This thesis explores the various aspects of utilizing topology optimization in designing
nanophotonic devices. Either frequency-domain or time-domain methods
is used in combination with the optimization algorithms, depending on
various aims of the designing problems.
The frequency-domain methods are appropriate for problems where the power
is to be maximized or minimized at a few frequencies, without regards on the
detailed profile of the optical pulse or the need of large amount of frequency
samplings. The design of slow light couplers connecting ridge waveguides and
the photonic crystal waveguides is showcased here. It is demonstrated both
numerically and experimentally that the optimized couplers could improve the
coupling efficiency prominently.
With more focus on the time-domain optimization method, the thesis discusses
extensively the design of pulse-shaping filters, which greatly exploits
the benefits of time-domain methods. Finite-difference time-domain method
is used here as the modeling basis for the inverse problem. Filters based on
both one-dimensional gratings and two-dimensional planar structures are designed
and different issues regarding local minima, black and white design,
minimum lengthscale and flexible pulse delay are addressed to demonstrate
time-domain based topology optimization’s potential in designing complicated
photonic structures with specifications on the time characteristics of pulses.
|Place of Publication||Kgs. Lyngby, Denmark|
|Publisher||Technical University of Denmark|
|Number of pages||105|
|Publication status||Published - 2011|