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We have measured the surface index change and birefringence in K(+)-Na(+) ion-exchanged waveguides and compared the results with theory. The contribution to the index change caused by the polarizability/volume changes (Deltan(p)) is calculated using two theoretical models which use empirical relations based on the glass composition. In both cases, we encounter large discrepancies between the predicted and measured values which are attributed to the inherent deficiency in the models, which assume free expansion of the glass in calculating the volume changes. Recognizing that the net volume change is much smaller, we accurately measure its value and show that both models can be used to predict Deltan(p) with the same accuracy, provided that the correct volume change is used. We show that the limitation in accuracy is dictated by measurement errors and uncertainties in the values of the ionic radii and polarizabilities. We also present a unique and systematic method for determining the compressive stress generated in the glass resulting from ion exchange.

The general belief that the sphere of equal volume provides a better approximation for the extinction cross section of a nonspherical particle than a sphere of equal surface area at small values of the size parameters is not correct. At some values of x, the equal volume sphere is a better approximation; at others, the equal surface area sphere is better. Details depend on the shape, size, and refractive index. For strongly absorbing particles at xpi, the extinction cross section of an equal volume sphere sigma(EV) provides the lower bound, and sigma(EV)S(N)/S(EV) (where S(N) is the surface area of considered nonspherical particle, and S(EV) is the surface area of equal volume sphere) provides the upper bound on the extinction cross section of an arbitrarily shaped nonspherical particle.

Absorption or extinction measurements at wavelengths of 0.5145 and 10.6 microm lead to determination of the mass concentration of carbonaceous smokes with an accuracy of ~20%. The results do not depend on the details of the particle size distribution or on particulate to void ratio.

It is well known that geometrical or dielectric imperfections in conventional graded-index single-mode fibers depolarize light after a few centimeters. A slight improvement in the polarization performance of these fibers is achieved by introducing noncircularity in the core shape. This is evident from the measurements on borosilicate fibers with dumbbell shaped cores. This result is correlated with Marcatili’s analysis, which shows that changing the core geometry, from square to rectangular, does not appreciably alter the difference in the propagation constants of the two fundamental modes with orthogonal polarizations. Thus, the noncircular geometry and the associated increase in stress-induced birefringence introduced during the manufacturing process alone are not sufficient to improve the polarization performance, and the enhancement of the anisotropic birefringence is necessary to achieve single-polarization fibers.

An asymmetry measure is introduced to characterize thin-film optical waveguides that are asymmetric in refractive index. Together with the usual normalized frequency this allows the plotting of universal charts from which the guide cutoff, the effective guide index, and the effective guide thickness can be determined by the use of simple scaling rules. The minimum value of the effective guide thickness is found to be a simple function of wavelength and the film and substrate indices.

This paper considers a zig-zag wave analysis of three-layered biaxially anisotropic film waveguides with one of the principal axes of the crystal in the direction of propagation in each of the three media and other two parallel and perpendicular to the plane of the film. It provides an exact solution for the cutoff condition and approximate analytical expressions for the propagation constant, both near and far from cutoff. These approximations describe the propagation constant with sufficient accuracy even when the approximate components of the refractive index differ by as much as 10%. Several numerical examples illustrate the usefulness of the approximate relations. Graphical plots for the case of LiNbO(3) film waveguides on LiTaO(3) substrate are included.

It is demonstrated that Er doping increases the photorefractive effect in LiTaO3. Raman and fluorescence spectra are used to establish that the upconverted green emission of Er3+ clusters acts as a gating source, significantly increasing the two-photon photorefractive effect of a monochromatic red or near-infrared pump source.

We have extended the local normal mode approach of Burns and Milton to derive the condition for adiabatic invariance in graded-index channel waveguides. The results show that in spite of the index-grading and 2-D confinement, the inequality describing the adiabatic condition is basically the same as that for step-index slab waveguides. To verify the predictions of the theory, we have fabricated, using ion exchange in glass, a cross coupler with two asymmetric input channel waveguides and two symmetric output guides. The experimental results show equal output power (3.0 +/- 0.1 dB) from the two symmetric guides when either of the two unequal guides is excited, demonstrating excellent agreement with the theory.

Tapered transitions in the ion-exchanged glass waveguide are modeled to predict the index profile, propagation constant, and modal field along the taper. Results are in excellent agreement with the experimental data in Ag(+)-Na(+) exchanged tapers fabricated by a two-step process in BK7 glass.

Dispersion relations for TE modes in a planar exponentially graded-index waveguide with self-focusing nonlinear cover material have been solved numerically. It is shown that the threshold power required to pull the field maximum out of the film region into the cover is lower compared with that for the step-index waveguide and agrees well with the experimental results. Empirical relations to calculate the corresponding minimum film thickness and the minimum threshold power are given for the lowest-order mode.

Planar glass waveguides fabricated by diffusion of silver ions in soda-lime–silicate glass substrates have been characterized by measuring the wavelength dependence of propagation constants of the guided modes. The results are in good agreement with theoretical prediction obtained by an accurate WKB analysis using a complementary error function for the index profile. Cutoff wavelengths of higher-order modes are larger than were predicted by the analysis and are a result of higher attenuation encountered close to the cutoff.

Experimental results indicate that the stress-induced strain birefringence in borosilicate elliptically clad fibers arises from the expansion coefficient mismatch between the borosilicate elliptical cladding and the pure silica outer jacket. This strain birefringence cannot be annealed even after repeated thermal cycling. It is shown that, for a given dopant concentration, the birefringence depends primarily on the cladding ellipticity e and increases linearly with increasing ellipticity and expansion coefficient mismatch.

The diameter and refractive index of micrometer sized spherical dielectric particles are simultaneously deduced using the wavelength dependence of backscattering data from optically levitated particles. The accuracy of the results is set by experimental errors in the determination of the wavelength of backscatter resonance peaks and the ratio of slopes of specified peaks. At present the refractive index and diameter can be deduced with relative errors of 5 x 10(-5). This represents the most accurate determination of absolute size and refractive index yet made by light scattering. A reduction of these errors by an order of magnitude is possible. We assume a priori knowledge of diameter and refractive index with accuracy of 10(-1) and 5 x 10(-3), respectively.

In this paper we describe a concentration cell for the measurement of Ag+ ion concentration useful for fabrication of Ag+ − Na+ exchanged waveguides in glass. The scheme is adaptable to other ion exchanges as well. High measurement accuracy (±2 mV) and assured repeatability are possible by standardizing the reference electrode and experimental conditions. Use of such a cell with appropriate analog signal processing should facilitate on-line concentration control by periodic pumping of the exchanging ion into the molten salt bath.

We report optimization of the processing conditions for fabrication of single-mode Ag(+)-Na(+) ion-exchanged waveguides in a soda-lime glass. The surface-index change, the mobility and diffusion coefficient of Ag(+) have been measured at low melt concentrations and the results used for calculation of the index profile using a new simple numerical method for solving the diffusion equation in a two-step process where the index profile is buried by applying an electric field in the second step. The calculated profile is in agreement with that measured. This correlation allows solution of the Helmholtz equation for given process parameters. Single-mode waveguides with desired mode-field distribution have been designed and fabricated with optimized performance and fiber compatibility at 1.3 microm.

Propagation characteristics of highly elliptical submicron core single-mode fibers have been calculated and compared with the measured beat length, cutoff wavelength of the first higher-order mode, and the far-field intensity distribution. The results show excellent agreement in the case of beat length and only reasonable agreement in the case of cutoff and mode field diameter. These discrepancies are discussed and explained.

Solution-deposited polymer films with continuously adjustable refractive index (1.489-1.563) are made by blending in solution two polymers: polymethyl methacrylate (PMMA) and styrene-acrylonitrile copolymer (SAN). The dependence of index of refraction on composition was found to be linear, indicating the compatibility of the two polymers on a molecular basis. In films ~2 microm thick losses less than 0.2 dB/cm were measured. For thicker films (3.5 microm) an increased scattering loss was observed in high SAN content films.