After nearly a decade in the fields of inertial navigation and silicon photonics, I’ve come to regard
silicon photonic gyros (SPGs) as one of the most transformative technologies in precision sensing—packing the performance of fiber optic gyros (FOGs) into a tiny silicon chip, it’s quietly reshaping the boundaries of what’s possible in aerospace, autonomous driving, deep-sea exploration, and other sectors.
For years, traditional FOGs have dominated high-precision application scenarios thanks to the Sagnac effect, which detects rotational motion by measuring the phase difference between counterpropagating light beams. However, they have a fatal flaw for large-scale popularization: bulky designs with discrete optical components and hand-spliced fibers, coupled with high costs, confine them to niche fields such as aerospace and national defense.
Silicon photonics has completely changed this landscape. Leveraging CMOS manufacturing processes, it integrates waveguides, splitters, modulators, and even detectors onto a single silicon substrate—shrinking a desktop-sized system to the size of a fingernail. Some designs can integrate core components onto a 0.2-square-centimeter chip, with a volume only a fraction of that of traditional FOG assemblies.
What fascinates me most is that this miniaturization does not come at the cost of precision—when properly designed, SPGs can match the stability of traditional FOGs while significantly reducing production costs and weight, opening doors to previously unfeasible application scenarios. I still remember a 2024 project collaborating with a deep-sea robotics company, where we replaced their clunky FOG with a prototype SPG built on a silicon nitride waveguide platform.
The effect was remarkable: the SPG reduced the weight of the navigation system by 70%, withstood the extreme pressure of 6,000-meter deep seas, and maintained the sub-degree angular accuracy they required—a breakthrough that traditional optical technology could never achieve.
Of course, SPGs are not without challenges. The biggest problem we face is suppressing polarization loss and coupling loss: silicon waveguides have an extremely small mode field size (about 0.5 micrometers), while standard optical fibers have a mode field size of 9 micrometers. Without careful design using tapered couplers or grating structures, a "funnel effect" will occur, causing light loss.
Temperature sensitivity is another tricky issue—silicon has a strong thermo-optic effect, and small temperature fluctuations can distort phase measurement results, requiring precise temperature control or advanced algorithms for real-time compensation.
Nevertheless, we have made significant progress in heterogeneous integration technology—bonding lithium niobate or indium phosphide to silicon substrates to improve modulator performance, while adopting the "silicon-on-insulator (SOI) + silicon nitride" monolithic integration process to combine low-loss passive devices with high-performance active devices.
Domestic enterprises are also showing strong momentum. Chinese manufacturers such as CETC 14th Research Institute and Chongqing Zixingzhe Technology are expanding the production capacity of SPG chips through 180nm and 130nm silicon photonics processes, gradually narrowing the gap with global leaders and confirming that large-scale mass production is within reach.
Amid the industry boom, a key point is often overlooked: SPGs are not just better-performing FOGs, but an innovation platform. We are developing tri-axis SPG designs, integrating three gyros into a single chip to achieve full 3D motion sensing, and pairing them with AI-driven calibration tools to suppress noise and drift in real time.
For autonomous driving, this means navigation systems can operate independently of GPS, maintaining precise positioning even in scenarios such as tunnels or urban canyons. For the aerospace field, it can provide lighter, more reliable attitude control solutions for satellites and drones.
At the end of the day, SPGs combine two major advantages: the high precision of optical gyros and the scalability of semiconductor manufacturing. Teams that will stand out in this field in the future must not only master the physical principles of the Sagnac effect but also grasp the art of transforming lab-scale designs into robust, cost-controllable chips that can adapt to complex real-world environments. With the breakthrough of remaining technical bottlenecks, I firmly believe SPGs will become the invisible core backbone of all navigation systems pursuing ultimate precision.
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