Integration Of Optical Waveguides Research Articles

End-face scattering loss in integrated-optical waveguides

An experimental technique to determine the end-face scattering loss in electro-optic polymer channel waveguides is presented. The technique combines the cut-back and the optimum end-fire coupling methods. A loss resulting from the scattering was a prominent source of waveguide coupling loss and was strongly dependent on the end-face roughness of the guiding and cladding layers induced by cleaving. With the use of our investigation methods, other losses could also be examined with ease and high reliability.

Highly-sensitive passive integrated optical spiral-shaped waveguide refractometer

A passive integrated optical waveguide refractometer based on bendloss changes in a spiral-shaped channel waveguide is proposed and fabricated in Si3N4/SiO2 technology. The experimentally determined performance and the theoretical predictions, based on a simple model for so-called “whispering gallery modes,” agree very well. The minimum detectable refractive index change was measured to be Δn=1.3×10−5.

A simple angular alignment technique for polarization-maintaining-fiber to integrated-optic waveguide with angled interface

A simple and accurate technique for aligning the fiber birefringence axis of a polarization-maintaining-fiber (PMF) with theprincipal axis of a waveguide has been developed. A section of the PANDA type of PMF near the end is etched to expose the two stress applying parts (SAPs). By directly adjusting the orientation of the SAPs in PMF under a microscope, the angular alignment between birefringence axis of PMF and the principal axis of the waveguide can be made easily without using the polarized light sources and associated polarizer optics. The packaging of 1 × 2 array PMFs in silicon v-groove to LiNbO 3 waveguide with angled interface has been fabricated with a total insertion loss of 5 dB.

Characterization of poly(phenylsilsesquioxane) thin-film planar optical waveguides

Characterization results of thin-film poly(phenylsilsesquioxane) (PPSQ) planar-optical waveguides are presented. Results of absorption spectrum, refractive index, thermal stress effect, and waveguide loss measurements performed on 1-2 /spl mu/m PPSQ films indicate this silicon backbone polymer to be a strong potential candidate for optical waveguide integration within microelectronic systems. PPSQ films are shown to exhibit thermal stability with respect to volume, refractive index, and optical loss for temperatures up to 400/spl deg/C. The first TE mode of PPSQ planar optical waveguides between 1.32 and 1.72 /spl mu/m in thickness fabricated on 5-/spl mu/m HiPOX Si wafers exhibited optical loss of 0.16 dB/cm at 632.8 mn.

Phase compensation of bent silica-glass optical channel waveguide devices by vector-wave mode-matching method

Reduction of the radiation loss is essential for the design of integrated-optic devices involving bent waveguides. For wavelength-selective waveguide devices requiring accurate phase control, the effect of bending-induced phase-constant change becomes even more important. The vector-wave mode-matching method is extended for the analysis of both loss and phase characteristics for general integrated-optic bent channel waveguides. For a typical Mach-Zehnder interferometric filter in silica-glass waveguide, the calculated phase-constant change is used in the waveguide path-length compensation which results in excellent agreement between design and measurement.

Grating couplers for dual-channel thin-film waveguide sensors produced by transmission photolithography

Grating-coupled, thin-film integrated optical waveguide (IOW) structures were fabricated using standard transmission photolithography and employed in a fluoro-affinity assay for the trace detection of analyte. Using a ruled chrome-on-quartz mask with a 0.7 m repeat, gratings of three etch depths—0.6, 0.8, and 1.0 mm—were ion milled into 0.5-mm-thick quartz substrates. Silicon oxynitride (SiON) guiding films (1.5 mm) were deposited on the etched substrates by plasma-enhanced chemical vapor deposition (PECVD). Coupling efficiencies for the first diffracted grating orders into the zero-order IOW-guided modes were evaluated at 632.8 nm. The deepest gratings coupled the most light; however, their efficiency was less than half that of prisms. Binding isotherms for fluorescently labeled avidin (Cy5-Av) binding to a biotinylated bovine serum albumin (BSA) adlayer were generated from both prism- and grating-coupled SiON sensor data. Both techniques discriminated the binding of avidin from a 10215 M solution; however run-to-run (intraassay) and between-sensor (interassay) variability reduced reliability of the measurements.

Grating couplers for dual-channel thin-film waveguide sensors produced by transmission photolithography

Grating-coupled, thin-film integrated optical waveguide (IOW) structures were fabricated using standard transmission photolithography and employed in a fluoro-affinity assay for the trace detection of analyte. Using a ruled chrome-on-quartz mask with a 0.7 m repeat, gratings of three etch depths—0.6, 0.8, and 1.0 mm—were ion milled into 0.5-mm-thick quartz substrates. Silicon oxynitride (SiON) guiding films (1.5 mm) were deposited on the etched substrates by plasma-enhanced chemical vapor deposition (PECVD). Coupling efficiencies for the first diffracted grating orders into the zero-order IOW-guided modes were evaluated at 632.8 nm. The deepest gratings coupled the most light; however, their efficiency was less than half that of prisms. Binding isotherms for fluorescently labeled avidin (Cy5-Av) binding to a biotinylated bovine serum albumin (BSA) adlayer were generated from both prism- and grating-coupled SiON sensor data. Both techniques discriminated the binding of avidin from a 10215 M solution; however run-to-run (intraassay) and between-sensor (interassay) variability reduced reliability of the measurements.

Silica-based optical integrated circuits

Silica-based integrated optical waveguide technology is reviewed. Low loss and manufacturable waveguides are made by chemical vapour, flame hydrolysis and electron beam deposition. Fibre to fibre insertion loss is as low as 0.3 dB for a 6 cm long waveguide. Bragg reflective add-drop filters are made with gratings formed by ultraviolet irradiation. The waveguide grating router has found important application as a multiplexer in dense wavelength multiplexed communications systems. Multiplexers with wide pass bands and stop bands are made with Fourier filters: these filters consist of a chain of alternating couplers and delaying arms. The good performance of waveguide grating routers and Fourier filters is due to the high degree of path delay and coupler control achievable by and processing in this technology.

Silicon-on-insulator (SOI) movable integrated optical waveguide technology

The technology of a new type of optical waveguide, the silicon-on-insulator (SOI) movable integrated optical waveguide, is discussed. The fabrication method based on the surface-micromachining technique and wafer bonding is described. Applications in optical switching and optical scanning probing at the communication wavelength of 1300 nm are demonstrated.

Generalized effective index series solution analysis of waveguide structures with positionally varying refractive index profiles

The use of a generalized series solution technique for analyzing semiconductor integrated-optic waveguide devices is presented. This technique can be employed to obtain TE and TM modes for any slab-waveguide structure with an arbitrary index variation, as long as the square of the index in each layer can be fitted to a polynomial function of position. The method is applied to a slab waveguide with a parabolic index profile, an AlGaAs heterostructure electrooptic phase modulator, heterostructure ridge-waveguide structures with sloped sidewalls, and an InGaAs-AlGaAs graded-index separate-confinement-heterojunction quantum-well structure.

Integrated optical waveguides: refractive-index profile control by temperature and electric-field programming

Ion exchange is often used to manufacture integrated optical waveguides in glasses and crystals. The manufacture of low-loss, compact, integrated optical waveguides can be achieved by varying the processing conditions (the temperature and the electric field) during the ion exchange. We have simulated the formation of waveguides in glass with a molten salt silver ion-exchange technique and have shown that, by simply linearly varying the temperature and electric field during processing of waveguides, one can tailor the refractive-index profiles to produce low-loss parabolic and hyperbolic secant dopant profiles or any other generic dopant profile.

Micromechanical optical switching with voltage control using SOI movable integrated optical waveguides

Optical switching is demonstrated using movable integrated optical waveguides fabricated on silicon-on-insulator substrates. The switching effect is produced by the voltage-controlled micromechanical deflection of the movable waveguides. The dynamic response of the deflection is studied. A contrast ratio of 12 dB of switching is obtained using an applied voltage of less than 10 V. At 20 V, the contrast ratio is about 40 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thermally silver ion exchanged integrated-optic lasers in neodymium-doped silicate glass

Continuous-wave integrated-optic channel waveguide lasers operating near 1.06 μm have been fabricated by thermal silver ion exchange in a commercial neodymium-doped glass. The laser slope efficiency and threshold as a function of waveguide width are measured. The laser output wavelength is also shown to display a dependence on the waveguide width. Optimum laser condition is obtained for waveguide structures with 7.5 μm widths.

Chemical Sensing Using Sol-Gel Derived Planar Waveguides and Indicator Phases

A new optical sensing platform based on a combination of planar waveguiding and sol-gel processing technologies is described. The sensing element consists of two, submicrometer thick glass layers supported on an optically thick glass substrate; both layers were fabricated using a sol-gel coating method. The lower layer is a densified glass that functions as a planar integrated optical waveguide (IOW). The upper layer is an undensified glass of lower index doped with an optical indicator that is immobilized, yet remains sterically accessible to analytes that diffuse into the pore network. Formation of a complex between the analyte and indicator is detected via attenuated total reflection (ATR) of light guided in the IOW. Feasibility was evaluated by constructing IOW-ATR sensors for Pb{sup 2+} and pH, based on immobilized xylenol orange and bromocresol purple, respectively. The response of both sensors was sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries. 48 refs., 8 figs.

Plasma Synthesis of Rare Earth Doped Integrated Optical Waveguides

AbstractWe describe a novel means for the production of optically active planar waveguides. The technique makes use of a low energy plasma deposition. Cathodic-arc-produced metal plasmas are used for the metallic components of the films and gases are added to form compound films. Here we discuss the synthesis of A12-xErxO3 thin films. The erbium concentration (x) can vary from 0 to 100% and the thickness of the film can be from Angstroms to microns. In such material, at high active center concentration (x=l% to 20%), erbium ions give rise to room temperature 1.53μm emission which has minimum loss in silica-based optical fibers. With this technique, multilayer integrated planar waveguide structures can be grown, such as Al2O3/Al2-xErO3/A12O3/Si, for example.

Review of the basic methods for characterizing integrated-optic waveguides

Abstract This article presents a short review of the various methods of characterizing integrated-optic waveguides. It is intended to acquaint researchers, particularly beginners in this field, with the principles of some of the widely used techniques of characterizing one-dimensional (planar) and two-dimensional (such as channel or rib) waueguides.

Integrated optic mode order converting and manipulating structures in strip waveguides

The design and implementation of new integrated optic strip waveguide elements are reported that are capable of conversion between transverse modes and selective coupling and separation of transverse modes. The mode converting element utilisers a periodic serpentine structure to achieve mode conversion, and a novel type of three-guide coupler is used to separate the resulting zeroth and first order modes. Devices were fabricated in a polymer/glass waveguide system for a wavelength of 1.3 μm. 94% conversion was observed in a convertor of length of 1.59 mm, with a loss in the convertor of 1.3 dB. The mode separator performs separation of the first order mode with an efficiency of 60% and a zeroth order mode rejection of greater than 20 dB. It is predicted that improved design should yield near 100% conversion with 0.4 dB loss in the convertor, and separator efficiencies near 100%.

Improved two-dimensional beam-propagation method for three-dimensional integrated-optical waveguide structures having rectangular-core cross sections

An optimized effective index method is combined with a two-dimensional beam-propagation method to form an efficient design tool for integrated-optical waveguide structures with rectangular-core cross sections. The accuracy is evaluated by comparisons with the results from a full three-dimensional beam-propagation method.

Scaling laws for integrated optics waveguides

The accurate design of integrated optical S bends, power splitters, and directional couplers is described through a minimum number of normalized parameters. General design curves showing these normalized parameters for waveguides with a step refractive index profile and a quadratic core cross section are given. Thus a wide variety of integrated optical components may be designed accurately without the use of time-consuming numerical methods.

Surface sensitivity of SiON integrated optical waveguides (IOWs) examined by IOW-attenuated total reflection spectrometry and IOW-Raman spectroscopy

A series of Langmuir-Blodgett (LB) films doped with increasing amounts of lipophilic cyanine dye were deposited at the surface of SiON waveguides. Propagation losses of incoupled laser light were measured photometrically, and then modeled using an attenuated total reflection (ATR) version of the Beer-Lambert law. The SiON waveguides exhibit an experimentally measured surface sensitivity of approximately 0.033 cm −1 propagation loss per 10 12 dyes cm −2 and a detection limit of 8.4 × 10 11 dyes cm −2. However, the experimental surface sensitivity was 0.4 times less than that predicted by ATR theory that did not account for scatter losses and dye aggregation in the LB film. The discrimination of small signals above background was demonstrated by collecting the integrated optical waveguide Raman spectrum of a submonolayer of avidin bound to the SiON waveguide surface through a biotin linker. This spectrum is believed to be the first spontaneous Raman spectrum reported for a protein film bound to a dielectric substrate.