cross-section of about 5×10−21 cm2 has been found at 1534 nm by insertion losses measurements. Transmission measurements at 1310 nm under optical pumping (488 nm) shows a decreasing of the signal because of confined carrier absorption of the Si nanoclusters. Amplification experiments at 1535 nm evidence two pump power regimes: losses due to confined carrier absorption in the Si nanoclusters at low pump powers and signal amplification at high pump powers. For strong optical pumping, signal enhancement of about 1.2 dB/cm was observed.

A High Index Contrast Silicon Oxynitride Materials Platform for Er-doped Microphotonic Amplifiers

AbstractEr-based optical amplification continues to be the ideal low noise, WDM crosstalk free, broadband candidate for waveguide amplifiers. Design analysis of the applicability of Er-Doped Waveguide Amplifiers (EDWAs) for micron-scale integrated photonics in a planar lightwave circuit concludes: (i) an >80× increase in gain efficiency, and (ii) a >40×increase in device shrink can be realized, for a high index contrast EDWA (with a core-cladding index difference of δn=0.1↔0.7), compared to a conventional Er-doped fiber amplifier. The materials challenge now is to establish a robust materials system which meets this high index difference design requirement while simultaneously leveraging the capability of silicon (Si) processing: a host platform for EDWAs must be found which can integrate with Si Microphotonics. Silicon nitride (Si3N4), silicon oxide (SiO2) and a miscible silicon oxynitride alloy (SiON) of the two meet this materials challenge. We present the results of reactive and conventional magnetron sputtering based materials characterization for this high index host system. Room temperature and 4 K photo-luminescence studies for annealed samples show the reduction of non-radiative de-excitation centers while maintaining an amorphous host structure. Atomic force microscopy shows less than 1 nm peak-to-peak roughness in deposited films. Prism coupler measurements show a reliable reproducibility of host index of refraction with waveguide scattering loss <2 dB/cm. We conclude that the SiON host system forms an optimal waveguide core for an SiO2-clad EDWA. Initial gain measurements show a gain coefficient of approximately 3.9 dB/cm.

Index contrast scaling for optical amplifiers

A scaling methodology for optically pumped waveguide amplifiers is presented as a function of their core-cladding index contrast. Increasing index contrast results in two crucial advantages: 1) an increase in gain efficiency and 2) a decrease in the areal footprint of a planar structure. Increasing index contrast is observed to have no effect on the output noise figure. A figure of merit summarizing these advantages demonstrates the powerful role of index contrast as an enabler for improving planar amplifier performance. Design rules are presented in the form of performance maps, allowing waveguide designers to optimize amplifier length and footprint. Using the Er-doped waveguide amplifier as a case study, we design an optical amplifier with >3-dB/cm gain within a 300/spl times/300-/spl mu/m/sup 2/ area, powered by a single 1-mW pump source. This work represents a design rule approach for making a scalable microphotonic optical amplifier.

Coefficient determination related to optical gain in erbium-doped silicon-rich silicon oxide waveguide amplifier

Gain-determining coefficients in Er-doped, nanocrystal-Si (nc-Si) sensitized silica waveguide amplifiers are investigated. Single-mode, Er-doped silica waveguides with nc-Si embedded in them were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition of Er-doped a-Si:Ox (x<2) followed by a high-temperature anneal to precipitate nc-Si. Exciting the Er ions via nc-Si by pumping the waveguide from the top with the 477 nm line of an Ar laser resulted in an enhancement of the transmitted 1535 nm signal of up to 14 dB/cm, indicating a possible net gain of up to 7 dB/cm. From the dependence of the signal enhancement upon the pump power, an emission cross section of 2×10−19 cm2 at 1535 nm and an effective excitation cross section of ⩾10−17 cm2 at 477 nm is obtained.

Fabrication and Characterization of Er-Diffused Ti:LiNbO3 Waveguide Lasers

Er-doped LiNbO3 waveguide lasers are attractive for implementation of waveguide devices with novel functions, although the fabrication techniques are not fully-established yet. Fabrication and characterization of an Er-diffused Ti:LiNbO3 waveguide lasers are demonstrated in this paper. Thermal diffusion technique was used for Er-doping into z-cut LiNbO3. A Fabry-Perot type laser cavity consisting of a Ti:LiNbO3 channel waveguide, a dichroic and an Al mirrors was fabricated on the crystal. The Al mirror allowed double-pass pumping. The device was optically pumped at 1.48 µm wavelength using a laser diode, and a continuous wave (CW) laser oscillation was achieved at 1.53 µm. The threshold was 74 mW, and an output power of ∼ 1 mW was obtained. The results agreed with theoretical prediction fairly well. The device design was studied theoretically for higher performance.

Er-doped silica-based waveguides prepared by différent techniques: RF-sputtering, sol-gel and ion-exchange

Erbium-activated silica-based planar waveguides were prepared by three different technological routes: RF-sputtering, sol–gel and ion exchange. Various parameters of preparation were varied in order to optimize the waveguides for operation in the NIR region. Particular attention was devoted to the minimization of the losses and the increase of the luminescence efficiency of the metastable 4I13/2 state of the Er3+ ion. Waveguide properties were determined by m-line spectroscopy and loss measurements. Waveguide Raman and luminescence spectroscopy were used to obtain information about the structure of␣the prepared films and about the dynamical processes related to the luminescence of the Er3+ ions.

A numerical analysis of gain characteristics of Er-doped Al2O3 waveguide amplifiers

The gain characteristics of erbium-doped Al2O3 waveguide amplifiers are investigated by solving numerically rate equations with upconversion effects and propagation equations. We obtained the dependence of gain of erbium-doped Al2O3 waveguide amplifiers on the waveguide length, erbium concentration and pump power at different pumping wavelengths (980 and 1480 nm). The performance of amplifiers pumping at 1480 and 980 nm are compared. It is shown that 980 nm pumping has higher gain and higher pumping efficiency. The parameters of waveguide amplifiers have been optimized. A optical gain of 43 dB can be achieved for a optimum waveguide length of 8.25 cm and 5.8 × 1020 cm−3 Er concentration pumped with 100 mW at 980 nm, that is a gain of 5.2 dB/cm.

Gain limiting processes in Er-doped Si nanocrystal waveguides in SiO2

Erbium-doped Si nanocrystal based optical waveguides were formed by Er and Si ion implantation into SiO2. Optical images of the waveguide output facet show a single, well-confined optical mode. Transmission measurements reveal a clear Er related absorption of 2.7 dB/cm at 1.532 μm, corresponding to a cross section of 8×10−20 cm2. The Si nanocrystals act as sensitizers for Er but under high doping conditions (∼50 Er ions per nanocrystals) no pump-induced change in the Er related absorption is observed under optical pumping (λ=458 nm), which is ascribed to an Auger quenching effect. For very high pump powers, a broad absorption feature is observed, attributed to free carrier absorption.

Spectroscopic investigation of proton exchanged Er-doped LiNbO3 waveguides

In this work, the spectroscopic properties of locally Er3+ -doped LiNbO3 waveguides obtained by proton exchange (PE) and reverse proton exchange (RPE) techniques have been explored. It has been found that the presence of protons induces an increment in the non-radiative de-excitation probabilities which affects the dominant emission bands of the Er3+ ions as well as their temporal evolution.

Exciton–erbium energy transfer in Si nanocrystal-doped SiO 2

Silicon nanocrystals were formed in SiO 2 using Si ion implantation followed by thermal annealing. The nanocrystal-doped SiO 2 layer was implanted with Er to peak concentrations ranging from 0.015 to 1.8 at.%. Upon 458 nm excitation, a broad nanocrystal-related luminescence spectrum centered around 750 nm and two sharp Er luminescence lines at 982 and 1536 nm are observed. By measuring the temperature-dependent intensities and luminescence dynamics at a fixed Er concentration, and by measuring the Er concentration dependence of the nanocrystal and Er photoluminescence intensity, the nanocrystal excitation rate, the Er excitation and decay rate, and the Er saturation with pump power we conclude that: (1) the Er is excited by excitons recombining within Si nanocrystals through a strong coupling mechanism; (2) the exciton–Er energy transfer rate is >10 6 s −1; (3) the exciton–Er energy transfer efficiency is >60 %; (4) each nanocrystal can have at most ∼1–2 excited Er ions in its vicinity, which is attributed to either an Auger de-excitation or a pair-induced quenching mechanism; (5) at a typical nanocrystal concentration of 10 19 cm −3, the maximum optical gain at 1.54 μm of an Er-doped waveguide amplifier based on Si nanocrystal-doped SiO 2 is ∼0.6 dB cm −1; (6) the effective Er excitation cross-section using this nanocrystal sensitization scheme is σ eff≈10 −15 cm 2 at 458 nm, which is a factor 10 5–10 6 larger than the cross-section for direct optical pumping of Er. This enables the fabrication of an Er-doped nanocrystal waveguide amplifier that can be pumped using a white light source.

Erbium-Doped Barium Titanate Thin FilmWaveguides For Integrated Optical Amplifiers

AbstractThe factors affecting optical gain were studied for Er-doped BaTiO3 thin film waveguides. Er-doped BaTiO3 with dopant concentrations of 0.3 – 9 at.% was deposited by metal-organic chemical vapor deposition. The luminescence efficiency was maximized by optimizing the growth temperature and erbium concentration as well as by post-deposition annealing. Stimulated emission was studied using the pump-probe technique over the spectral range of 1,520-1,550 nm. A maximum differential gain of 3 dB/cm was measured at 1,540 nm in an 8 mm long, 8 μm wide ridge waveguide.

Erbium-Doped Barium Titanate Thin Film Waveguides For Integrated Optical Amplifiers

AbstractThe factors affecting optical gain were studied for Er-doped BaTiO3 thin film waveguides. Er-doped BaTiO3 with dopant concentrations of 0.3 – 9 at.% was deposited by metal-organic chemical vapor deposition. The luminescence efficiency was maximized by optimizing the growth temperatureand erbium concentration as well as by post-deposition annealing. Stimulated emission was studied using the pump-probe technique over the spectral range of 1,520-1,550 nm. A maximum differential gain of 3 dB/cm wasmeasured at 1,540 nm in an 8 mm long, 8 μm wide ridge waveguide.

Thermal evaporation of rare-earth chlorides: application to vapor phase deposition of rare earth-doped fluoride glass waveguides

A systematic study of the evaporation rate for single and binary mixtures of rare earth (RE) chlorides (NdCl 3,ErCl 3,TmCl 3,PrCl 3,YbCl 3) has been performed. Single RE chlorides follow the physical evaporation law except NdCl 3 that could be explained by a possible dimerisation in the vapor state. Erbium- and neodymium-doped planar and channel waveguides have been prepared by dual evaporation of RE chloride and PbF 2–ZnF 2–GaF 3 fluoride glass. Also, planar waveguides are attacked by atmospheric moisture whereas, channel waveguides are stable, suggesting that the deposited glass is more compact in the latter case. The low optical loss (0.4 dB/cm at 633 nm for 1.5 mol% Er-doped channel waveguide) outlines the good quality of these devices.