Proceedings Volume 3620

Integrated Optics Devices III

Giancarlo C. Righini, S. Iraj Najafi
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Proceedings Volume 3620

Integrated Optics Devices III

Giancarlo C. Righini, S. Iraj Najafi
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 26 March 1999
Contents: 11 Sessions, 43 Papers, 0 Presentations
Conference: Optoelectronics '99 - Integrated Optoelectronic Devices 1999
Volume Number: 3620

Table of Contents

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Table of Contents

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  • Devices for Optical Telecommunications and WDM
  • Modulators and Switches
  • Coupler Structures
  • Electro-Optical Devices
  • Modeling and Characterization I
  • Sol-Gel Waveguides and Devices
  • Ion-exchanged Waveguides and Devices
  • Materials, Fabrication, and Testing
  • Modeling and Characterization II
  • Sensors
  • Poster Session
  • Sensors
Devices for Optical Telecommunications and WDM
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Challenges and opportunities for integrated optics in optical networks
Ever-increasing needs for more telecommunication bandwidth have brought about the recent emergence of WDM technology as a commercial reality with a very substantial volume, and prospects for near future development of optical networking. The new optical functionalities in networks will also provide conmiercial opportunities for integrated optics, which have been yearned for a long time. Integrated optics must meet the new challenges of fulfilling the strict performance, reliability and cost requirements for applications in the field. Integrated optics community is experiencing a transition to a new era, with their work moving from research laboratories to industrial production. Various expected applications for integrated optics devices in the areas of wavelength division multiplexing, optical modulation, optical switching, wavelength conversion and others are reviewed. General views on development of packaging technologies, component design and testing are also included.
Electro-optic ADD-DROP tunable filter based on asymmetric directional coupler
David Brooks, Shlomo Ruschin
A novel electro-optic integrated ADD-DROP tunable filter, for multiwavelength communication fiber-based networks was designed, realized and characterized. The device is a fast four port active tunable filter, which consists of an symmetric multielectrode co-directional coupler based on a two step Ti:LiNbO3 technology. The filter has a FWHM from 6 nm to 16 nm with a conversion efficiency of unity in the entire tuning range (750 - 900 nm). Feasible modification of the device can narrow significantly the main lobe width and suppress side bands.
Cross talk reduction in switching networks by asymmetrical off-on switches
Winfried Bernhard, Roland Mueller-Fiedler, Thomas Pertsch, et al.
A new off-on switching scheme is introduced which blocks a waveguide path in the passive off-state and transmits the signal in the active on-state. The operating principle is based on the self-diffraction of a narrow guided beam when it escapes from a waveguide with two dimensional confinement into a region of appropriate length with at most one dimensional confinement. In particular a remaining interface of the initial waveguide superimposes reflection, which in sum results in a very efficient asymmetrical blow out of the guided power. In the active on-state, low-loss waveguiding is sustained when an electrode causes an appropriate refractive index change, e.g. due to the thermo-optical effect. Thus the signal is received in the output waveguide, an identical pendant of the input guide. The switching behavior is almost digital, and the wavelength dependence is minimal only. This makes the device useful for switching and modulation in a multi-wavelength optical network. Calculations show on-off signal ratios of better than 30 dB e.g. in polymeric waveguide configuration of 3 mm length. This is nicely adapted to the demands of crosstalk reduction in switching networks. Experimental results from a thermo-optic polymer waveguide device with 32 dB off-state attenuation and 0.8 dB on-state excess loss fit well to the data obtained from the numerical modeling.
Modulators and Switches
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Applications of lithium niobate integrated optic in telecommunication systems
Sergio S. Bosso
In the last few years the advent of D-WDM systems based on Erbium Doped Fiber Amplifiers (EDFA) has pushed Lithium Niobate technology towards massive field deployment, generating an abrupt increase of production volumes of 2.5 Gbit/s amplitude modulators. The evolution of the new systems up to 10 Gbit/s transmission speed, is now asking for larger bandwidth modulators. Simultaneously the research in the laboratories is working on the development of new component families. As an example, in the area of modulators, a new device has been recently introduced to the market, integrating (on the same chip) a variable attenuator with the 2.5 Gbit/s modulator, to allow individual channel pre-equalization. Other very promising functionalities can be implemented using Acousto-Optical Tunable Filters (AOTF's). Taking advantage of their fast tuning speed, Optical Channel Analyzers (OCA) can be made allowing full EDFA spectrum scanning time of the order of few milliseconds. Finally new applications are coming for the electro-optical switching matrices. Due to their high switching speed, these components can be used for routing and protection functions in new photonic networks.
Intracavity optical modulation using Fresnel zone-plate-type E-O lens
Satoshi Tanaka, Heihachi Sato
Setting an electrically controllable dual focal-point (DFP) lens into the optical resonator of a laser, we can readily modulate the output power of the optical beam with a relatively low voltage. The DFP lens is fabricated by combining an electro-optic (E-O) material with the Fresnel zone-plate (FZP) lens, in which numerous transparent (ITO) electrodes are evaporated in the form of the Fresnel zone- plate (FZP) on a PLZT ceramic E-O plate to compose a dual focal-point lens with and without an applied voltage. In addition, the PLZT (La/Zr/Ti equals 9/65/35) ceramic used here as an E-O material represents a quadratic E-O effect. Inserting this DFP E-O lens inside the optical resonator of an He-Ne 3.39 mm laser on trial, the fundamental modulation characteristics are investigated. As a result, about 15.5% modulation degree was obtained with applying the rf (2 kHz) voltage of 13.5 Vp under a certain bias. The operational principle is experimentally demonstrated together with theoretical discussions.
Double quantum well phase modulators using surface acoustic waves
Wallace C. H. Choy, E. Herbert Li, Bernard L. Weiss
Electro-optic modulators using the interaction of surface acoustic waves (SAWs) with III-V semiconductor multiple quantum well structures have gained interests. A SAW induces potential field which provides the phase modulation. In order to improve the phase modulation, an AlGaAs/GaAs asymmetric double quantum well (DQW) optical phase modulator using SAWs is investigated theoretically. The optimization steps of the DQW structure are discussed. The optimized phase modulator structure is found to contain a five-period DQW active region. Analysis of the modulation characteristics show that by using the asymmetric DQW, the large change of the induced potential at the surface and thus large modification of the QW structure can be utilized. The modification of each QW structure is consistent, although this consistency is not always preserved in typical SAW devices. Consequently, the change of refractive index in each of the five DQWs is almost identical. Besides, the change of effective refractive index is 10 times larger here in comparison to a modulator with a five periods single QW as the active region and thus produces a larger phase modulation. In addition, a long wavelength and a low SAW power required here increase the size of the SAW transducer and simplify its fabrication.
Fast tunable filter enables packet switching on all-optical network
Nina L. Taranenko, Stephen C. Tenbrink, Vladimir Katsman, et al.
A fast tunable filter enables a different switching technology to be implemented for an all-optical network. The fiber Fabry- Perot tunable filter works fast enough (three orders of magnitude faster than commercially available Fabry-Perot filters) to allow packet switching to be implemented on an experimental all-optical wavelength-division-multiplexed packet-switched network. The system uses a broadcast-and- select design, in which each node transmits at a Gb/s at dedicated wavelength. The data is transmitted over the passive-star network to all other nodes. The receiver at each node scans through all the wavelengths and selects signals addressed for that node. The major challenge of combining packet switching with the optical network is the tuning at the receiver that must be performed in microseconds, as opposed to milliseconds. The use of the optical filter provides a technical breakthrough for the bottleneck of high-speed packet switching. Another challenge of fast optical packet switching is clock-recovery and synchronization of the packets. Conventional circuits are inadequate when a fast clock recovery for the short length packets is required because they need thousands bits to lock on. We have developed a system for fast clock recovery on packet-by-packet basis using a surface acoustic wave filter for narrow band filtering. The combined optical and electronic components recover the clock circuit as fast as several hundred bits.
Coupler Structures
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Wave-matching simulations of integrated optical coupler structures
Manfred Lohmeyer, Norbert Bahlmann, Oleksandr Zhuromskyy, et al.
One of the principal tasks of numerically simulating integrated optical devices is the accurate calculation of modal fields and propagation constants. Our recently proposed 'wave-matching-method' for dielectric waveguides with rectangular and piecewise constant refractive index profiles is based on expansions of the electromagnetic field into functions with harmonic and exponential dependence on the transverse coordinates. Local expansions for regions with constant permittivity are joined by minimizing a least squares expression for the remaining misfit at the discontinuity lines. For this paper the wave-matching analysis has been applied to a number of more complex structures: a conventional, deeply etched two-waveguide coupler, an ARROW- waveguide, a three dimensional four-waveguide coupler and three-waveguide coupler with multimode central rib (radiatively coupled waveguides). We have found good overall agreement where a direct comparison with published results is possible.
Grating couplers using silicon-on-insulator
Martin Tze Wei Ang, Graham T. Reed, Adrian P. Vonsovici, et al.
In integrated optics, grating couplers are used when conventional end-fire methods are cumbersome and less efficient in coupling light in and out of thin-film waveguides. Our aim is to fabricate a high efficiency grating coupler for integrated optics applications at infra-red wavelengths and for thin-film waveguides which can be used for sensor applications. In this paper, theoretical output efficiencies of silicon (Si) rectangular, ideal right-angled blazed and non-ideal trapezoidal gratings are presented. Using perturbation theory, Si rectangular gratings with optimum grating heights exhibit a maximum predicted output efficiency towards the surface at the order of 80% and Si right-angled blazed gratings have predicted efficiencies approaching 100%. The fabrication method consists of using electron beam lithography and reactive ion etching. Ion beam milling is also considered with the aim of creating blazed profiles by tilting the silicon-on-insulator (SOI) wafer. In our work, smart cut SOI Unibond wafers are used as the base material for fabricating the grating couplers as they offer good flexibility in choosing the guiding layer and buried layer thickness'. These waveguides are chosen to have an Si film thickness of 0.92 micrometer and an SiO2 buried layer thickness of 0.67 micrometer in order to use the transverse resonance effect to improve the output coupling efficiency. Si rectangular with various grating heights, designed at the first order of diffraction, were fabricated and characterized. The highest efficiency grating yet reported in SOI was produced, having the coupling efficiency in excess of 70%.
Numerical modeling of passive duplexers using the finite-element method
A new technique is presented for the design and characterization of passive duplexers employing multimode interference-based devices with two-dimensional confinement using silica-on-silicon technology. The size of the device is compared with that from previously published results, based on directional couplers, and the proposed design is shown to be shorter. The polarization and the cross-talk properties of such multimode interference-based devices have also been verified as being satisfactory.
Facet reflectivity of waveguides buried at realistic depths
Ana Vukovic, Phillip Sewell, Trevor Mark Benson, et al.
A novel method is applied to the facet reflectivity of a two dimensional waveguides not deeply buried into the cladding. The reflectivity of an angled two dimensional waveguide, with and without antireflection coatings is studied. It is shown that waveguides with AR coatings are more prone to the presence of the semiconductor-air boundary in which case the buried depth has to be taken into account.
Si3N4/SiO2/Si waveguide grating for fluorescent biosensors
Guy Voirin, Daniel Gehriger, Olivier M. Parriaux, et al.
The simulation of the coupling efficiency of fluorescence sources immobilized in the evanescent field of a waveguide mode has allowed the dimensioning of a sensing waveguide platform based on a silicon substrate exhibiting maximum fluorescence efficiency. The incoupling of the excitation light and the outcoupling of the fluorescence signal are performed by means of a corrugation grating. The presence of the highly reflective silicon surface under the waveguide grating causes interferences in the fluorescence output signal which depend on the wavelength and on the radiation angle. A theoretical modeling of the grating coupling under these conditions has led to the achievement of high incoupling efficiency at the excitation wavelength, and simultaneously to high outcoupling efficiency at the wavelength of the fluorescence peak. An experiment was performed with fluorescein at the surface of a 160 nm thick silicon nitride waveguide film on a silicon substrate with a 2100 nm thick buffer layer of silica. The measured outcoupled spectra fit well with the calculated spectra taking into account the output grating coupling, the fluorescence spectrum, and fluorescence coupling. These waveguide grating structures are applied to the detection of immunological reactions.
Electro-Optical Devices
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Low-cost integrated optical waveguide polarizer with an hybrid structure of birefringent polymer and ion-exchanged glass waveguide
Celia Sanchez Perez, Alain Morand, Pierre Benech, et al.
We report on a new type of glass ion-exchanged waveguide TE polarizer using an electro-optic polymer (conjugated PMMA-DR1) overlay. The polarization function is assured by poling the polymer in the vertical direction using a Corona process. An extinction ratio of 39 dB is obtained at the wavelength of (lambda) equals 1.3 micrometer. The insertion losses of the device are in order of 7 dB. The performance of the polarizer are investigated. Our experimental investigations show a polarization efficiency over than 40 dB.
Electro-optical behavior of an integrated device based on a liquid crystal waveguide
Lucia Petti, Pasquale Mormile, Massimiliano Furioso, et al.
The integrated optical devices represent the most innovative result of the research in the photonics field. New horizons can be open by introduction of new materials and advanced techniques. The applications depend on the properties of the considered materials and their response times to external applied field. In this article we present an integrated device in a three-stage planar waveguide, having as middle stage a nematic liquid crystal film. We studied the device performance with TE polarized input light. By a proper choice of the material parameters and of the driving voltages we got time response in the microsecond range. Our experimental results confirm the possibility of employing such a device working as optical switch and/or beam deflector. A further analysis is in progress in order to explain an anomalous electro-optical behavior occurred for higher applied voltages.
Transparent conductive sol-gel thin films for photonic applications
Terho K. Kololuoma, Juha T. Rantala, Jouko Vaehaekangas, et al.
Antimony doped tin dioxide (SnO2:Sb) thin films are fabricated by a new simplified sol-gel process. Films are prepared from an alcoholic solution of SnCl4(DOT)4H2O doped with SbCl3. Films are deposited by the spin coating process on sodalime glass, borosilicate glass, silicon wafers and ceramic alumina substrates. The chemical reactions during the heat treatment are monitored by DSC and TG. The chemical composition of the coatings are determined by scanning electron microscopy (SEM). Sheet resistance, Rs, is measured using a linear four-probe technique. Optical properties of the films are also determined. The resistivity of the thin films are presented as a function of the antimony doping level. The smallest sheet resistance of 200 (Omega) /$DAL is found for a 250 nm thick coating on a borosilicate substrate. It is observed that the sheet resistance does not decrease linearly with increasing film thickness. Fabrication possibilities of these materials for the integrated optics based sensors including patterning methods are discussed.
Low-voltage drive electro-optic Pb(Zr,Ti)O3 waveguide devices fabricated by solid-phase epitaxy
Keiichi Nashimoto, Shigetoshi Nakamura, Hiroaki Moriyama, et al.
Pb(Zr,Ti)O3 (PZT) thin film optical waveguides were grown on Nb-doped SrTiO3(100) substrates by solid-phase epitaxy to fabricate an electrode/waveguide/semiconductor structure. The substrates were spin-coated with methoxyethoxide precursor solutions and preannealed to form amorphous thin films followed by the solid-phase epitaxial crystallization of the thin films above 650 degrees Celsius. The grown epitaxial PZT waveguides had a single perovskite phase and a single (001) orientation. The propagation loss was reduced to 1.7 dB/cm by introducing an epitaxial buffer layer between the PZT waveguide and the Nb-doped SrTiO3 substrate. An electro- optic beam deflector was fabricated by sputtering an ITO prism electrode on the surface of the waveguide. Efficient laser beam deflection larger than 10 mrad was observed by applying 5 V between the prism electrode and the substrate. An index change higher than 0.001 at 5 V and an effective electro-optic coefficient larger than 40 pm/V were estimated from the deflection characteristic. For integrating the electro-optic PZT waveguide devices with passive waveguide components, channel waveguides and waveguide lenses were also fabricated in the PZT waveguides using a simple wet-etching process. These achievements suggest the realization of variety of low- voltage drive integrated waveguide devices including matrix switches as well as the deflectors.
Applications of lithium niobate and potassium titanyl phosphate integrated optic devices
Andreas S. Rasch, Eberhard Handrich
The most known active optical material is lithium niobate (LiNbO3). Due to the ferroelectric crystal structure lithium niobate changes its refractive index if an electric field is applied. Another ferroelectric material is potassium titanyl phosphate (KTP or KTiOPO4). KTP's properties also make it superior as an electro-optic modulator, in optical parametric generation, and in optical waveguiding. This paper will give an overview of production steps of integrated optics with proton exchange in lithium niobate and with ion exchange in potassium titanyl phosphate. Basic optic structures and components made for phase and intensity modulation are presented. The application of the integrated optic chips in sensors, telecommunication and color image generation will be addressed.
Modeling and Characterization I
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Modeling tools for integrated and fiber optical devices
Velko Peyov Tzolov, Dazeng Feng, Stoyan Tanev, et al.
This presentation will emphasize the current status of advanced design and simulation tools in photonics technology. The focus will be on Wavelength Division Multiplexing (WDM) component and integrated optic circuits modeling, although some aspects of optical link simulations will also be discussed. A wide variety of numerical methods such as the Beam Propagation Method (BPM), the Coupled Mode Theory (CMT), the Transfer Matrix Method (TMM), and the Finite-Difference Time Domain Method (FDTDM) in their state-of-the-art implementation will be presented. The results from simulating selected photonic components will be discussed.
Design and simulation tools for integrated optic circuits
Marcel F. van der Vliet, Gunter Beelen
In this paper we will present the recent trends in the development of design and simulation tools for integrated optical circuits. We will address the relevant design steps, required to finish a typical design cycle, such as technology simulations, optical simulations, and mask layout, as well as the vertical integration of these steps. A specific example is given with respect to the design process for a thermo-optical switch.
Rigorous study of leaky modes in optical waveguides
Muttukrishnan Rajarajan, S. S. A. Obayya, F. A. Fernandez, et al.
Accurate solutions of complex modes in leaky waveguides grown on low-cost silicon substrates are presented by using two rigorous numerical methods incorporating vectorial approaches. The optimization of waveguide parameters to restrict modal loss within a given limit and the study of mode filtering for multimode optical waveguides is also presented.
Sol-Gel Waveguides and Devices
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Nonlinear characterization of PbS nanocrystals embedded in sol-gel planar waveguides
Jochen Fick, Jochen Schell, Alessandro Martucci, et al.
Thin silica-titania planar waveguides doped with different concentrations of lead sulfide (10 - 25 mol%) have been prepared by a sol-gel process. It consist of three steps: (a) preparation of a colloidal sol of semiconductor particles; (b) preparation of an alkoxide solution, precursor of the glass- like matrix; (c) mixing of the colloidal sol and the alkoxide solution. Films were deposited on fused silica by dipping and densified for 1 h at 300 degrees Celsius in nitrogen. The mean particle size is 3 nm and the optical absorption edge is situated around 1100 nm. The nonlinear properties have been investigated using degenerated four wave mixing (DFWM) an a nonlinear m-line technique. Different Nd:YAG lasers with pico- and nanosecond pulses at 1064 nm have been used. Depending on the PbS concentration we measured a high negative nonlinear refractive index of n2 equals -3 to -9 10-8 cm2kW for nanosecond pulses (m-lines) and -1 to -10 10-10 cm2/kW for picosecond pulses (m-lines and DFWM). The response time of the nonlinearity is below 30 ps. All observed nonlinear effects are fully reversible and we did not observe any photodarkening. Straight, monomode channel waveguides have been fabricated on theses films.
Thin films of LiNb0.5Ta0.5O3 prepared on SiO2/Si substrates by sol-gel processing
Shi De Cheng, Chan Hin Kam, Yan Zhou, et al.
In this paper, we report the preparation and characterization of sol-gel derived thin films of LiNb0.5Ta0.5O3 on the silica-on silicon substrate. The solution is prepared by mixing LiOC2H5, Nb(OC2H5)5 and Ta(OC2H5)5 and the thin films are prepared using spin coating. The films are annealed at different temperatures of 400, 500, 600, and 700 degrees Celsius. Our X-ray diffraction study show that the films are amorphous when annealed at 400 degrees Celsius and are crystallized over 500 degrees Celsius. The crystallized films are slightly a-axis oriented. Nanocrystalline grains with the size of about several tens of nanometers are observed in the crystallized films under an atomic force microscope, making the films potential candidates for electro-optical/acousto-optical applications.
Fabrication of hybrid sol-gel glass diffractive elements
Juha T. Rantala, Pekka Ayras, Raviv Levy, et al.
Organically modified photosensitive hybrid glasses are synthesized and used for the fabrication of diffractive optical elements. The material synthesis is based on a sol-gel process. The materials are spin-deposited onto glass substrate that also have a significant role in the component assembly. The synthesized material has a negative tone property under UV-radiation and they can be patterned by a conventional UV- lithography process. Binary diffractive lenses are photoimprinted through an amplitude contact mask. Optical properties and surface roughness of the materials and elements are evaluated. Diffraction efficiencies of the elements are also measured. The process and material optimization for the reliable fabrication of integrated optics devices is carried out.
Ion-exchanged Waveguides and Devices
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Modeling and properties of an ion-exchanged optical variable attenuator
Xavier Orignac, Jan Ingenhoff, Norbert Fabricius
The optical signal power needs to be regulated at some locations in transmission lines. That can be done with the help of optical variable attenuators (OVA), devices which allows for the control of their insertion loss. This work describes the design and properties of some OVAs fabricated by the ion-exchange technique. The OVA functionality relies on a Mach-Zehnder structure, where the output optical intensity is tuned via the change in optical path along one of the two interferometer arms. Here, the optical path is varied through thermo-optic effect (change of refractive index with temperature). Modelling is first addressed: a mostly qualitative theoretical investigation is used to clarify how the fabrication parameters (burial depth and Mach-Zehnder arm separation distance) can be related to the OVAs properties (attenuation dynamic, switching power, settling time, PDL). Properties of fabricated OVAs are presented in a second part. They are compared with other existing products. The relationship between fabrication parameters and properties is also re-examined in light of these results.
Birefringence control for ion-exchanged channel waveguides at 1.55-um wavelength
Pekka Ayras, Gualtiero Nunzi Conti, Seppo Honkanen, et al.
We show at 1.55 micrometer wavelength that the waveguide birefringence of ion-exchanged channel waveguides in glass can be broadly tuned by a potassium and silver double-ion- exchange. Two different potassium and silver double-ion- exchange processes are used to make surface waveguides with negligible waveguide birefringence. This is of crucial importance in making devices for dense wavelength division multiplexing (DWDM) systems. The dependence of the waveguide birefringence on the channel width is also reported.
Accurate modeling of y-junctions and couplers made by ion-exchange techniques
Gabriella Motta, Guido Perrone, Daniel Pircalaboiu, et al.
The ion exchange in a glass substrate is probably the most widespread and inexpensive technology used to fabricate integrated optical circuits. In this paper we present a detailed modeling of the refractive index profile evolution in the case of closely spaced diffusion windows where the superposition principle for single isolated guides is no longer valid. This is the typical situation occurring in the geometrically simple yet critical case of a Y-junction branching or of a coupler. The model is based on the solution of the nonlinear parabolic differential equation describing the ion diffusion kinetics by a finite difference approach and has been validated experimentally in the planar waveguide case. Examples of device behaviors in case the refractive index profiles are determined using this coupled diffusion window model are given and compared with those obtained when the superposition of single diffusion windows is used.
Materials, Fabrication, and Testing
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ASOC: a manufacturing integrated optics technology
Mehdi Asghari, Emma J.C. Dawnay
ASOCTM technology refers to the fabrication of integrated optics components in silicon-on-insulator material. The technology is based on the formation of single-mode rib waveguides offering excellent properties and numerous advantages for many applications at 1.3 and 1.55 micrometer wavelength. The advantages offered by ASOCTM technology include low-loss, low birefringence waveguides, well established mass production capability, and the availability of both hybrid and monolithic techniques for active element integration. The overall enabling technology lies in the successful development of a set of waveguide-based functional elements that can be assembled into practical integrated optics devices. The most fundamental waveguide elements include straight waveguides, bends, couplers and fiber- waveguide interfaces. Additional elements such as doped structures and waveguide gratings are often required. Discrete lasers and photo-detectors are also incorporated into ASOCTM technology to provide hybrid devices with a wide range of functionality. The technology is currently employed to manufacture devices for a range of applications in telecommunications. These include a single-fiber bi- directional optical transceiver, a DWDM laser and an optical attenuator.
Characterization of the UV-induced refractive index variation in a new photosensitive glass
Daniel Pircalaboiu, Daniel Milanese, Gabriella Motta, et al.
In this paper we present a quantitative characterization of the effects of UV laser beam exposure in a new germanium doped photosensitive glass. Several samples (both bulk ones and containing waveguides) have been exposed under different conditions to UV laser beams produced both by a C frequency doubled Ar-ion laser and by a pulsed excimer laser. The measured characteristics allowed the estimation of photosensitivity properties for each case. We have then evaluated the thermal stability of the induced index variation measuring the samples kept at temperatures varying from 25 to 400 degrees Celsius.
Cerenkov second harmonic generation for full characterization of single-mode planar nonlinear waveguides
A non conventional method is presented for the determination of the refractive-index profile parameters (index change (Delta) n and optical depth d) of single-mode second-order nonlinear planar waveguides, exploiting second harmonic generation in the Cerenkov configuration. The method is based on the dependence of the output angle of the second-harmonic Cerenkov radiation-mode on the propagation constant of the guided-mode at the fundamental frequency; this is in turn related to the refractive-index profile parameters of the waveguide and to the boundary conditions, thus in particular to the waveguide-cover refractive index nc. If two different liquids of known refractive index are placed as the waveguide cover, two different Cerenkov output-angles are obtained that can be expressed as a function of (Delta) n and d by means of two independent equations, thus allowing the determination of both waveguide parameters. It is worth noting that the waveguide parameters at the fundamental frequency, typically in the near infrared, are obtained by means of measurements performed at the second harmonic wavelength, in the visible, with evident advantages in terms of easiness of operation. The experimental results confirm the reliability of the method.
Modeling and Characterization II
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Full-vectorial beam propagation method in anisotropic and inhomogeneous structures
Francesca Castaldo, Giancarlo Abbate, Enrico Santamato
We present a theoretical and numerical model of light beam propagation in anisotropic and inhomogeneous dielectric structures, obtained as an extension of the scalar FFT-BPM. We solve Maxwell's equations in the Generalized Geometric Optics Approximation (GGOA), which neglects the reflected fields. This is a full-vectorial model because it takes into account the polarization effects due both to the anisotropy and to inhomogeneity of the medium. We have implemented a first version of a numerical code exploiting this method. Some preliminary tests are presented.
CAD models for optical integrated circuits using the radiation spectrum method (RSM) with evanescent modes
In this work, we develop CAD models for optical integrated elements using the Radiation Spectrum Method with evanescent modes focusing on elements based on air gaps in semiconductor waveguides. The effect of the evanescent modes in the simulation and modeling is thus considered. For the simulation of photonic band gap optical integrated circuits, the developed models are introduced in a standard microwave simulator. Thus, the optical circuit can be simulated and its performance.
Design of an integrated optical magic T using the multimode interference phenomena
Salwa El-Sabban, Diaa Abdel-Maguid M. Khalil, Isabelle Schanen-Duport, et al.
In this work, we introduce the design of an integrated optical magic-T based on multimode interference phenomena. This new structure gives the sum and the difference of two input optical beams. The theoretical design has been verified using BPM simulation and good performances are obtained. The effects of geometrical variations as well as the overall performances have been investigated.
Refractive index profile reconstruction from near-field measurements: analysis and assessment
Guido Perrone, Gabriella Motta, Daniel Pircalaboiu, et al.
In this paper we present a critical analysis on the refractive index profile reconstruction from near field measurements. We show that the near field information is not sufficient to uniquely determine the proper index parameters if the refractive index shape it is not already known a priori and then we propose a technique to refine the results found from the inversion. Experimental verifications in the case of waveguides made by ion exchange in a glass substrate confirm the results obtained with simulations.
Perturbational estimation of geometry tolerances for rectangular integrated optics devices
Manfred Lohmeyer, Norbert Bahlmann, Oleksandr Zhuromskyy, et al.
Shifting the location of a dielectric boundary in the cross section of an integrated optical waveguide with piecewise constant refractive index profile results in a permittivity perturbation in a layer along the discontinuity line. On the basis of these thin layer perturbations, we discuss perturbational expressions for the derivatives of the propagation constants with respect to geometry parameters, both for fully vectorial, hybrid and for semivectorial approximations to the basic mode fields. The expressions are numerically verified by comparison with rigorously calculated data for a common semiconductor rib waveguide. Applied to a more complex device, the perturbational approach allows to estimate its complete set of tolerances for the geometry parameters including the wavelength, on the basis of a single mode analysis. This is exemplified with a two rib waveguide coupler. By comparison with conventionally computed tolerances we give some assessment for the applicability of the effective perturbational approach.
Sensors
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Integrated semiconductor laser rotation sensor
Peter J. R. Laybourn, Marc Sorel, Guido Giuliani, et al.
Semiconductor ring lasers have been designed and integrated with auxiliary coupled optical circuits to beat together the contra-rotating modes. The Sagnac effect predicts a beat frequency proportional to rotation rate, although no beat frequency has yet been observed. Calculations from theory predict a high lock-in frequency; improvements to the design and fabrication of the devices should reduce the lock-in frequency to a useful level.
Development of integrated optical tracking sensor by planar optics
Hiroyuki Kawano, Tomohiro Sasagawa, Junichi Nishimae, et al.
A compact and light weight optical tracking sensor for a large capacity flexible disk drive is demonstrated. The size of the optical element is no larger than 5.4 mm in length X 3.6 mm in width X 1.2 mm in height and the weight is only 18 mg. The application of the planar optical technique makes it possible to integrate all passive optical elements onto one transparent substrate. These features are useful for high- speed access, easy optical alignment, mass production, and miniaturization. The design and optical characteristics of the optical tracking sensor are described.
Design and fabrication of a fiber Bragg grating temperature sensor
Sundaram K. Ramesh, Kuo Chu Wong
A Bragg Grating Fiber temperature sensor with a grating period of 1550 nm was designed and fabricated. Excellent linearity was observed in the range -60 degrees Celsius to + 150 degrees Celsius between the shift in center wavelength and temperature. The grating was fabricated using a phase mask with its grating profile normal to the fiber axis. The phase mask was placed directly on top of a Corning SMF CPC6 single mode optical fiber and a tunable (365 - 405 nm) Helium Neon UV laser with an output intensity of 3 mW/cm2 was scanned along the mask for one hour. The wavelength of the Fiber Bragg Grating was measured to be 1550.36 nm. Its performance was characterized by monitoring the shift in the Bragg Wavelength as a function of temperature. This is described with a linear equation of the form T equals KL + b, where T represents temperature in Celsius, L is the position of the Bragg Wavelength as measured on an Optical Spectrum Analyzer, K is the experimentally determined thermal expansion coefficient, and b is the wavelength position corresponding to 0 degrees Celsius. For this fiber sensor, T equals 100L(nm) - 155016. It exhibited a shift in center wavelength of 0.01 nm/degrees Celsius change in temperature.
Poster Session
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Steering characteristics of GaInAs/InP MQW comb-type waveguide optical deflector
Ratapon Satrusajang, Yuichi Nitta, Kazuhiko Shimomura
New type optical deflector with graded refractive index region has proposed. For this device, two types structure that are multi electrode type and comb like electrode type have been numerical analyzed using Finite Difference Beam Propagation Method, and have shown the structural dependence on the deflection angle and the deflection efficiency, etc. We fabricated this optical deflector using GaInAs/InP MQW structure, and we confirmed the fundamental optical deflector using GaInAs/InP MQW structure, and we confirmed the fundamental optical deflection and the wavelength dependence of the device.
Integrated optical sensor
Volodymyr S. Ovechko, Andrij M. Dmytruk, Valentyna P. Mygashko
Porous glass (PG) is specific optical component that has excellent optical features and wide surface area simultaneously. It gives possibilities to design integrated devices for Quantum Electronics, Nonlinear Optics and Chemistry. In particular it can be applied as a sensitive element in optical sensors. We have investigated interaction of gas molecules with PG surface. We used near IR spectroscopy, gasdynamics and capillary condensation methods, and atomic force microscope. Molecules adsorbed on PG surface drastically change their optical properties. The main problem of usage PG as a sensor is to incorporate it to measuring scheme. In parallel with experimental investigation we have been simulated the PG-sensor operation with a computer.
Fabrication and characterization of high-speed integrated electro-optic lens and scanner devices
Kevin T. Gahagan, Venkatraman Gopalan, Jeanne M. Robinson, et al.
We demonstrate two high-speed electro-optic devices: an integrated lens/scanner and a variable radius collimating lens stack fabricated on a single crystal of Z-cut LiTaO3. The lens and scanner components consist of lithographically defined domain-inverted regions extending through the thickness of the crystal. A lens power of 0.233 cm-1kV-1, a deflection angle of 12.68 mrad kV-1, and a scan rate of 225 kHz at 375 V were observed. The collimating lens stack is theoretically capable of collimating the output from 2 - 10 micron diameter channel waveguides.
Fabrication of wavefront sensor microlens array and atmospheric turbulence generator for adaptive optics of a telescope
Seiichiro Kitagawa, Yoichi Kotani, Junichi Kubo, et al.
Nalux has developed a unique 3D nanometric fabrication technology in several years. Unlike conventional diamond turning machines that are restricted to symmetric components, this device is capable of cutting any free-form surface which can be specified by a xyz coordinate map. This 3D nanometric fabrication technology includes CAD/CAM, ultra-precision machining using single crystal diamond, and high precise shape evaluation. The capabilities of the technology are demonstrated in this paper. We have succeeded in fabricating two unique optical components used in an adaptive optics system at the Subaru 8.2 m Telescope of National Astronomical Observatory of Japan. The first component is a microlens array that is used in the wavefront curvature sensor. This 37- element array has the individual lens elements distributed in a nonrectangular pie pattern, with very tight tolerances on focal point, focal length, lens shape, and the radius of each lens. The second component is an atmospheric phase plate that generates the atmospheric phase aberrations. This component requires a prescribed random surface yet requires a high degree of smoothness. This component is used to test adaptive optic systems.
Widely tunable resonant cavity enhanced detectors built around photonic crystals
Burak Temelkuran, Ekmel Ozbay
We report a resonant cavity enhanced (RCE) detector built around a three-dimensional photonic band gap crystal. We have demonstrated the resonant cavity enhanced (RCE) effect by placing microwave detectors in defect structures built around dielectric and metallic based photonic crystals. We measured a power enhancement factor of 3450 for planar cavity structures built around dielectric based photonic crystals. The tuning bandwidth of the RCE detector extends from 10.5 to 12.8 GHz. We also demonstrated the RCE effect in cavities built around metallic structures. The power enhancement for the EM wave within these defect structures were measured to be around 190. These measurements show that detectors embedded inside photonic crystals can be used as frequency selective RCE detectors with increased sensitivity and efficiency when compared to conventional detectors.
Sensors
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Sensitivity enhancement of transducers for total internal reflection fluorescence
Albrecht Klotz, C. Barzen, Andreas Brecht, et al.
We have developed, modeled and optimized optical transducers for total internal reflection fluorescence (TIRF). The transducers are part of a compact and rugged immuno-analytical instrument designed for simultaneous detection of up to six analytes in aquatic samples (e.g. atrazine and 2,4-D). Binding inhibition assays, using Cy5.5 labeled antibodies to detect the target analytes, have been carried out. Calibration curves with mid-points of tests below 1 (mu) g/1 and detection limits below 0.1 (mu) g/1 have been achieved. As transducer either ion exchanged integrated optical channel waveguides or planar multimode slab waveguides have been employed. The transducer performance was significantly enhanced by incorporating thin high index films at the waveguide surface and by applying high refractive index solutions in the superstrate. Peak signal enhancement factors of more than ten have been observed and an increase in signal to noise ratio by a factor of more than four have been achieved. Strong polarization dependent effects on the enhancement by high index films have been found both theoretically and experimentally.