Polarization splitter-rotator on thin film lithium niobate based on multimode interference

Area of Science:

• Photonics
• Integrated Optics
• Materials Science

Background:

• Polarization splitter-rotators (PSRs) are crucial for on-chip polarization manipulation.
• Existing TFLN PSRs require sub-micron gaps, complicating lithography and etching.
• There is a need for simpler fabrication methods for TFLN photonic devices.

Purpose of the Study:

• To demonstrate a novel PSR on TFLN utilizing multimode interference (MMI).
• To achieve mode separation with relaxed fabrication constraints.
• To enable low-cost manufacturing of dual-polarization TFLN photonic devices.

Main Methods:

• Design and fabrication of a PSR on TFLN using MMI principles.
• Utilizing an MMI-based mode demultiplexer for mode division.
• Achieving a minimum feature size of 1.5 µm, compatible with i-line contact aligners.

Main Results:

• Demonstrated a PSR with a minimum feature size of 1.5 µm.
• Achieved a polarization extinction ratio (PER) > 16 dB and insertion loss (IL) < 1.0 dB for TE-polarized light (1530-1578 nm).
• Achieved a PER > 10.0 dB and IL < 2.1 dB for TM-polarized light (1530-1569 nm).

Conclusions:

• The MMI-based PSR on TFLN offers a simplified fabrication process compared to traditional methods.
• The device achieves high performance in terms of PER and IL over a broad wavelength range.
• This technology facilitates the cost-effective production of dual-polarization TFLN-integrated photonic devices.