Photonic inverse design for 3-D structures and optical phase change materials

Abstract

Advances in materials science and photonic device fabrication techniques have provided great potential for making better photonic devices. For example, 3-D photonic structures can be fabricated, and optical phase change materials can been utilized to make non-volatile reconfigurable multi-state optical components. These advances call for better design methods to fully exploit their potential. Traditional photonic design methods are inefficient for exploring the full design space because many physical simulations are required and the physical simulations are very time-consuming. Photonic inverse design methods can explore the full design space more efficiently by using the gradient information at the cost of only two physical simulations per iteration. In this thesis, photonic inverse design algorithms based on the adjoint-variable method have been developed for 3-D structures and optical phase change materials. Ultra-compact waveguide polarization converters with 3-D structures and ultra-compact waveguide switches with optical phase change materials have been designed using such algorithms. Both types of devices have ultra-small footprint and can be designed starting from very simple initial structures. After several hours of optimization, the devices will usually exhibit good performance including low insertion loss and high extinction ratio.