Applications Overview

Optical waveguides: The Model 2010/M is ideally suited to characterization of materials and processes used in optical waveguide fabrication. The system provides routine display of the mode pattern (reflected intensity vs angle of incidence), effective mode indices, and calculation of thickness and index for step index guides and index gradients for graded index guides. In addition, a loss measurement option, based on the moving fiber approach, is available. This apparatus has been tested on guides with loss down to the 0.1-0.2 db/cm range with good results. A high resolution rotary table (a no-charge option) provides effective index resolution of up to ±.00005. As many as four lasers in addition to the standard 633 nm HeNe can be built into the system for multiple wavelength operation (popular secondary wavelengths include 830, 980, 1310, and 1550 nm) and germanium detectors are available for wavelengths beyond 1100 nm. Alternatively, an external port is available to allow use of the system with user-supplied lasers in the wavelength range 400-1600 nm. Multiple wavelength systems (with secondary lasers either built-in or supplied by the user) incorporate multiple beamlines and beamsplitters to permit rapid (30-second) changeover between wavelengths. A variety of coupling geometries can be accommodated, and stock prisms are available to span the effective index range of 1.30-3.35. For detailed information, please see application notes “Optical Waveguide Characterization.” and ”Waveguide Loss Measurement“.
Index measurement of bulk/substrate materials/liquids: The 2010/M provides rapid (5 second) measurements of the refractive index of glasses, polymers, plastics, garnets and other materials (both rigid and flexible) with a routine resolution of ±0003 (±.00005 with a high resolution rotary table). Bulk materials must be reasonably flat (fine polish or optical flatness not required) or slightly convex. Index measurement range extends from 1.0-3.35 and no matching fluids are required. Liquids are also measurable. For complete information, please see application note “Bulk Material/Thick Film Measurement“.
Surface plasmon (SPR) and waveguide sensors: For biological and sensing applications, the 2010/M is an ideal tool to measure shifts in resonance angles for both SPR and waveguide sensor structures. For further information, please see application note "Characterizing SPR and Waveguide Structures for Sensor Applications".
Characterization of nanomaterials: Because of its ability to resolve extremely small index changes, the Model 2010/M has been used extensively to characterize how the incorporation of nanomaterials changes optical properties and dispersion of materials.
Measuring dispersion: Cauchy fitting software, which allows the calculation of complete index vs wavelength curves from index measurements at three or more wavelengths, is provided on every 2010/M system, and if the wavelength range measured includes three visible lasers, Abbe number is automatically calculated. The Cauchy fitting errors for the Model 2010/M are ~.0005 or less for lower index materials if the wavelength range is limited (for example when the ratio of the shortest to the longest wavelength is <1.75). For higher index materials (for example n >1.8) and wider wavelength ranges (for example, 633 -1550 nm), accuracy of Cauchy fits can degrade significantly. Metricon has also developed even more accurate fitting software which will permit calculation of complete index vs wavelength curves which are as accurate as if index measurements had been made at 1-2 nm wavelength increments over the full wavelength range. The new fits, based on proprietary techniques developed at Metricon, will offer typical fitting error of .00005 or less (3-4 times less than the typical measurement error of ~ .0001 -.0002 provided by the prism coupling technique). This means that index at intermediate wavelengths calculated from these new fits will have essentially the same accuracy as if the index had been directly measured by a laser using the prism coupling technique at that wavelength. For further details on measuring dispersion, see "Spectroscopic Measurements of Index vs Wavelength".

Polymers/polyimides/photoresists: Because, in typical applications, these films are relatively thick and often optically absorbing, prism coupling is unmatched for ease and accuracy. Virtually every stage in the processing of these films (hard or soft bake, optical exposure or polymerization, incorporation of nanomaterials) results in changes to thickness, index and dispersion (index vs wavelength). With its ability to resolve slight index changes, the 2010/M is the ideal tool to monitor film parameters throughout the complex processing of these films. In addition, these films often exhibit significant index/dielectric constant anisotropy, easily measured with the TM option. For further information, please see application note "High Accuracy Measurements of Resists, Polyimides, and Polymers".
Index/birefringence/orientation of film and bulk polymer materials: In-plane and perpendicular plane index for polymer materials, including flexible films, are easily measured by the Model 2010/M without the use of toxic or corrosive index matching fluids. In-plane refractive index can also be measured along any arbitrary in-plane direction by a simple rotation of the sample about the coupling point. Measurement of x, y, and z indices also permits an extremely simple and rapid determination of sample crystallinity and orientation determination is also possible. Indices ranging from 1.0 to 3.35 are easily measured and measurements are free of operator subjectivity. Please see Metricon application note "Measuring Index/Birefringence of Polymer Materials".
dn/dT measurements: Index vs temperature can be measured from room temperature up to 200° C. For further information, please see application note "Measuring Index vs Temperature".
Materials for display technologies: Since the prism coupling technique is easily applied to clear substrates, the 2010/M is well suited to measurements (including birefringence) of films used in the manufacture of LCD’s and other display technologies.
Materials for LEDs: The 2010/M easily measures GaN on sapphire or other transparent substrates at 405 nm, 450 nm, or other wavelengths.
Index measurement of epoxies, gels, and other index matching materials: Since measurements are easily made on bulk samples which can be cast to give “blobs” which either roughly flat or gently convex surfaces, the 2010/M is an ideal system for measuring these materials.
Magnetic thin film head materials: The 2010/M provides straightforward thickness and index measurements of thin and thick alumina, Ta2O5, and other films used in magnetic thin film head manufacture. In addition, the VAMFO option permits high accuracy, non-contact measurements of thickness only for films thicker than approximately two microns. Measurements can be made on ALTIC or other substrates, including metal coated substrates.
Measurement of electro-optic/NLO coefficients: Index changes of samples while a voltage (electrical field) is being applied across the sample are easily measured on the 2010/M system. Prisms with electrically conductive coupling faces can be supplied to serve as the top electrode, avoiding the need to coat samples with ITO or other conductive layers.
Opthalmic, contact/intraocular lenses, and other lenses: Index of the convex surface of opthalmic (eyeglass) lenses or other lenses, as well as the thickness and index of lens coatings, are easily measured. Contact/intraocular lenses are also measurable and a cell to measure index of such lenses while submerged in hydrating solution is available - see application note "Measuring Index of Contact and Intraocular Lenses While Submerged in Hydrating or Other Fluid". Multiple wavelength systems are available for determination of Abbe number.
Thick film measurements: No other film measurement technique comes close to matching the Model 2010/M’s performance in measuring films in the thickness range above two microns. And the Model 2010/M now offers as a standard feature the ability to measure thickness and index of films as thick as 100 microns (250 microns with optional longer wavelength lasers). With the VAMFO option, non-contact thickness measurements are possible on thick films ranging from a minimum of 2 microns up to 300 microns.
Plasma nitride or oxynitride: These films have highly variable refractive index and dispersion (refractive index variation with wavelength) which makes accurate thickness measurement difficult with techniques which rely on spectrophotometry (optical interference vs. wavelength). Moreover, in typical applications, these films are usually thick and often absorbing, factors which can lead to inaccuracies with ellipsometer measurements. The 2010/M provides direct, high accuracy thickness results, fully corrected for index, dispersion, and absorption, and NIST standards for index and NIST-traceable standards for thickness are available. In addition, the high accuracy index result, a sensitive indicator of overall run-to-run film consistency, makes it easy to track variations in the performance of film deposition equipment. Dual-layer films of nitride over oxynitride or oxide and oxynitride over oxide are also measurable (see “Multilayer Films” section below).
Low-k or other interlevel dielectrics: Low-k polymer or dielectric films have highly variable optical properties which make them difficult to measure by spectrophotometer-based techniques. In addition, since interlevel dielectrics are relatively thick, ellipsometer measurements are often difficult. Not only does the 2010/M measure such films with ease, but its ability to measure both in-plane and perpendicular plane index allows determination of dielectric constant anisotropy.
Doped oxides: The 2010/M’s unrivaled refractive index resolution provides a sensitive and quick (20 second) measurement of phosphorus content in doped silicon dioxide immediately after deposition. It is by far the quickest, simplest, and most economical way of monitoring phosphorus concentration on a routine basis, and provides a resolution and accuracy comparable to other popular techniques. For further information, please see application note "Monitoring of Phosphorus and Other Dopant Concentrations in Silicon Dioxide".
Multilayer films: For dual film structures in which the upper film has the higher index (e.g., nitride over oxide, or resist/polyimide over oxide), the 2010/M offers straightforward thickness and index measurements of one or both films. As an example, dual layer dielectrics such as nitride or oxynitride over oxide or oxynitride over oxide (both films deposited in a single deposition run), can easily be measured. For this application, the 2010/M measures thickness and index for both films, provided only that the user supplies a rough starting value for the lower film index. For the case of structures with more than two film layers, if the top film index exceeds the index of the layer immediately below, the top film is measurable. If the second film index exceeds the index of the film immediately beneath, it also is measurable. Finally, thick upper films over relatively thin lower films of higher index are often measurable with some slight loss in thickness accuracy (index accuracy is only minimally affected). For further information, please see application note "Dual Film Measurements".
Films on metals and other semiconductors: The Model 2010/M provides high accuracy measurements of films on high index semiconductor substrates such as GaAs or germanium. Moreover, measurements of films on metallic or metal coated substrates are straightforward and are insensitive to the surface properties of the metal (i.e., smoothness/reflectivity). Thickness limits and performance are virtually indistinguishable from measurements on silicon.