Search

A five-channel mode division multiplexed on-chip optical bus is designed and demonstrated on a submicron-thick InP membrane wafer bonded on a Si substrate. Dual-core adiabatic tapers are leveraged for realization of the mode (de)multiplexers. The optimized device shows low excess optical loss of maximum 0.14 dB compared to a reference waveguide and low cross talk of maximum −18.5 dB for all five channels over a broad optical bandwidth of 1510–1600 nm. High fabrication tolerance to width variations is also demonstrated, where a low excess loss of less than 1 dB and a low cross talk of less than −14 dB are maintained in the range of 1530–1585 nm, covering the C-band, when the width varies by up to 50 nm. The demonstrated results show an essential step toward a monolithic photonic layer on top of electronic chips for high-capacity on-chip optical interconnects.

In this Letter, we present a method to prepare a mixed electron-beam resist composed of a positive resist (ZEP520A) and C 60 fullerene. The addition of C 60 to the ZEP resist changes the material properties under electron beam exposure significantly. An improvement in the thermal resistance of the mixed material has been demonstrated by fabricating multimode interference couplers and coupling regions of microring resonators. The fabrication of distributed Bragg reflector structures has shown improvement in terms of pattern definition accuracy with respect to the same structures fabricated with normal ZEP resist. Straight InP membrane waveguides with different lengths have been fabricated using this mixed resist. A decrease of the propagation loss from 6.6 to 3.3¿¿dB/cm has been demonstrated.

Grating couplers are widely used to couple light between photonic integrated circuits and optical fibers. Here, we fabricate and characterize a device based on a buried metal grating. In contrast to dielectric gratings, simulations predict strongly reduced parasitic leakage of light to the substrate and are performance independent of the optical buffer thickness, while using standard fabrication processes with high yield. The gratings show a 3 dB bandwidth of 61 nm and chip-to-fiber coupling efficiency of 54%, which makes them attractive building blocks for on-wafer testing and dense optical interconnects.

Optical true time delay (OTTD) is an attractive way to realize microwave beam steering (MBS) due to its inherent features of broadband, low-loss, and compactness. In this Letter, we propose a novel OTTD approach named cyclic additional optical true time delay (CAO-TTD). It applies additional integer delays of the microwave carrier frequency to achieve spectral filtering but without disturbing the spatial filtering (beam steering). Based on such concept, a broadband MBS scheme for high-capacity wireless communication is proposed, which allows the tuning of both spectral filtering and spatial filtering. The experimental results match well with the theoretical analysis.