Integration of grating couplers with a compact photonic crystal demultiplexer on an InP membrane

Photonic-Crystal Demultiplexer With Improved Crosstalk by Second-Order Cavity Filtering

“…The demultiplexed signal is the intentional leakage of the HOM mode across a thinned barrier of the photonic crystal waveguide [9]- [12], [14], [15]. The simple duplication of the same waveguide after the barrier would not only lead to an extra resonance, but also to the unwanted channeling of power in the fundamental mode (FM) of this second waveguide.…”

“…The basic result of decoupling the higher order mode through a PhC barrier without further management is known to lead to excessive crosstalk [14], [15]. Intuitively, the mechanism is a first-order resonance, individually characterized by a resonance shape whose wings are Lorentzian.…”

“…It was first implemented in the so-called "substrate" option on InP-based systems [10]- [13]. Then, as a result of a common effort within the European project FUNFOX, a membrane InP implementation was successfully demonstrated [14]- [16], together with compact 12 grating couplers to address the chip from out-of-plane fibers. This was a success in the sense that an all-photonic-crystal polarization diversity chip could be demonstrated.…”

“…This was a success in the sense that an all-photonic-crystal polarization diversity chip could be demonstrated. [14]- [16]. The channel spacing was 10 nm.…”

“…As for the technological implementation, we describe it schematically, based on existing similar silicon-on-insulator (SoI) devices realized in the ePIXfab academic foundry silicon facility [8], [18], and on the similar physics of the previous InP membrane realizations [14]- [16]. Finally, the results of selected measurements from an ePIXfab device are given, assessing the improved crosstalk.…”