Integrating InP Waveguides: Measuring Processing Stress and Modelling Intersecting Waveguides With Low Crosstalk

Abstract

<p>Two major problems in InP waveguide design were studied. The first of these is the effect of processing induced stress on the mode of an InP/lnGaAsP waveguide. The stress in such a waveguide was measured by the technique of the Degree of Polarization of Photoluminescence. The measured stress map was modeled to quantify the spatial distribution of index change within the waveguide itself. The mode of the single-mode waveguide with the stress effects was calculated using the beam propagation technique. The resultant mode exhibited a double peaking which agreed well with the observed mode of the actual waveguide.</p> <p>The second problem studied was that of crossed waveguides. Crossed waveguides are necessary in optoelectronic integrated circuits due to the multiple light paths and planar nature of the fabrication process. Each arm of these crosses requires good throughput with very little power coupled into the other waveguide. Although this is easy to achieve at large crossing angles, at angles below ≈ 10° a significant fraction of the light may couple into the crossing waveguide.</p> <p>This thesis uses the beam propagation method to characterize the loss and crosstalk. Two modified versions of the X-crossed waveguide structure were developed and have shown crosstalk improvements, at angles below 10°, of greater than 20 dB. These improvements are easy to implement and are important due to the extra design freedom they allow the designers of optoelectronic circuits.</p>