Dönüölçer için Lityum Niyobat Nanofotonik Çip Tasarımı ve Üretimi

Abstract

Gyroscopes are sensors used to measure the displacement of moving systems based on their rotation angles. A specialized type of these sensors, interferometric fiber-optic gyroscopes (IFOGs), are precise optical systems that determine the rotation angle by measuring the phase difference of light propagating within a fiber-optic cable. The ability of IFOGs to perform highly accurate measurements is critical for the effectiveness of inertial navigation systems (INS). Lithium niobate (LiNbO3) based multifunctional integrated optical chips (MIOCs) play a significant role in IFOGs, which are a subsystem of INS.

Due to its exceptional electro-optic properties, LiNbO3 crystals are widely used in telecommunications and IFOG systems. Through the Pockels effect, the phase of light passing through this crystal can be modulated by an applied electric field. The use of LiNbO3 based MIOCs is essential for enabling closed-loop operation in IFOGs, significantly enhancing system sensitivity. In its thin-film form, LiNbO3 allows the development of nanophotonic electro-optic modulators with low driving voltage requirements and small bending radius. This enables the creation of smaller, more power-efficient devices for fiber-optic communication.

This study aimed to design and fabricate nanophotonic gyroscope chips using thin-film LiNbO3. The design, simulation, and fabrication of monolithic and hybrid nanophotonic devices were conducted. Reducing the waveguide dimensions aims to achieve lower modulation voltages and smaller bending radii, ultimately minimizing the device size. Simulation results supported these goals, and the formation of nanophotonic structures was confirmed through optical microscopy and SEM imaging following fabrication processes.

As an alternative to the challenging production process of thin-film LiNbO3 substrates, efforts were made to develop bulk LiNbO3 substrates with stepwise refractive index profiles suitable for nanophotonic device fabrication. For this purpose, annealed proton exchange (APE) was employed to create a stepwise refractive index structure on the substrate surface. Crystal defects at the depth where waveguides form on bulk LiNbO3 substrates were improved through a pre-annealing process. This improvement was applied to standard MIOC fabrication processes, and comprehensive tests revealed enhanced optical transmission in MIOCs produced with pre-annealed substrates. Furthermore, system-level tests of IFOGs demonstrated significant improvement in temperature-induced bias drift performance.