Active Planar Waveguides Research Articles

Synthesis and luminescence characteristics of yttrium, aluminum and lanthanum borates doped with europium ions (Eu 3+)

Inorganic materials doped with rare earth (RE) ions are an object of intense research due to their optical and electrical properties. These materials have the potential for various applications, such as solid-state lasers, active planar waveguides, optical fiber amplifiers, light-emitting diodes (LEDs), displays, ink fillers, security features, etc. RE trivalent ions can emit light from the ultraviolet (UV) to the near-infrared (NIR) regions due to electronic transitions of the 4f-5d levels. Yttrium borate doped with europium ions was prepared by solid-state synthesis in a muffle furnace at 900oC for 4 hours, while lanthanum and aluminum borates doped with europium ions were prepared at 1000oC for 6 hours again in a muffle furnace. The resulting materials are fine white powders. Among the rare earth ions, europium is one of the most commonly used activators because the ions of Eu3+ and Eu2+ can be used as emission sites in the host lattices. Eu3+ ions can produce effective sharp emission peaks in different matrix compositions. Photoluminescence analysis of the samples was performed, based on which the luminescence intensity of the Eu3+ ion was determined through a comparative characteristic. YBO3:Eu3+ phosphor is optically active and chemically stable. It is characterized by a strong orange-red emission at ≈ 591 nm, ≈ 612 and ≈ 696 nm due to the 5D0→7F1 and 5D0→7F2 electronic transitions, respectively. Red emission is also observed for LaBO3:Eu3+ at ≈ 592 and ≈ 615 nm, characterizing the 5D0→7F1 and 5D0→7Fj (j=0, 1, 2, 3, 4) transitions. While aluminum borate doped with europium ion shows intense emission at ≈ 612 nm, making this material suitable for lighting devices. The technique of Fourier transform infrared spectroscopy (FTIR) was used to study the structure of the obtained materials.

Low losses Er3+-doped flexible planar waveguide: Toward an all-glass flexible planar photonic system

Thin films have a crucial role in integrated optics. The development of passive and active devices such as splitters, waveguides, multiplexers and optical amplifiers is by now established on rigid substrates. Therefore, an important further step to improve this kind of technologies and open the route to new applications is to extend these functionalities to mechanically flexible devices. One fundamental brick to obtain this features extension is the fabrication of low loss inorganic active planar waveguides on flexible glass substrate. Here, we present the preliminary results of a novel top-down fabrication of an active SiO2–HfO2:Er3+ all-glass flexible planar waveguide, via radio frequency sputtering. The waveguiding system, deposited on ultrathin flexible glass substrate, showed an attenuation coefficient lower than 0.2 dB/cm at 1.53 μm and exhibits emission in the NIR region.

Super Broadband at Telecom Wavelengths From RE3+-Doped SiO2-Ta2O5 Glass Ceramics Planar Waveguides.

This paper reports on the preparation of Er3+/Yb3+/Tm3+, Er3+/Yb3+/Nd3+, and Er3+/Tm3+/Nd3+ triply doped and Er3+-doped SiO2-Ta2O5 glass ceramic nanocomposites and active planar waveguides by the sol–gel process using the dip-coating technique as deposition method. The investigation of their structural, morphological, and luminescent properties using XRD, AFM, and photoluminescence analysis, are reported here. The XRD results showed the presence of L-Ta2O5 nanocrystals dispersed in the SiO2-based amorphous host for all the nanocomposites and films. The rare earth ion (RE3+) doping concentration affected both the crystallinity, and the crystallite sizes of the Ta2O5 dispersed into SiO2-Ta2O5 nanocomposites and waveguides. AFM characterization revealed crack free and smooth surface roughness and differences in viscoelasticity on the Er3+-doped SiO2-Ta2O5 films surface, which allows the identification of Ta2O5 nanocrystals on the SiO2 amorphous host. The Er3+ doped and triply doped SiO2-Ta2O5 nanocomposites displayed broad- and super broadband NIR emissions with a FWHM up to 173 nm achieved in the telecom wavelengths. The lifetime of the 4I13/2 emitting level of the Er3+-doped SiO2-Ta2O5 waveguides is strongly dependent on Er3+ concentration and an emission quenching was negligible up to 0.81 mol%. The structural and luminescent investigations indicated that RE3+-doped SiO2-Ta2O5 glass ceramics are promising candidates for photonic applications in optical devices operating in wide wavelengths at the telecom bands.

Effect of Increasing Temperature on 1.5 μm Spectroscopic Emission of Er<sup>3+</sup> Ions Activated Phospho-silicate Thin Film

Different concentrations of Er³⁺ ions- embedded nano-composite phospho-silicate ranging from 1 up to 3.5 mol % in thin film, symbolic as (S20P), (S20P1Er)T, (S20P2.5Er)T and (S20P3.5Er)T, respectively were prepared as advanced materials for planar waveguide application. Spin coating sol gel technique will be used to prepare the thin films. The prepared thin films optical and spectroscopic assessments were performed using transmittance, absorption, Raman, photoluminescence and refractive index (n) calculations. The observed transmittance T (%) and reflectance R (%) spectra were measured using Jasco V-570 spectrophotometer, in wavelength range (0.2-2.5 µm), confirmed good transparency for the prepared films, where the T (%) was higher than 92% and S20P1ErT was the most transparent one. The mentioned higher transparency presence was considered as a big challenge, especially after doping the silica gel with such higher phosphorus molar percent up to 20 mol %. Such challenge confirmed that the prepared thin films were suitable for the low losses and active planar waveguide fabrication. The room temperature photoluminescence (RTPL) quenching was observed at lower temperature 100°C for (S20P3.5Er)T. Emission at 1.5 µm upon excitation at 514.5 nm was detected and characteristic to the ⁴I_13/2→⁴I_15/2 erbium ions intra-4F transition for all prepared samples. The morphology of the prepared thin films was examined by using the Field emission scanning electron microscope (FESEM), while the measured film thickness obtained from cross section view from the (FESEM) give rise to 1.791 µm value for (S20P3.5Er)T. The bigger moderate thickness than 1 µm was an adequate parameter for supporting planar optical wave guide applications.

Differential Gain Comparison of Optical Planar Amplifier on Silica Glasses Doped with Bi-Ge and Er, Yb Ions

The paper presents the measurement and calculation of the optical amplifier gain and the optimal length of the active optical amplifier waveguide doped with Bi-Ge radiation complexes compared to an optical amplifier with active doping with ions Er3+, Yb3+. At present are using optical amplifiers for the high-capacity optical communication systems in the narrow spectral region of 1530–1560 nm, determined by the gain bandwidth of erbium-doped fiber amplifiers (EDFA) or erbium-doped optical planar amplifiers (EDPA) realized as active planar waveguides in the optical integrated circuits technique. However, it is possible increase wavelength region up to 1610 nm, where optical losses of telecommunication fibers are less than 0.3 dB per km, if appropriate amplifiers are available. In this regard, the development of novel optical amplifiers operating in this spectral region have of great importance. The paper summarizes the results measurement of the attenuation and emission spectra for net gain spectra calculation of the new ion exchange Ag+ – Na+ optical Er3+ and Yb3+ doped active planar waveguides realized on silica glass substrates and parameters of novel optical amplifiers for extension of the bandwidth from 1530 to 1610 nm doped by bismuth – erbium ions.

Simple derivative-free method of zero extraction by phase-based enclosure for determination of complex propagation constants in planar multilayer waveguides.

A rigorous and simple way to implement a numerical method for extracting the propagation constants and modal characteristics of lossless, lossy, and active planar multilayer waveguides is presented. The method can accurately determine the complex propagation constants of both guided and leaky modes. The method does not utilize the derivative of the dispersion function nor any integrals of it. It is based on finding the estimates of the zeros of the dispersion function by a systematic successively tighter enclosure of the zeros with exclusive use of only the phase of the dispersion function along varying rectangular contours in the complex plane. The zero estimates are then refined by Müller's iterative scheme employing deflation. The method was named derivative-free zero extraction by phase-based enclosure (DFZEPE) for brevity. The DFZEPE method has been applied to lossless, lossy, active, and antiresonant reflecting optical waveguides published in the literature and analyzed with similar methods, and the results are excellent. The proposed DFZEPE method has global convergence and can be applied to a plethora of electromagnetic (and other) problems where the zeros of an analytic function are sought.

Effect of photonic stop-band on the modes of a weakly scattering DCM-PVA waveguide random laser

We present an experimental study on the effect of the photonic stop-band (PSB) on the random laser (RL) emission characteristics of a 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) doped polyvinyl alcohol (PVA) film (DCM-PVA). The film, having its refractive index greater than the substrate and density variations at the microscopic scale, acts as a disordered active planar waveguide. The propagation losses for the transverse magnetic (TM) and transverse electric (TE) modes of the waveguide are observed to be 0.50 and 0.74 dB/cm, respectively, at λ = 632.8 nm. The waveguiding DCM-PVA film is then sandwiched between two silica 3-D photonic crystals (opals). The overlap of the DCM-PVA photoluminescence with the PSB of the opals is controlled by the choice of the particle size used for opal fabrication. The random lasing threshold studies have been carried out for both TM and TE polarizations for opals with different particle sizes. A reduction in the threshold of RL emission, with respect to the DCM-PVA waveguide, by about 20 times (to 0.67 mJ/cm2) is observed when the photoluminescence of the DCM-PVA film overlaps with the PSB of the opal structure for TM polarization, showing that the embedding of an RL in an engineered PSB material is an effective way to reduce the thresholds of RLs.

Formation of channels containing lead sulfide quantum dots using continuous-wave laser for active planar waveguides in glasses

PbS quantum dots (QDs) and channels containing QDs were fabricated by irradiation with a continuous-wave (cw) laser at λ = 532 nm. Channels with diameters of 36 ~52 μm were formed by scanning with the laser at 6-8 μm•s−1. Photoluminescence centered at λ = 1290 nm was recorded. Precipitation of PbS QDs inside glasses increased their refractive indices by as much as ~0.002. These channels are expected to provide active waveguides that operate in telecommunication windows once the diameters of PbS QDs can be controlled precisely.

Low threshold simultaneous multi-wavelength amplified spontaneous emission modulated by the lithium fluoride/Ag layers.

This paper describes a multi-wavelength amplified spontaneous emission (ASE) with multilayer stacked active planar waveguides. A modulating layer of Ag is applied to make a good confinement of ASE in one active layer, while a lithium fluoride layer is inserted between the active layer and the modulating layer to avoid fluorescence quenching and confine the pump energy in one waveguide. Under optical pumping, ASE at 503 and 662 nm corresponding to the respective active layer are simultaneously observed, with extremely low thresholds at ~37.2 and ~39.7 KW/cm2.

Photoluminescence in oxidized nanoporous silicon doped with erbium ions

This paper presents the results of a study of the structural, optical, and photoluminescence properties of a thin layer of oxidized nanoporous silicon doped with erbium ions. Structural studies have shown that silicon nanoclusters of spherical shape with dimensions from 5 to 35 nm are present in the layer. The transmittance of a layer of oxidized nanoporous silicon doped with erbium ions in the wavelength region from 1.2 to 2.0 μm was at least 54%, and this makes it possible to use it to create active planar waveguides that can be used in integrated optical structures of silicon photonics. Investigation of the photoluminescence spectra at temperatures of 100 and 300 K showed the presence of peaks that characterize the luminescence of erbium ions.

Design and Analysis of High-Speed, High-Contrast All-Optical Modulator Based on CdSe Quantum Dot-Doped Glass

To elucidate the theoretical foundation of an all-optical modulator (AOM) based on semiconductor quantum dots (QDs), numerical analysis have been performed, which is supported by the rate equations. Coupled rate and propagation equations have been solved toward investigating the carrier dynamics and optical behavior of the introduced AOM. A modulation depth (MD) of ~96% has been achieved in the output probe signal at the telecommunication wavelength of 1522 nm through an active planar waveguide design on silicon platform with a length of 200 μm for a pump power density of 5.6 MW/m2 at the visible wavelength of 460 nm. Results indicate that the MD remains constant, until the pump frequency exceeds 71 GHz; the higher the pump frequency, the lower the MD. The throughput extinction ratio of the AOM is ~15 dB at the mentioned roll-off frequency. The MD decreases to ~45% while the modulation frequency reach to 1 THz. Also, the designed AOM based on cadmium selenide (CdSe) QDs operates with the switching energy of ~10 fJ.

Preparation and study of the titanium oxide thin films doped with Tb3+ and Ce3+ ions

In this study, we investigated the dependence of the thickness and refractive index of thin films on the withdrawal speed. The films were produced by dip-coating on a glass substrate. The hydrolytic (conventional) sol-gel method was used in the preparation of titanium alkoxide, which were obtained by homogenizing tetraethylorthotitanate stabilized by beta-diketone (2,4-pentanodione) in an alcohol solution. Potential applications, such as active planar waveguides, were evaluated by m-line spectroscopy, electron absorption spectra in the ultraviolet visible region, and photoluminescence. Based on the m-line measurements, the thickness of the films obtained from the homogenized sols were found to be dependent on the withdrawal speed. The thickness range from 400 to 500 nm to the films prepared by withdrawal speed 100 mm/min, 600 to 700nm using 200 mm/min, and 800 to 900 nm to withdrawal speed 300 mm/min. The refractive index is not affected by deposition speed. The photoluminescence of the Tb III ion exhibited lines that were attributed to the transitions characteristic of this ion, i.e., transitions from the 5D4 excited state to the 7FJ (J=3,4,5,6) fundamental state.

Photoluminescence waveguiding in CdSe and CdTe QDs–PMMA nanocompositefilms

In this paper, active planar waveguides based on the incorporation of CdSe and CdTenanocrystal quantum dots in a polymer matrix are demonstrated. In the case ofdoping the polymer with both types of quantum dots, the nanocomposite filmguides both emitted colors, green (550 nm, CdTe) and orange (600 nm, CdSe). Theoptical pumping laser can be coupled not only with a standard end-fire couplingsystem, but also directing the beam to the surface of the sample, indicating a goodabsorption cross-section and waveguide properties. To achieve these results, astudy of the nanocomposite optical properties as a function of the nanocrystalconcentration is presented and the optimum conditions are found for waveguiding.

Characterization of active waveguides fabricated by ultralow-fluence swift heavy ion irradiation in lithium niobate crystals

We report on the fabrication of neodymium-doped lithium niobate active planar waveguides based on the generation of non-overlapping nano-tracks by ultralow-fluence swift heavy ions. A combination of confocal luminescence, Raman and surface second harmonic investigations have evidenced the simultaneous presence of partial amorphization, damage and local compression of the lithium niobate network along the ion path, with these effects being at the basis of the refractive index modification. The potential application of the obtained waveguides in multi-functional laser devices has been discussed.

Sol-gel preparation of near-infrared broadband emitting Er 3+-doped SiO 2-Ta 2O 5 nanocomposite films

This article reports a study on the preparation, densification process, and structural and optical properties of SiO 2-Ta 2O 5 nanocomposite films obtained by the sol-gel process. The films were doped with Er 3+, and the Si:Ta molar ratio was 90:10. Values of refractive index, thickness and vibrational modes in terms of the number of layers and thermal annealing time are described for the films. The densification process is accompanied by OH group elimination, increase in the refractive index, and changes in film thickness. Full densification of the film is acquired after 90 min of annealing at 900 °C. The onset of crystallization and devitrification, with the growth of Ta 2O 5 nanocrystals occurs with film densification, evidenced by high-resolution transmission electron microscopy. The Er 3+-doped nanocomposite annealed at 900 °C consists of Ta 2O 5 nanoparticles, with sizes around 2 nm, dispersed in the SiO 2 amorphous phase. The main emission peak of the film is detected at around 1532 nm, which can be assigned to the 4I 13/2 → 4I 15/2 transition of the Er 3+ ions present in the nanocomposites. This band has a full width at half medium of 64 nm, and the lifetime measured for the 4I 13/2 levels is 5.4 ms, which is broader compared to those of other silicate systems. In conclusion, the films obtained in this work are excellent candidates for use as active planar waveguide.

Characterization of laser waveguides in Nd:CNGG crystals formed by low fluence carbon ion implantation

We report on Nd:CNGG active planar waveguides produced by 6.0 MeV carbon ion implantation at fluence from 1 × 10 14 ions/cm 2 to 8 × 10 14 ions/cm 2. The refractive index profiles, which were reconstructed according to the measured dark mode spectroscopy, showed that the refractive indices had negative changes in the surface region, forming typical barrier waveguide. The width of waveguide structure induced by carbon ion implantation is ∼3.8 μm. The typical barrier-shaped distribution may be mainly due to the nuclear energy deposition of the incident ions into the substrate. By performing a modal analysis on the observed TE modes, it was found that the TE 0 and TE 1 modes can be well-confined inside the waveguide.

Active planar waveguides based on sol–gel Er 3+-doped SiO 2–ZrO 2 for photonic applications: Morphological, structural and optical properties

Er 3+-doped glass-ceramic SiO 2–ZrO 2 optical planar waveguides were prepared by the sol–gel route using different SiO 2:ZrO 2 molar ratios (90:10, 85:15, 80:20 and 75:25). Multilayered films were deposited onto Si(1 0 0) substrates by the dip-coating technique. Structural characterization was performed using vibrational spectroscopy and X-ray diffraction. Some optical properties, densification and surface morphology of these films were investigated as a function of the SiO 2:ZrO 2 ratio, annealing temperature and time. Optical properties such as refractive index, number of propagating modes and attenuation coefficient were measured at 632.8, 543.5 and 1550 nm, by the prism coupling technique. Uniform surface morphology with roughness less than 0.5 nm. Low losses, less than 0.9 dB/cm at 612.8 nm in the TE 0 mode, were measured for the planar waveguides containing up to 25 mol% zirconium oxide. Luminescence of Er 3+ in the near infrared was observed for the active nanocomposite.

Low‐dose ion implanted active waveguides in Nd3+ doped near‐stoichiometric lithium niobate: promising candidates for near infrared integrated laser

AbstractBy applying low‐dose oxygen ion implantation, active planar waveguides in Nd3+ doped near‐stoichiometric lithium niobate laser crystals have been, for the first time to our knowledge, successfully produced. The waveguide exhibits good transmission properties with relatively low propagation loss of ∼2 dB/cm. The confocal micro‐luminescence investigations indicate that the emission properties of Nd3+ ions in the waveguide are well preserved with respect to the bulk, thus showing promising potentials for efficient waveguide laser action operating at the Nd3+ near‐infrared bands. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Active waveguide in Nd3+:MgO:LiNbO3 crystal produced by low-dose carbon ion implantation

We report on Nd3+:MgO:LiNbO3 active planar waveguides produced by 3MeV carbon ion implantation at dose of 7.5×1014cm−2. The extraordinary refractive index of the sample surface experiences positive alternations after the implantation and subsequent thermal annealing treatment, constructing enhanced-well confined waveguide structures. The propagation loss of the waveguide is 1–2dB∕cm, which means acceptable quality for further guide-wave applications. The microluminescence spectra of the waveguide show fairly good potentials for laser action at 929 and 1085nm.

Nondestructive measurement of the propagation losses in active planar waveguides

A nondestructive loss-measurement method for active planar waveguides has been developed. It is based on the determination of the longitudinal distribution of fluorescence light along the waveguiding direction, obtained at different excitation wavelengths. First measurements have been performed on a 10 μm thick Nd:Sc2O3 waveguiding film, deposited on a sapphire substrate by pulsed laser deposition, and on a 35 μm thick diffusion-bonded Nd:YAG waveguide between sapphire layers. Their scattering losses have been determined to be (11.6±0.9) and (6.9±0.9) dB/cm, respectively.