Electro-optic Mode-controlling Devices Based on Lithium Niobate on Insulator

Description

Mode-division multiplexing (MDM), which allows different modes of a few-mode fiber/waveguide to carry different signals, is evolving into a promising technology to expand the transmission capacity of the current single-mode fiber technology. There have been a number of experiments showing the great potential of MDM for various applications, such as long-haul telecommunication, short-distance data transmission (as in data centers), and on-chip optical interconnection. The advancement of the MDM technology depends critically on the development of mode-controlling devices, which play very much the same roles as the counterpart wavelength-controlling devices in current wavelength-division-multiplexing systems. Over the last six or seven years, there have been many demonstrations of passive mode-controlling devices, such as mode converters, mode (de)multiplexers, and mode filters and PI’s team has contributed much to the development of these devices with the polymer waveguide platform. It is envisaged that future MDM systems require not only passive mode-controlling devices but also active mode-controlling devices that can effectively switch and route fiber/waveguide modes. PI’s research team has demonstrated some mode-controlling devices by making use of the large thermo-optic (TO) effect of polymer waveguides, but the switching speeds of TO devices are slow. To increase the switching speed, PI’s research team has explored the electro-optic (EO) effect of lithium niobite (LN) and demonstrated several novel mode-switching devices using bulk LN. However, the waveguide technology based on bulk LN presents significant difficulties in the device design and the driving voltages required are also too high for practical applications. In this project, the PI plans to explore a new waveguide platform based on LN on insulator (LNOI) for the development of EO mode-controlling devices. In particular, two types of devices are studied: mode switches and switchable mode (de)multiplexers (with or without mode conversion), which are basic components in reconfigurable MDM systems. The availability of commercial LNOI wafers in recent years has made possible the development of efficient high-speed EO modulators with a small footprint, which is particularly important for on-chip applications. It is expected that the use of LNOI can significantly lower the driving voltages of the few-mode devices proposed in this project. The outcome of the project will advance not only the MDM technology, but also the LNOI technology. Equipped with extensive research experience in the development of both passive and active mode-controlling devices, PI’s research team has all the capacity to complete this project and deliver the proposed devices.