Mode-Matching Method in Optical Corrugated Waveguides with Large Rectangular Groove Depth

Tsai, Woo-Hu (1995) Mode-Matching Method in Optical Corrugated Waveguides with Large Rectangular Groove Depth. PhD thesis, University of Glasgow.

Abstract

Corrugated structures have been of great interest and importance in many applications. Recently, aperiodic waveguide gratings have played a significant role in distributed feedback (DFB) lasers and in integrated optical devices. The operating characteristics of such structures (periodic and aperiodic cases) have been investigated and discussed intensively during the past two decades. Most of the studies in this field have been carried out using either approximate analytical techniques or simple numerical methods in the analysis for sinusoidal gratings or other types of gratings with small groove depth (or tooth height), in which the reflection coefficients are very small and the radiation losses can be ignored in the calculation. With the help of the latest lithography and etching techniques, the fabrication of rectangular gratings with large groove depth can be realised for many applications. Deep rectangular gratings contribute high, broad, and flat frequency responses at the centre stopband, and have a compact size suitable for on-line and on-chip implementation. However, simple approximate methods are no longer valid in the analysis because the depth of these gratings is too large. The difficulties in the analysis of such a deep rectangular grating follow from the fact that the method which is used in the analysis not only is required to treat each mode produced by every step-junction of the grating with accuracy but also demands that the algorithm of the method be not too cumbersome when applied to an aperiodic grating with a great number of periods and multiple phase shifts. According to the author's knowledge, such a proper method for deep rectangular aperiodic gratings has still not been fully seen in the literature. In this thesis, a mode-matching procedure and a transfer matrix approach are used and modified to analyse waveguides with rectangular gratings with large groove depth. A systematic investigation has been carried out for several discontinuous structures, including single step discontinuities, double-step discontinuities, periodic gratings, and aperiodic gratings with single and multiple phase shifts. In addition, comparisons of our results and those of existing methods are presented. It is shown that the method proposed in this thesis, having minimal approximation in the formulation and using a simple matrix algorithm, is suitable for the analysis of deep rectangular gratings and also for computer processing. Furthermore, applications of deep linearly chirped grating filters, including dispersion compensation and chirped pulse compression in the femtosecond regime, will be discussed, and very good performances are demonstrated.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: J M Arnold
• Keywords: Electrical engineering
• Date of Award: 1995
• Depositing User: Enlighten Team
• Unique ID: glathesis:1995-74884
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 27 Sep 2019 15:41
• Last Modified: 27 Sep 2019 15:41
• URI: https://theses.gla.ac.uk/id/eprint/74884