Modelling of a Dielectric Waveguide Mirror with Application to Diode Ring Lasers.

The miniaturization and integration of photonic and optoelectronic devices is a major driving force for advancement in materials growth and processing technology. The developments in these areas have allowed extensive integration of individual components, and a number of integrated circuits have been realized. This dissertation presents the analysis of one of these optical components, namely the dielectric waveguide mirror. This is a comprehensive work dealing with the generalized dielectric mirror with arbitrary structure angle. A plane wave expansion technique for analyzing this component is presented. This is the first such analysis which incorporates the full 2-D distribution of the optical waveguide mode, and proves that this is necessary to obtain accurate results. Both the TE and TM polarizations are examined, and the results include reflection, transmission and farfield characteristics. Noteworthy among these results is the prediction of a crescent shaped farfield distribution, and that, unlike the single plane wave case, unity reflection cannot be attained for angles above the traditional critical angle. The dependence of the mode reflection on mode confinement and non ideal mirror geometry, including mirror tilts and offset, is also evaluated. The results from the analysis are applied to the evaluation of a large angle (high reflectivity) mirror. By examining the threshold characteristics of a semiconductor V-laser, mirror reflectivity of approximately 0.9 is obtained. This is about 94% of the expected value from the the mirror analysis. Triangular ring lasers, with three dielectric mirrors, are also investigated. The analysis method is further validated by the excellent agreement, both qualitatively and quantitatively, between the theoretical and experimental results for these devices. The fabricated lasers operated with TE polarization, however, the analysis reveals that TM polarized emission is possible with the appropriate design. Optimization of the device geometry indicates that a threshold current less than 2mA is achievable. A scattering matrix method for determining the asymmetry of the counter-propagating powers in a ring laser is presented. This is an extension of a previously reported method and is applied to, but not limited to, the case of the triangular ring laser. This analysis reveals that backward coupling asymmetry will produce an asymmetry in the internal power ratio of the counter-propagating waves, but a forward coupling difference of only 0.1% predicts a variation in the ratio of 2-3 orders of magnitude. The ratio also shows a high sensitivity to the phase and amplitude of the scattering matrix elements. One possible application of a ring laser is as a laser gyroscope. A qualitative discussion of the use of a semiconductor ring laser for this application is presented. Although a reduction in sensitivity compared to current laser gyros is expected, the device still possesses some potential for use in the area of rotation sensing.