Brian R. West

Buried ion-exchanged glass waveguides:burial-depth dependence on waveguide width

A detailed theoretical and experimental study of the depth dependence of buried ion-exchanged waveguides on waveguide width is reported. Modeling, which includes the effect of nonhomogeneous time-dependent electric field distribution, agrees well with our experiments showing that burial depth increases linearly with waveguide width. These results may be used in the proper design of integrated optical circuits that need waveguides of different widths at different sections, such as arrayed waveguide gratings.

Fabrication and comprehensive modeling of ion-exchanged Bragg optical add-drop multiplexers

Optical add-drop multiplexers (OADMs) based on asymmetric Y branches and tilted gratings offer excellent-performance in wavelength-division multiplexed systems. To simplify waveguide fabrication, ion-exchange techniques appear to be an important option in photosensitive glasses. Optimum OADM performance depends on how accurately the waveguide fabrication process and tilted Bragg grating operation are understood and modeled. Results from fabrication and comprehensive modeling are compared for ion-exchange processes that use different angles of the tilted grating. The transmission and reflection spectra for the fabricated and simulated OADMs show excellent agreement. The OADMs performance is evaluated in terms of the measured characteristics of the Y branches and tilted gratings.

MMI devices with weak guiding designed in three dimensions using a genetic algorithm

We discuss the design of weakly guided multimode interference (MMI) devices using a genetic algorithm. For devices exhibiting a nonnegligible vertical waveguide offset, such as those produced using ion exchange in glass, three-dimensional modeling is required to properly evaluate the device performance. A combination of semivectorial finite difference modeling in two transverse dimensions and mode propagation analysis (MPA) in the propagation direction is used to evaluate the merit of each trial design. An example is provided of a 1 x 4 power splitter designed for ion exchange, which shows considerable improvement over that obtained by self-imaging theory.

Ion-exchanged waveguides in glass doped with PbS quantum dots

The lowest-loss (≲1dB∕cm) ion-exchanged waveguides in glass doped with PbS quantum dots are presented. Near-field mode profile and refractive index profile using the refracted near-field technique were measured for these waveguides. We demonstrate that the optical properties of this glass remain unchanged during the ion-exchange process.

Ion-exchanged glass waveguides with low birefringence for a broad range of waveguide widths

Optical communications networks require integrated photonic components with negligible polarization dependence, which typically means that the waveguides must feature very low birefringence. Recent studies have shown that waveguides with low birefringence can be obtained, e.g., by use of silica-on-silicon waveguides or buried ion-exchanged glass waveguides. However, many integrated photonic circuits consist of waveguides with varying widths. Therefore low birefringence is consequently required for waveguides having different widths. This is a difficult task for most waveguide fabrication technologies. We present experimental results on waveguide birefringence for buried silver-sodium ion-exchanged glass waveguides. We show that the waveguide birefringence of the order of 10(-6) for waveguide mask opening widths ranging from 2 to 10 microm can be obtained by postprocessing the sample through annealing at an elevated temperature. The measured values are in agreement with the values calculated with our modeling software for ion-exchanged glass waveguides. This unique feature of ion-exchanged waveguides may be of significant importance in a wide variety of integrated photonic circuits requiring polarization-independent operation.

Quantum dots for fiber laser sources

In this invited paper, we will discuss the use of quantum dots as nonlinear optical elements in fiber laser sources. Furthemore, a review of the fabrication of the first low-loss (< 0.5 dB/cm) ion-exchanged waveguides in a quantum-dot-doped glass will be presented. We will discuss the coupling, propagation, absorption, and scattering losses in these waveguides. The near-field mode profile along with the refractive index profile of these waveguides will be presented. This PbS quantum-dot-doped glass was chosen due to its attractive optical gain and bleaching characteristics at wavelengths throughout the near infrared. This bleaching of the ground-state optical transition has been utilized for passive modelocking of a variety of lasers in the near infrared. In addition, we will discuss some of the potential integrated and fiber optics applications of our quantum-dot-doped waveguides.

Advanced modeling and design of ion-exchanged glass waveguides and devices

Glass waveguide devices fabricated by ion exchange have evolved to the point where conventional assumptions of waveguide symmetry and mutual independence are no longer valid. The modeling of ion-exchanged waveguide devices is far more complicated compared to, e.g., silica on Si waveguide devices. For example, during field-assisted ion exchange processes, the nonhomogeneity of ionic conductivity in the vicinity of the waveguide results in a time-dependent perturbation of the electric field. Previous studies have shown that the depth and vertical symmetry of buried waveguides are affected by the field perturbation. In this work, we describe an advanced modeling tool for guided-wave devices based on ion-exchanged glass waveguides. The effect of field perturbation, due not only to the conductivity profile, but also to the proximity of adjacent waveguides or partial masking during a field-assisted burial are accounted for. A semivectorial finite difference method is then employed to determine the modal properties of the waveguide structures.

Determination of ion exchange parameters by a genetic algorithm

Modeling the process of ion exchange in glass requires accurate knowledge of the self-diffusion coefficients of the incoming and outgoing ions. Furthermore, correlating the concentration profile of the incoming ions to a change in refractive index requires knowledge of the correlation coefficient. We present a method by which these three parameters can be quickly determined experimentally, using a genetic algorithm. Comparison with published data is presented.

Bend loss effects in diffused, buried waveguides

Bend loss effects can be a significant concern in the design and performance of diffused, buried waveguide devices. Since diffused, buried waveguides typically do not have analytical mode solutions, the bend mode must be expressed as an expansion of straight waveguide modes. For the case of buried ion-exchanged waveguides, the bend loss is affected by bend radius, the duration of the ion exchange and burial processes, as well as the size of the mask opening used to create the waveguides and applied field during burial. The bend loss effects for each of these variables are explored under typical fabrication conditions.

Buried ion-exchanged glass waveguides featuring low birefringence with a broad range of waveguide widths

Optical communications networks require integrated photonic components with negligible polarization dependence, which typically means that the waveguides must feature very low birefringence. Recent studies have shown that waveguides with low birefringence can be obtained, e.g., by using silica on Si waveguides and by buried ion-exchanged glass waveguides. However, many integrated photonic circuits consist of waveguides with varying widths. Therefore, low birefringence is consequently required for waveguides having different widths. This is a difficult task for most waveguide fabrication technologies. In this paper we present theoretical and experimental results on waveguide birefringence for buried silver ion-exchanged glass waveguides. We show that the waveguide birefringence is on the order of 10-6 for waveguide mask opening widths ranging from 2 to 9 μm. The measured values are in good agreement with the values calculated with our modeling software for ion-exchanged glass waveguides. This unique feature of ion-exchanged waveguides may be of significant importance in a wide variety of integrated photonic circuits requiring polarization independent operation.