Strasser, Patrick; Stark, Glen; Robin, Franck; Erni, Daniel; Rauscher, K.; Wüest, Robert; Jäckel, Heinz:

Optimization of a 60° waveguide bend in InP-based 2D planar photonic crystals

In: Journal of the Optical Society of America : JOSA, A, Optics, image science, and vision, Jg. 25 (2008) ; Nr. 1, S. 67-73
ISSN: 1084-7529, 0740-3232
Zeitschriftenaufsatz / Fach: Elektrotechnik
We present a novel design for a W1 (one missing row of holes) waveguide 60° bend implemented in a substratetype
InP/ InGaAsP/ InP planar photonic crystal based on a triangular array of air holes. The bend has been
designed to provide high transmission over a large bandwidth. The investigated design improvement relies
only on displacing holes while avoiding changing individual holes diameter in the interest of better process
control (homogenous hole depth). Two-dimensional (2D) finite-element simulations were used to increase the
relative transmission bandwidth from 18% to 40% of the photonic bandgap for unoptimized and optimized 60°
bends, respectively. The 2D results were verified by means of rigorous three-dimensional (3D) finite-difference
time-domain (FDTD) simulations. We show that excellent agreement between 2D and 3D simulations can be
obtained, provided a small effective-index shift of −0.024 (−0.74%) and an imaginary loss parameter (ϵ˝
=0.014) is introduced in the 2D simulations. To demonstrate the applicability of our improved design, the bend
was fabricated and measured using the endfire technique. A bending loss of 3 dB is obtained for the optimized
W1 waveguide bend compared to more than 8 dB in the unoptimized case.