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CO2 laser annealing on erbium-activated glass-ceramic waveguides for photonics
Abstract
a b s t r a c t Silica-based sol–gel waveguides activated by Er 3+ ions are one of the most important materials for inte-grated optics devices. In this paper, we present an alternative method combining sol–gel route and CO 2 laser annealing for planar optical waveguides processing. The effects of pulsed and continuous CO 2 laser irradiation on the optical and spectroscopic properties of SiO 2 –ZrO 2 and SiO 2 –HfO 2 planar waveguides are evaluated and the thermal conventional annealing effects for these systems are reported for compari-son. All the planar waveguides, doped with 0.5 and 5 mol% Er 3+ , were prepared by sol–gel route using dip-coating deposition on v-SiO 2 substrates. An increase of the refractive index of approximately 0.04 at 1.5 lm has been observed on 70SiO 2 –30HfO 2 planar waveguide after continuous CO 2 laser annealing. A similar refractive-index variation was detected in all SiO 2 –ZrO 2 planar waveguides after CO 2 laser irra-diation. We have observed, moreover, that continuous CO 2 laser annealing can lead to waveguides with a lower attenuation coefficient with respect to the attenuation coefficient measured for thermal annealed waveguides. Upon excitation at 514.5 nm continuous-wave laser light, on the irradiated sample, the shape is found to be almost independent on the time and irradiation power with CW laser annealing but a decrease of the FWHM of approximately 46–12 nm has been observed on planar waveguides after pulsed laser annealing. Before and after conventional thermal annealing, the 4 I 13=2 level decay curves present a single-exponential profile with a lifetime of 4.0 and 5.7 ms, respectively, but the lifetime increases up to 7.0 ms, after pulsed laser annealing treatment. X-ray diffraction and optical spectroscopy showed that after an adapted pulsed CO 2 laser annealing, the resulting materials showed a crystalline environment. Ó 2008 Published by Elsevier B.V.
... In fact, in order to produce active rare-earth nano-crystals in a glass matrix, heat treatment using a furnace is commonly used, but laser annealing process offers an effective and complementary fabrication method. Several types of lasers have been used for laser annealing, differing primarily in wavelength (e.g., XeCl at 308 nm, frequency doubled Nd-YAG at 532 nm, Nd-YAG at 1064 nm, CO 2 at 10.6 μm) [228]. Let us consider planar optical waveguides: CO 2 laser annealing has been used to reduce scattering losses in Corning 7059 glasses [226,229] and ZnO [230] thin-film waveguides fabricated on thermally oxidized silicon substrates, achieving losses as low as 0.05 dB/cm for Corning 7059 waveguides [226] and 0.01 dB/cm for ZnO ones [230]. ...
... Quite recently, interesting results have been obtained in the case of GeO 2 sputtered waveguides [227,233,234]. Laser processing was also successfully employed in SiO 2 · ZrO 2 and SiO 2 · HfO 2 planar waveguides, prepared by sol-gel route and activated by Er 3+ ions [228,235]. ...
... 80SiO2-20ZrO2 0.5 5 80SiO2-20ZrO2 0. 5 30 detailed AFM observations confirmed a decrease of the surface roughness but, at the same time, revealed that small spherical grains were produced on the surface by laser irradiation [242]. As previously mentioned, laser processing also improves the spectroscopic properties of the RE-doped GCs in respect to parent glasses [235,228]. This was proved in planar waveguides of silica-zirconia and silica-hafnia activated by Er 3+ ions and prepared by the sol-gel route according to the protocol reported in detail elsewhere [235,228]. ...
Glass-ceramics (GCs) are constituted by nanometer–to–micron-sized crystals embedded in a glass matrix; usually, their structural or functional elements (clusters, crystallites or molecules) have dimensions in the 1 to 100 nm range. As the name says, GCs must be considered an intermediate material between inorganic glasses and ceramics; in most cases the crystallinity is between 30 and 50%. GCs share many properties with both glasses and ceramics, offering low defects, extra hardness, high thermal shock resistance (typical of ceramics) together with the ease of fabrication and moulding (typical of glasses). The embedded crystalline phase, however, can enhance the existing properties of the matrix glass or lead to entirely new properties. GCs are produced by controlled crystallization of certain glasses, generally induced by nucleating additives; they may result opaque or transparent. Transparent GCs are now gaining a competitive advantage with respect to amorphous glasses and, sometimes, to crystals too. The aim of the present paper is to introduce the basic characteristics of transparent glass-ceramics, with particular attention to the relationship between structure and transparency and to the mechanism of crystallization, which may also be induced by selective laser treatments.
Their applications to the development of guided-wave structures are also briefly described.
... For laser annealing several types of lasers have been used, differing primarily in wavelength (e.g. XeCl 308 nm, frequency doubled Nd-YAG 532 nm, Nd-YAG 1064 nm, CO 2 10.6 µm) [4]. It was reported that CO 2 laser annealing can reduce scattering losses in Corning 7059 glasses [2] and ZnO [5] thin-film waveguides fabricated on thermally oxidized silicon substrates. ...
... Quite recently interesting results has been obtained in the case of GeO 2 sputtered waveguides [3,8,9]. Laser material processing technique was also successfully employed in SiO 2 -ZrO 2 and SiO 2 -HfO 2 planar waveguides, prepared by sol-gel route and activated by Er 3+ ions [10,4]. Another interesting example concerning specific modification of the luminescence properties induced by laser processing is reported in [11]. ...
... Crystallization of glass materials depends on several factors: chemical composition and viscosity of glass, basic material, mutual solubility of every component, duration of exposure on proper temperatures, existence of crystallization catalysts and conditions of thermal processing of glass. It was already mentioned that laser material processing can improve spectroscopic properties of the parent glass when rare-earth activated glass ceramics are developed [4,10]. The investigated samples were planar waveguides of silica-zirconia and silica-hafnia activated by Er 3+ ions and prepared by sol-gel route. ...
Transparent glass-ceramics, activated by luminescent species, present an important class of photonic materials because their specific optical, spectroscopic and structural properties. Several top-down and bottom-up techniques have been developed for transparent glass ceramic fabrication. Among them, laser material processing plays an important role and many significant results have been obtained in the field of waveguide glass ceramics fabrication. Here, after a short description of the state of art regarding laser material processing for glass ceramics, we report on the specific use of CO 2 laser for the fabrication of transparent glass ceramic waveguides.
... In recent years, we have demonstrated that RF-sputtering (RFS) is a suitable technique to fabricate optical planar waveguides and photonic microcavities operating in the visible and NIR regions91011. In order to produce transparent glass-ceramic, heat treatment employing a furnace is currently used, but recently efforts were performed for the development of alternative treatments like the laser annealing (LA) process especially for its advantages in terms of temporal and spatial annealing control121314. The CO 2 laser annealing has been successfully used to reduce scattering losses in different kinds of amorphous optical planar waveguides15161718, and for the fabrication of glass-ceramic coating [19] and glass-ceramic waveguides with low attenuation coefficient [14]. ...
... In order to produce transparent glass-ceramic, heat treatment employing a furnace is currently used, but recently efforts were performed for the development of alternative treatments like the laser annealing (LA) process especially for its advantages in terms of temporal and spatial annealing control121314. The CO 2 laser annealing has been successfully used to reduce scattering losses in different kinds of amorphous optical planar waveguides15161718, and for the fabrication of glass-ceramic coating [19] and glass-ceramic waveguides with low attenuation coefficient [14]. The characterization of the structure of the samples is crucial to assess the effect of the LA process and to determine the appropriate irradiation protocols. ...
... Comparing the refractive indices in the GeO 2 waveguides before and after LA we observe an increase of about 0.04 with the irradiation at all the wavelengths. Similar variations were obtained in other systems treated by CO 2 LA [14]. The laser annealing allowed significant reduction of the attenuation coefficients. ...
GeO2 transparent glass ceramic planar waveguides were fabricated by a RF-sputtering technique and then irradiated by a pulsed CO2 laser. The effects of CO2 laser processing on the optical and structural properties of the waveguides were evaluated by different techniques including m-line, micro-Raman spectroscopy, atomic force microscopy, and positron annihilation spectroscopy. After laser annealing, an increase of the refractive index of approximately 0.04 at 1.5 µm and a decrease of the attenuation coefficient from 0.9 to 0.5 db/cm at 1.5 µm was observed. Raman spectroscopy and microscopy results put in evidence that the system embeds GeO2 nanocrystals and their phase varies with the irradiation time. Moreover, positron annihilation spectroscopy was used to study the depth profiling of the as prepared and laser annealed samples. The obtained results yielded information on the structural changes produced after the irradiation process inside the waveguiding films of approximately 1 µm thickness. In addition, a density value of the amorphous GeO2 samples was evaluated.
... In recent years, we have demonstrated that RF-sputtering (RFS) is a suitable technique to fabricate optical planar waveguides and photonic microcavities operating in the visible and NIR regions91011. In order to produce transparent glass-ceramic, heat treatment employing a furnace is currently used, but recently efforts were performed for the development of alternative treatments like the laser annealing (LA) process especially for its advantages in terms of temporal and spatial annealing control121314. The CO 2 laser annealing has been successfully used to reduce scattering losses in different kinds of amorphous optical planar waveguides15161718, and for the fabrication of glass-ceramic coating [19] and glass-ceramic waveguides with low attenuation coefficient [14]. ...
... In order to produce transparent glass-ceramic, heat treatment employing a furnace is currently used, but recently efforts were performed for the development of alternative treatments like the laser annealing (LA) process especially for its advantages in terms of temporal and spatial annealing control121314. The CO 2 laser annealing has been successfully used to reduce scattering losses in different kinds of amorphous optical planar waveguides15161718, and for the fabrication of glass-ceramic coating [19] and glass-ceramic waveguides with low attenuation coefficient [14]. The characterization of the structure of the samples is crucial to assess the effect of the LA process and to determine the appropriate irradiation protocols. ...
... Comparing the refractive indices in the GeO 2 waveguides before and after LA we observe an increase of about 0.04 with the irradiation at all the wavelengths. Similar variations were obtained in other systems treated by CO 2 LA [14]. The laser annealing allowed significant reduction of the attenuation coefficients. ...
GeO2 transparent glass ceramic planar waveguides were fabricated by a RF-sputtering technique and then irradiated by a pulsed CO2 laser. Different techniques like m-line, micro-Raman spectroscopy, atomic force microscopy, and positronbannihilation spectroscopy were employed to evaluate the effects of CO2 laser processing on the optical and structuralbproperties of the waveguides. The GeO2 planar waveguide after 2h of CO2 laser irradiation exhibits an increase of 0.04 inbthe refractive index, measured at 1542 nm. Moreover, the technique of laser annealing is demonstrated to significantlybreduce propagation loss in GeO2 planar waveguides due to the reduction of the scattering. Upon irradiation of the surfacebthe roughness decreases from 1.1 to 0.7 nm, as measured by AFM. Attenuation coefficients of 0.7 and 0.5 dB/cm at 1319 and 1542 nm, respectively, were measured after irradiation. Micro-Raman measurements evidence that the system embeds GeO2 nanocrystals and their phase varies with the irradiation time. Moreover, positron annihilation spectroscopy was used to study the depth profiling of the as prepared and laser annealed samples. The obtained results yielded information on the structural changes produced after the irradiation process inside the waveguiding films of approximately 1 μm thickness.
... Planar waveguides of silica-zirconia and silica-hafnia activated by Er 3+ ions were prepared by sol-gel route. Whole preparation protocol can be found in [7,8]. The starting solution, for both systems, was obtained by mixing ...
... It is well known that a crystalline environment around the rare earth induce a shortening in the phonon energies. Actually, the phonon energy of the surrounding environment of the rare earth ions is proportional to the non-radiation contribution of the 4 I 13/2 → 4 I 15/2 transition [8]. ...
... 112) and (020), respectively, and the phase is conserved even when the sample reaches room temperature. Like the yttria-stabilized zirconia (YSZ), the most common material used as the ceramic layer, this demonstrates the well-known stabilizing effect in the ZrO 2 structure, promoting the formation of high-purity tetragonal zirconia [19][20][21]. On the other hand, although the Al 2 O 3 /brass substrate sample displayed both α-brass and β-brass phases, compared with the Al 2 O 3 /SiO 2 -ZrO 2 /brass substrate, only α-brass was still observed [22]. ...
This work presents an analysis of the crystallization process and the influence of laser surface modification on the crystalline phases and optical responses of Al2O3/glass–ceramic coatings deposited on a brass substrate. We used a CO2 laser at different irradiation powers to change the structure of the superficial layer. The photoluminescence response enhanced the resolution of its line shape as the irradiation power increased. X-ray diffraction patterns exhibit the presence of different crystalline phases for the samples irradiated.
... Laser is one of the most important inventions of the twentieth century and continues to evolve in various fields and applications [1], since the first laser system manufacturing in the early sixties and the areas of the 2 use of laser is on the rise [2], and among the various applications is laser materials treatment, such as laser annealing process [3]. The oven heat treatment is using for annealing and production of nano-crystals, and laser annealing technique is promising technology for this purpose, where used several types of lasers different in wavelengths including carbon dioxide laser (CO2 laser) [4] which is characterized by a small amount of power with the good quality of consumption came out suitable for annealing [5]. Laser annealing has become one of the topics that have attracted the attention of researchers at the present time [6]. ...
Laser heat treatment is one of the important industrial applications of laser and being studied at the present time as a substitute for conventional thermal annealing. In this research (CuO) thin films have been deposition on a glass by (Sol-Gel / Spin Coating) technique and annealed by two ways, the first one using a convection oven, where they were annealing with three temperatures (400 °C, 500 °C, 600 °C) for one hour, and the second way using a continuous (CO2) laser with (10.6 μm) wavelength and (10 W) power and three intervals (10 min, 15 min, 20 min), were studied structural and optical properties of membranes prepared by both ways to determine the effect of laser annealing on them, and the results of (XRD) tests showed that these membranes with the structural of multi-crystalline monoclinic type and increase the degree of oven annealing temperature, as well as increasing the duration of the laser annealing lead to increased volumes of granular membranes rates. The results of the (AFM) tests to the topography of the surfaces of the membranes to be of crystalline uniformity and homogeneity superficially good, especially for laser annealed membranes. The results of optical examinations of these membranes showed that they having high permeability, especially in the regions of the visible spectrum and the near-infrared and increased with increase the degree of oven annealing temperature and the duration of laser annealing, and less energy gap of these membranes values with increase the temperature degree of annealing or increase of laser annealing time. In addition to this, the optical properties studied in this research included absorbance, reflectivity, refractive index, coefficients of absorption and extinction, and real and imaginary dielectric constants.
... The thermal stress between the fiber core and cladding can be modified using CO2-laser annealing [9,10]. The CO2 laser has also been useful in thermal annealing of semiconductors [11] and glass waveguides [12]. Since many applications employing fiber Bragg gratings, such as accurate wavelength-control devices in the telecommunication industry, require Bragg gratings with stabilized optical properties to support long-term usage, it is essential to study the decay characteristics of these Bragg gratings. ...
The thermal endurance of fiber Bragg gratings (FBGs), written with the aid of 193-nm ArF excimer laser irradiation on H2-loaded Ge/B codoped silica fiber, and pretreated with a CO2 laser and a subsequent slow cooling process, is investigated. These treated gratings show relatively less degradation of grating strength during the thermal annealing procedure. The thermal decay characteristics of treated and untreated fiber, recorded over a time period of 9 hours, have been compared. The effect on the Bragg transmission depth (BTD) and the center-wavelength shift, as well as the growth of refractive-index change during the grating inscription process for both treated and untreated fiber, are analyzed.
... Rare earths (RE)-doped materials have been extensively studied for many applications, including flat panel displays [1][2][3][4][5], fiber optics [6][7][8][9][10], solar cells [11,12], lasers [13][14][15], and others [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Among RE-doped materials for applications on lamps, lasers and flat panel displays, the Eu 3 þ -doped Y 2 O 3 has received considerable attention due to intense photoluminescence emission in the red region of the electromagnetic spectrum [32][33][34][35][36]. ...
Herein we report on the crystallized nanoparticles based on Eu3+-doped Y2O3 with 5 mol% using citric acid as precursor. The heating temperatures were evaluated in order to obtain the best crystallized nanoparticles with size around 12 nm and with highest red intense photoluminescence emission. Nanocrystallite size was calculated by Scherrer׳s equation based on diffractogram of the material heated at 750 °C for 4 h, obtaining size around 8 nm. The low photoluminescence intense emissions were attributed to the presence of quenchers remaining from precursors used in the synthesis. In general the photoluminescence properties were evaluated based on emission and excitation spectra profile. Rietveld refinement was performed based on the diffractogram of the material annealed at 750 °C for 4 h, and the visualization of the cubic structure was obtained. The centered cubic crystalline structure of Y2O3 was obtained and the photoluminescence properties of Eu3+ ion in Y2O3 host lattice was verified as being dependent on the temperature of heating and C2 and S6 site of symmetry present in the cubic structure. CIE chromaticity diagram was obtained with x and y being 0.682 and 0.316, respectively, for material with the highest relative photoluminescence intensity.
... Other than that, the uses of CO 2 laser for FBG annealing and phase-shifted FBG fabrications have also been reported [21,22] There are a variety of commercially available heating elements and furnaces that are capable of 100 °C up to 1600 °C, suitable for the purposes of thermal annealing process and characterization of the produced RFBG. Mid-infrared laser source such as CO 2 laser is also found useful for thermal annealing of semiconductors [23], glass fibers and glass waveguides [24]. With the assistance of sapphire crystal that has high absorbance for CO 2 laser (10.6 μm), it can serve as a mini furnace and it is capable of reaching the melting point of silica glass [25]. ...
In this work, we have demonstrated for the first time grating regeneration in hydrogenated fibers by direct CO2 laser annealing. During the annealing process, the center wavelength redshifts as the intensity of the focused CO2 laser on the grating is elevated. The reflectivity of the grating begins to decay as the temperature induced in the grating approaches the erasure temperature. The grating is completely erased and regenerated afterwards. The observed spectral results have provided the proof of occurrence of dehydroxylation and stress relaxation in the fiber core during the annealing process. Regenerated gratings with low loss, good temperature sensitivities and sustainability have been successfully developed by this technique.
... 45 GC WGs are produced by a suitable thermal treatment; laser annealing too may be quite effective. 46 They are characterized by high transparency in the cerammed state and by the fact that rare-earth dopants are preferentially incorporated into the crystals, so that the emitting ions experience a lower phonon energy environment than in the glass matrix. The propagation losses of GCs depend, as usual, on absorption and scattering: absorption can generally be reduced to acceptable levels by purification of the starting materials and by careful melting practices; scattering, on the contrary, is not easily eliminated in glasses, and a general theory describing the relationship between structure and transparency in GCs is still under investigation. ...
Glasses, either pure or suitably doped, constitute an excellent material for the development of integrated optical circuits. A brief review is presented of the most widely used processes for the fabrication of passive and active glass waveguides. Brilliant prospects of glass-based platforms for the development of photonic integrated circuits are outlined. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Glass–ceramics are a class of materials with immense potential for many applications. Glass–ceramics, synthesized with appropriate composition and crystallized using a suitable heat-treatment protocol can have many important properties such as their optical, mechanical, thermal, chemical, and dielectric behavior tailored to particular values. The last decade has witnessed a global demand for improved of energy efficiency and the requirement to develop new green energy sources. Also, new, low-cost materials are needed: (i) that can better exploit light by performing existing photonic functions more efficiently and (ii) to create new devices. Glass–ceramics by virtue of their unique combination of properties can fill the need for energy storage and photonic applications. Starting with a short introduction to this class of materials, the chapter summarizes the state-of-the-art and the prospects for progress for dielectric, energy storage, and photonic applications of some recently developed novel glass–ceramics.
Grating regeneration using CO₂ laser has been demonstrated. Bragg wavelength redshifts as the irradiated laser power is elevated. The grating reflectivity begins to decay as the induced temperature is approaching the erasure temperature. The grating is completely erased and regenerated afterward.
This work reports on the Yb3+ ion addition effect on the near infrared emission and infrared-to-visible up conversion from planar waveguides based on Er3+-Yb3+ co-doped Nb2O5 nanocrystals embedded in SiO2-based nanocomposite prepared by a sol-gel process with controlled crystallization in situ. Planar waveguides and xerogels containing Si/Nb molar ratio of 90:10 up to 50:50 were prepared. Spherical-like orthorhombic or monoclinic Nb2O5 nanocrystals were grown in the amorphous SiO2-based host depending on the niobium content and annealing temperature, resulting in transparent glass ceramics. Crystallization process was intensely affected by rare earth content increase. Enhancement and broadening of the NIR emission has been achieved depending on the rare earth content, niobium content and annealing temperature. Effective Yb3+→Er3+ energy transfer and a high-intensity broad band emission in the near infrared region assigned to the Er3+ ions 4I13/2→4I15/2 transition, and longer 4I13/2 lifetimes were observed for samples containing orthorhombic Nb2O5 nanocrystals. Intense green and red emissions were registered for all Er3+-Yb3+ co-doped waveguides under 980nm excitation, assigned to 2H11/2→4I15/2 (525nm),4S3/2→4I15/2 (545nm) and 4F9/2→4I15/2 (670nm) transitions, respectively. Different relative green and red intensities emissions were observed, depending upon niobium oxide content and the laser power. Upconversion dynamics were determined by the photons number, evidencing that ESA or ETU mechanisms are probably occurring. The 1931 CIE chromaticity diagrams indicated interesting color tunability based on the waveguides composition and pump power. The nanocomposite waveguides are promising materials for photonic applications as optical amplifiers and WDM devices operating in the S, C, and L telecommunication bands; and as upconverter materials for visible upconversion lasers, biomedical applications, energy conversion for solar cells and others.
The obtention of efficient and compact light sources based on silica doped with rare earth (RE) ions demands high emission yields, which require a good dispersion of RE ions. Glass-ceramics, associating a glass with nanocrystals (NCs), allow such a dispersion and still assure adequate optical transparency. In addition, the NCs have broad absorption bands and can transfer their energy to the RE ions, thus improving the emission efficiency. In this work, silica-based ceramics containing SnO<sub>2</sub> NCs were prepared as thin films and bulk by the sol-gel technique. The optical and structural properties of the thin films were compared with those of monoliths. Several parameters, such as the maximum concentration of tin, the temperature of crystallization and of densification, differ according to the morphology of the materials. The interaction between the silica matrix and SnO<sub>2</sub> NCs was studied by combining several analytical techniques such as vibrational spectroscopies, XRD,TEM, porosimetry BET...The addition of tin retards the densification of the matrix, leaving a residual porosity. The luminescence of Er<sup>3+</sup> and Eu<sup>3+</sup> (emission bandwidths, lifetimes) clearly shows the existence of two types of host sites, one crystalline and the other amorphous. Finally, the SnO<sub>2</sub> NCs promote the dispersion of the RE ions, leading to longer lifetimes and an energy transfer between crystal and RE.
Higher doping of
Er
3+
in glass
ceramic
waveguides would cause concentration and pair‐induced quenching which lead to inhomogeneous line‐width of luminescence spectrum thus reduce output intensity. Concentration quenching can be overcome by introducing
ZrO
2
in the glass matrix while co‐doping with
Yb
3+
which acts as sensitizer would improve the excitation efficiency of
Er
3+
.
In this study,
SiO
2
‐
ZrO
2
planar waveguides having composition in mol percent of
70
SiO
2
‐30
ZrO
2
doped with
Er
3+
and co‐doped with
Yb
3+
,
were prepared via sol‐gel route. Narrower and shaper peaks of PL and XRD shows the formation of nanocrystals. Intensity is increase with addition amount of
Yb
3+
shows sensitizing effect on
Er
3+
.
This paper presents the new material which replaces the existing core of an optical waveguide. Silver nanoparticles and silver zirconia composite were prepared by using various methods. The produced composite was sintered at 300°C. Then the nanocomposite was dispersed in the silica matrix. The resultant solution coated on the glass substrate by spin coating and produce slab structured optical waveguide. The thickness and refractive index were studied. The measured propagation losses were 9.9 dB/cm and 12.8 dB/cm for 650 nm and 830 nm wavelength, respectively. Methods of improving the quality of the waveguide are discussed.
Rare earth-activated glass-ceramic waveguides constitute a potential significant system to behave as an effective optical medium for light propagation and luminescence enhancement. We present a review on fabrication and optical, structural, and spectroscopic characterization of some kind of rare earth activated oxide glass-ceramic waveguides, obtained by sol-gel route with both bottom-up and top-down approaches, and fluoride glass-ceramic waveguides fabricated by physical vapor deposition. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3559211]
SiO2—GeO2 planar waveguides, doped with Eu ions, have been prepared using the dip-coating technique. Optical characterization of the waveguides has been performed by m-line spectroscopy. The structural modification occurring during the densification process has been followed by waveguide Raman and luminescence spectroscopies. A strong rearrangement in the glass occurs after annealing at 900°C and the final structure appears more ordered.
Radio-frequency sputtering was used to prepare silica-titania planar waveguides, doped with Er. The films, deposited on a silica substrate, were activated with different concentrations of erbium (0.14-1.63 at.%), starting from metallic erbium. The refractive indices, the thickness and the propagation losses of the waveguides were measured. Structural information about the deposited film were obtained by waveguide Raman spectroscopy. Waveguide luminescence spectroscopy was used to investigate the spectroscopic properties of the active ion, such as the green to blue upconversion and the emission at 1.5 μm, in this system. The dependence of the dynamical processes on the erbium content was studied.
Thin-film integrated optics is becoming more and more important in optical-communications technology. The fabrication of passive devices such as planar optical waveguides, splitters, and multiplexers is now quite well-developed. Devices based on this technology are now commercially available. One step to further improve this technology is to develop optical amplifiers that can be integrated with these devices. Such amplifiers can compensate for the losses in splitters or other optical components, and can also serve as pre-amplifiers for active devices such as detectors.
In optical-fiber technology, erbium-doped fiber amplifiers, are used in long-distance fiber-communications links. They use an optical transition in Er ³⁺ at a wavelength of 1.54 μ m for signal amplification, and their success has set a standard of optical communication at this wavelength. Using the same concept of Er doping, planar-waveguide amplifiers are now being developed. For these devices, silicon is often used as a substrate, so that optoelectronic integration with other devices in or on Si (electrical devices, or Si-based light sources, detectors, and modulators) may become possible. Figure 1 shows an example of a silicon-based optical integrated circuit5 in which a 1 × 4 splitter is combined with an amplifying section.
Significant reductions in the optical scattering losses of Si 3N 4, Nb 2O 5, and Ta 2O 5 waveguides fabricated on SiO 2 /Si substrates have been measured following CO 2 laser annealing. The largest improvements were observed for Si 3N 4 waveguides, where waveguide attenuation values of about 6.0 dB/cm before laser annealing were reduced to as low as 0.1 dB/cm afterwards. An improvement of more than an order of magnitude was obtained for a Nb 2O 5 waveguide upon laser annealing, the attenuation coefficient decreasing from 7.4 to 0.6 dB/cm. In the case of one Nb 2O 5 waveguide no improvement was obtained upon laser annealing. The attenuation coefficient of a reactively sputtered Ta 2O 5 waveguide was found to decrease from 1.3 dB/cm before laser annealing to 0.4 dB/cm afterwards. In the case of a thermally oxidized Ta 2O 5 waveguide a small initial improvement in waveguide attenuation was followed by degradation upon further laser annealing.
Sol-gel SiO2 - TiO2 multilayers (containing 20 mol% TiO2) have been deposited by spin-coating onto single crystal Si substrates previously covered with a SiO2 buffer layer (approximately 4 micrometers), also prepared by sol-gel. The silica-titania films were first densified at 900 degrees Celsius and were then subjected to selected crystallization heat treatments at 1000 degrees Celsius, in order to precipitate different volume fractions of anatase (TiO2) crystallites, between 2.5 and 15%. The optical loss of these nanocomposites was measured at different wavelengths, using argon ion and He-Ne laser light. The experimental loss values, after removing the intrinsic Rayleigh term and surface scattering, were compared to scattering losses calculated by means of the Rayleigh-Mie theory, for light scattering by spherical particles, which was used to examine the influence of different parameters: radiation wavelength, nanocrystallite size and volume fraction of nanocrystals. The theoretical calculations show that, for the wavelengths of interest ((lambda) on the order of or greater than 1 magnitude), nanocrystallite scattering losses remain below 0.5 dB/cm, even for volume fractions as high as 15%, as long as their diameter is below 11 nm. The experimental results agree reasonably well with the theoretical predictions, considering the approximations made. The extension of the model to the study of residual film porosity led to the conclusion that typical porosity present has a negligible influence on the total waveguide loss.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Silica-hafnia glass-ceramics waveguides activated by Er3+ ions were fabricated by sol-gel route. X ray diffraction and optical spectroscopy showed that after an adapted heat treatment, the resulting materials showed a crystalline environment. Analysis of the luminescence properties has demonstrated that erbium ions are, at least partially, trapped in a crystalline phase. Losses measurements at different wavelength highlight a very low attenuation coefficient indicating that this nanostructured material is suitable for a single band waveguide amplifier in the C band of telecommunication.
We describe the preparation and characterization of zirconia based planar waveguides. The sol-gel technique allowing the preparation of glass films at room temperature was applied. Zirconium propoxide and organically modified silicates (ORMOSIL's) were used as precursors. Acetic acid was used as a chelating agent to stabilize the zircona precursor. Films were prepared by dip coating on the glass substrate. Multimode light guiding was demonstrated in the films. The properties of films: refraction index, thickness and transparency were studied. The refractive index of 1.69 allows trapping of the light allowing its guidance. In order to produce active waveguides, films were doped by laser dyes; Rhodamine B, LFR 300 (red perylimide dye), Pyrromethene 567 and LDS 730. The UV-vis and fluorescence spectra of dopants were measured. The possibility of the use of the active waveguides for optical and laser applications was shown.
Application of a surface coating to Corning 7059 glass thin‐film optical waveguides has been shown to significantly reduce their scattering loss. Combining the technique of CO 2 laser annealing of glass waveguides with surface coating, we measure waveguide loss as low as 0.01 dB/cm. By attributing the decrease in attenuation to elimination of the effects of surface irregularities, we were able to identify surface and bulk contributions to scattering losses in the original waveguide. By making such an identification before and after laser annealing, we confirm that CO 2 laser annealing of glass waveguides reduces both surface and bulk contributions to scattering losses.
We report successful laser annealing of ZnO optical waveguides deposited on an amorphous SiO 2 layer thermally grown on Si. A significant improvement in the optical attenuation of the fundamental mode from several dB/cm before laser annealing to as low as 0.01 dB/cm after laser annealing is observed. Scattering loss measurements for the m = 1 and m = 2 mode are also reported. We attribute the reduction in loss primarily to an improvement in the quality of the ZnO film in the region near the ZnO‐SiO 2 interface.
Laser annealing with a CO 2 laser is utilized to improve the quality of Corning 7059 glass thin‐film optical waveguides. The 1.0‐μm‐thick 7059 glass film is deposited by sputtering onto a thermally oxidized silicon substrate. Measurement of the absorption coefficient of 7059 glass at λ = 10.6 μm yields a value of 1.12 x 10<sup>4</sup> cm<sup>-1</sup>. Dark‐field photomicrographs taken before and after laser annealing imply that both surface defects and bulk inhomogeneities are removed by laser annealing. Waveguide attenuation is measured to be 17.4 dB/cm befor laser annealing and 0.6 dB/cm afterwards.
Significant reductions in the optical scattering losses of Si 3 N 4 , Nb 2 O 5 , and Ta 2 O 5 waveguides fabricated on SiO 2 /Si substrates have been measured following CO 2 laser annealing. The largest improvements were observed for Si 3 N 4 waveguides, where waveguide attenuation values of about 6.0 dB/cm before laser annealing were reduced to as low as 0.1 dB/cm afterwards. An improvement of more than an order of magnitude was obtained for a Nb 2 O 5 waveguide upon laser annealing, the attenuation coefficient decreasing from 7.4 to 0.6 dB/cm. In the case of one Nb 2 O 5 waveguide no improvement was obtained upon laser annealing. The attenuation coefficient of a reactively sputtered Ta 2 O 5 waveguide was found to decrease from 1.3 dB/cm before laser annealing to 0.4 dB/cm afterwards. In the case of a thermally oxidized Ta 2 O 5 waveguide a small initial improvement in waveguide attenuation was followed by degradation upon further laser annealing.
Sol-gel derived glass-ceramic waveguides for optical amplification
- Y Jestin
- C Armellini
- S N B Bhaktha
- A Chiappini
- A Chiasera
- S Diré
- M Ferrari
- C Goyes
- M Montagna
- E Moser
- G Conti
- S Pelli
- G C Righini
- C Tosello
- K C Vishunubhatla
Y. Jestin, C. Armellini, S.N.B. Bhaktha, A. Chiappini, A. Chiasera, S. Diré, M.
Ferrari, C. Goyes, M. Montagna, E. Moser, G. Nunzi Conti, S. Pelli, G.C. Righini, C.
Tosello, K.C. Vishunubhatla, Sol–gel derived glass–ceramic waveguides for
optical amplification, Oral communication V Workshop Italiano Sol–Gel,
Milano, Italy, June 2006.
Optical loss mechanisms in nanocomposite sol–gel planar waveguides
- Almeida