Lithium niobate-on-insulator (LNOI) is an emerging photonic
platform
that exhibits favorable material properties (such as low optical loss,
strong nonlinearities, and stability) and enables large-scale integration
with stronger optical confinement, showing promise for future optical
networks, quantum processors, and nonlinear optical systems. However,
while photonics engineering has entered the era of automated “inverse
design” via optimization in recent years, the design of LNOI
integrated photonic devices still mostly relies on intuitive models
and inefficient parameter sweeps, limiting the accessible parameter
space, performance, and functionality. Here, we implement a 3D gradient-based
inverse-design model tailored for topology optimization based on the
LNOI platform, which not only could efficiently search a large parameter
space, but also takes into account practical fabrication constraints,
including minimum feature sizes and etched sidewall angles. We experimentally
demonstrate a spatial-mode multiplexer, a waveguide crossing, and
a compact waveguide bend, all with low insertion losses, tiny footprints,
and excellent agreement between simulation and experimental results.
The devices, together with the design methodology, represent a crucial
step toward the variety of advanced device functionalities needed
in future LNOI photonics and could provide compact and cost-effective
solutions for future optical links, quantum technologies, and nonlinear
optics.
We develop a 3D gradient-based inverse design model specially tailored for the LNOI platform, and experimentally demonstrate a spatial-mode multiplexer, a waveguide crossing and a compact waveguide bend with low loss and crosstalk.
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