  We simulate the performance of a gravitational wave interferometer in the
Dual Recycling (DR) configuration, as will be used for systems like
Advanced-LIGO. Our grid-based simulation program models complex interferometric
detectors with realistic optical deformations (e.g., fine-scale mirror surface
roughness). Broadband and Tuned DR are modeled here; the results are also
applied qualitatively to Resonant Sideband Extraction (RSE). Several beneficial
properties anticipated for DR detectors are investigated: signal response
tuning and narrowbanding, power loss reduction, and the reclamation of lost
power as useful light for signal detection. It is shown that these benefits
would be limited by large scattering losses in large (multi-kilometer) systems.
Furthermore, losses may be resonantly enhanced (particularly for RSE), if the
interferometer's modal resonance conditions are not well chosen. We therefore
make two principal recommendations for DR/RSE interferometers: the DR/RSE
cavity must be modally nondegenerate; and fabricated mirror surfaces and
coatings must be as smooth as is practically feasible.

Astrophysics;Instrumentation and Detectors;Optics