Recently, the emerging lithium niobate on insulator (LNOI) technology has attracted much interest, which provides a unique platform for integration of excellent properties of lithium niobate (LN) for optical processing and light-matter interaction enhancement on a chip. Extensive research has been put forth to demonstrate multi-functional devices on LNOI in the past years. However, the realization of the most desired quasi-phase matching (QPM) schemes in nano LNOI films is still in its infancy , due to difficulty in fabricating stable QPM gratings in LNOI films or waveguide structures in PPLNOI films.

Fig.1. Conceptual diagram of periodically polarized lithium niobate film (PPLNOI) ridge waveguide device

Fig.2. Experimental setup and the ridge waveguide chip

We obtain micrometer thick PPLNOI films by mechanical thinning method. Waveguide structures can be fabricated via optical grade dicing. Then, with moving to a LNOI platform and ridge waveguide configuration, we have developed an on-chip Solc-type device based on PPLNOI ridge waveguide structure. With moving to a LNOI platform and ridge waveguide configuration, an active mode converter with reduced voltage and high speed operation is obtained. We have shown that this scheme is promising for both polarization rotation and wavelength filtering for integrated device application.

This research was published in ” Tingting Ding, Yuanlin Zheng, and Xianfeng Chen, On-chip Solc-type polarization control and wavelength filtering utilizing periodically poled lithium niobate on insulator (PPLNOI) ridge waveguide, J. Lightwave Technol. 37(4), 1296-1300 (2019)”.