Inverse design of 2D nanophotonics devices: 1xN optical power splitters, negative refractive index medium, and photonic nanojet

Abstract

The interaction of light with nanostructures having variation in the refractive index on the order wavelength or subwavelength generates so many rich physical concepts that cannot be easily observed in the conventional medium. As inverse design methods provide effective optimization of the refractive index distribution that is not possible by conventional methods based on the intuition of researcher, they have been recently used in the design of nanophotonic devices. In this study, 2D integrated photonic devices which split optical power equally and exhibit the negative refraction and photonic nanojet were designed through the objective-first inverse design algorithm. Firstly, the optical power splitters (1×N) separate the optical power of the TE or TM fundamental mode at 1.55 μm wavelength up to the four output waveguides. The output powers are approximately equal (± 3%) and their modes are the same input signal modes. Secondly, the negative refractive index medium is designed in the wavelength range of 1.5-1.6 μm, and incident angle of 45°- 60°. Finally, a beam with full width at half maximum (FWHM) 2λ is performed in the scope of the photonic nanojet. Also, the designed structures are discretized by acceptable performance losses considering the production conditions. As a result, 4-channel optical power splitter, negative refractive index medium, and photonic nanojet are revealed using the objective-first algorithm for the first time to the best of our knowledge.