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RF MODULE

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Compare these ideal values of the propagation constants with the stress-optical case.<br />

ELEMENT SIZE,<br />

CORE<br />

SUBDOMAIN:<br />

2.5E-7 (STRESS) 2.5E-7 (NO STRESS) DIFFERENCE<br />

EFFECTIVE MODE<br />

INDEX<br />

*1e-4<br />

neff1 1.444873 1.444816 .57<br />

neff2 1.445134 1.444828 3.06<br />

neff3 1.445138 1.44507 .63<br />

neff4 1.445399 1.445096 3.03<br />

neff5 1.450871 1.45082 .51<br />

neff6 1.451135 1.45082 3.16<br />

The difference is significant, which shows that the shift in the effective mode indices<br />

due to the stress-optical effect is indeed resolved.<br />

Visual inspection of the 4 higher eigenmodes indicates that these are probably<br />

degenerate in the ideal case of no thermally induced stresses. Moreover, the higher<br />

eigenmodes have a larger portion of energy leaking into the cladding and buffer, and<br />

are thus more affected than the fundamental modes of the distance to the air and<br />

silicon layers. Because of this leakage, the boundary condition will affect the higher<br />

eigenmodes more than the fundamental mode. Thus a refined analysis of the higher<br />

modes would make it necessary to enlarge the computation domain.<br />

STRESS-OPTICAL EFFECTS IN A SILICA-ON-SILICON WAVEGUIDE | 275

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