title: Integrated photonic power divider with arbitrary power ratios.
abstract: Integrated optical power splitters are one of the fundamental building blocks in photonic integrated circuits. Conventional multimode interferometer-based power splitters are widely used as they have reasonable footprints and are easy to fabricate. However, it is challenging to realize arbitrary split ratios, especially for multi-outputs. In this Letter, an ultra-compact power splitter with a QR code-like nanostructure is designed by a nonlinear fast search method. The highly functional structure is composed of a number of freely designed square pixels with the size of 120×120  nm which could be either dielectric or air. The light waves are scattered by a number of etched squares with optimized locations, and the scattered waves superimpose at the outputs with the desired power ratio. We demonstrate 1×2 splitters with 1:1, 1:2, and 1:3 split ratios, and a 1×3 splitter with the ratio of 1:2:1. The footprint for all the devices is only 3.6×3.6  μm. Well-controlled split ratios are measured for all the cases. The measured transmission efficiencies of all the splitters are close to 80% over 30 nm wavelength range.
authors.forename: Ke
authors.initials: K
authors.lastname: Xu
authors.forename: Lu
authors.initials: L
authors.lastname: Liu
authors.forename: Xiang
authors.initials: X
authors.lastname: Wen
authors.forename: Wenzhao
authors.initials: W
authors.lastname: Sun
authors.forename: Nan
authors.initials: N
authors.lastname: Zhang
authors.forename: Ningbo
authors.initials: N
authors.lastname: Yi
authors.forename: Shang
authors.initials: S
authors.lastname: Sun
authors.forename: Shumin
authors.initials: S
authors.lastname: Xiao
authors.forename: Qinghai
authors.initials: Q
authors.lastname: Song