Conventional grating out-couplers in III-V waveguides typically require lengths of several hundreds of microns to outcouple 50 to 90% of the incident optical power. Enhanced coupling strength (ECS) gratings, which reduce the out-coupler grating length to tens of microns, have a large relative permittivity difference between the materials on either side of the grating boundary along with a high index cover layer. With appropriately chosen permittivity and layer thicknesses, the addition of a cover layer “pulls” the peak of the optical mode towards the grating region, resulting in a significant increase in the grating confinement factor. The resulting ECS out-coupler is short, highly efficient, and can be integrated with other III-V optical components, including horizontal cavity lasers and modulators.
The theoretical dependence of the magnitude and spectral width of the out-coupled power as a function of cover layer thickness, low index material thickness, grating depth, and duty cycle is shown using a Floquet-Bloch analysis for two different ECS grating geometries. The design of a high-speed datacom transmitter with ECS grating reflectors and an ECS grating out-coupler is discussed. The proposed laser with an integrated electro-absorption modulator (Laser-EAM) theoretically provides Pulse Amplitude Modulation 2-Level (PAM-2) data rates in excess of 100Gbps with lower latency, less power consumption, and lower cost than existing commercial devices.
Electrical and Computer Engineering
Gary A. Evans
Electrical, Electronics Engineering
Number of Pages
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License
Dezfuli, Maryam, "Second-Order Enhanced Coupling Strength Grating Out-Couplers for a Monolithic Laser-Electro-Absorption Modulator" (2022). Electrical Engineering Theses and Dissertations. 49.