Vivek Krishnamurthy

Theoretical Investigation of Metal Cladding for Nanowire and Cylindrical Micropost Lasers

We investigate the transverse modal properties of cylindrical subwavelength metal-clad nanowire and micropost lasers via rigorous theoretical waveguide analysis, including the effects of finite thickness metal cladding and gain in the core. The results of this analysis show that air-metal surface guided TM01 and some hybrid surface guided modes suffer less loss but are less confined to the core, while core-metal surface guided modes are better confined to the core but suffer greater loss. An increase in the thickness of the metal cladding reduces the loss of the core-metal surface guided modes. The modal gain and confinement of the metal-clad cavity are compared to an unclad cavity.

Model Selection Under Limited Information Using a Value-of-Information-Based Indicator

Designers are continuously challenged by complexity, as well as by the excessive instantiation and execution times of models, particularly in the context of integrated product and materials design. In order to manage these challenges, a systematic strategy for evaluating and selecting models is presented in this paper. The systematic strategy is based on value-of-information for design decision making. It consists of a (i) process performance indicator (PPI) to quantify the impact of model refinement from a decision-centric perspective and (ii) a method involving model evaluation. Using this method, a least complex but valid model is evaluated, and, only if necessary, gradually refined it until the most appropriate one is selected. The systematic approach is particularly well suited for integrated product and materials design, and all other scenarios where the perfect knowledge of the true system behavior and bounds of error are not available throughout the design space. The proposed strategy is applied to the design of photonic crystal waveguides for use in a next-generation optoelectronic communication system. In this paper, it is shown that the systematic strategy based on the PPI is useful for evaluating and selecting models particularly when accuracy of the prediction or the associated error bounds are not know.

Comprehensive theory of plane-wave expansion based eigenmode method for scattering-matrix analysis of photonic structures

A plane-wave-based eigenmode method for scattering-matrix propagation of waves through layered photonic structures is presented. Mode matching using plane-wave-based eigenmode expansion requires a balance between the number of plane waves for the expansion of fields and the number of modes (number of eigensolutions) for mode matching. A matrix-free Fourier operator can handle the increase in the number of plane waves for large structures independently of the number of eigenmodes needed for the scattering-matrix analysis. A convergence analysis of the reflection and transmission of photonic crystal and photonic crystal defect structures as a function of the number of plane waves and the number of eigenmodes is carried out.

Robust and optimum designs of non-linearly tapered slow light couplers

In this work, optimum and robust designs of non-linearly tapered slow light couplers are explored. An optimum design yields a set of design parameters that would result in the best transmission. A robust design yields a set of design parameters that would result in good coupling and low transmission variation in the presence of random fabrication errors. It is shown that the uncertainties in the flat dispersion region affect device transmission more strongly than uncertainties in the linear dispersion region of the coupler. Therefore, moderate-length couplers with relatively longer linear dispersion regions yield more robust performance.

Optical simulation of photonic crystal patterned layer lasers

The dispersion relation of a cavity surrounded by multi-layered photonic crystals is obtained using a fast, accurate and generalized round trip operator. This will assist in the optical design of photonic crystal patterned lasers. A 2D quasi-bandgap was obtained for the lowest order mode of a 1D multi-layered photonic crystal. Although the method is demonstrated for 1D photonic crystal layers, the method is general and can be extended to two dimensional systems.

A Design Exploration Method for Adaptive Design Systems

In this paper, we introduce a design exploration method for adaptive design systems (DEM-ADS), which is proposed to manage the uncertainty in the system design process. The proposed method includes the local regression model and an inverse design procedure derived from the existing Inductive Design Exploration Method (IDEM). To demonstrate the proposed method, the design of a photonic crystal coupler and waveguide containing two subsystem analyses is presented. The result indicates that the proposed method effectively attains solutions that are robust to uncertainty in the system more efficiently than IDEM.© 2009 ASME

Efficient 3D simulation of photonic crystal VCSELs

An efficient modular approach is used to develop components for a 3D simulator for complex semiconductor LED and laser structures. In this approach, only drift transport is simulated in bulk regions, while the active region is simulated with models of varying complexity. The approach is tested using a basic vertical-cavity surface emitting laser (VCSEL) structure, and comparisons are made with experimental data. This approach is advantageous for fast simulation of complex photonic crystal LEDs and VCSELs, for which 2D simulation is inadequate.

Designing Embodiment Design Processes Using a Value-of-Information-Based Approach With Applications for Integrated Product and Materials Design

Designers are continuously challenged to manage complexity in embodiment design processes (EDPs), in the context of integrated product and materials design. In order to manage complexity in design processes, a systematic strategy to embodiment design process generation and selection is presented in this paper. The strategy is based on a value-of-information-based Process Performance Indicator (PPI). The approach is particularly well-suited for integrated product and materials design, and all other scenarios where knowledge of a truthful, i.e., perfect, design process and bounds of error are not available in the entire design space. The proposed strategy is applied to designing embodiment design processes for photonic crystal waveguides in the context of a next-generation optoelectronic communication system. In this paper, it is shown that the proposed strategy based on the Process Performance Indicator is useful for evaluating the performance of embodiment design processes particularly when accuracy of the prediction or the associated error bounds are not known.Copyright

Matrix-free plane wave modal expansion approach for robust design of photonic structures

Fourier operator is used in the vectorial Helmholtzpsilas equation for the calculation of layer modes in a 2D slice of a photonic device. The slice modes are then propagated throughout the device via scattering matrices.