# Controlling the Minimal Feature Sizes in Adjoint Optimization of Nanophotonic Devices Using B-spline Surfaces

## TL;DR

This paper introduces a level-set method based on B-spline surfaces for adjoint optimization in nanophotonic device design, enabling precise control over minimal feature sizes to improve manufacturability.

## Contribution

It presents a novel B-spline surface-based level-set approach that allows explicit control of feature sizes during the inverse design of nanophotonic devices.

## Key findings

- Controlled feature sizes in device designs
- Successful design of wavelength demultiplexer
- Implementation of neural computing structure

## Abstract

Adjoint optimization is an effective method in the inverse design of nanophotonic devices. In order to ensure the manufacturability, one would like to have control over the minimal feature sizes. Here we propose utilizing a level-set method based on b-spline surfaces in order to control the feature sizes. This approach is first used to design a wavelength demultiplexer. It is also used to implement a nanophotonic structure for artificial neural computing. In both cases, we show that the minimal feature sizes can be easily parameterized and controlled.