Alejandro Sánchez-Postigo

arXiv2024

Simultaneous measurement of refraction and absorption with an integrated near-infrared Mach-Zehnder interferometer

Most integrated evanescent-field photonic sensors measure changes in either the real part or the imaginary part of the complex refractive index of the sample, i.e., refraction or absorption. Here we propose and experimentally demonstrate a near-infrared sensor based on a silicon nitride Mach-Zehnder interferometer which provides a direct measurement of the complex refractive index. Our architecture exhibits a high sensitivity, achieving limits of detection below $2\cdot 10^{-6}\,\mathrm{RIU}$ for both the real and imaginary parts of the refractive index. We furthermore show that our sensor can be employed as an integrated dispersion spectrometer.

physics.optics↗

arXiv2019

Mapping the global design space of nanophotonic components using machine learning pattern recognition

Nanophotonics finds ever broadening applications requiring complex component designs with a large number of parameters to be simultaneously optimized. Recent methodologies employing optimization algorithms commonly focus on a single design objective, provide isolated designs, and do not describe how the design parameters influence the device behaviour. Here we propose and demonstrate a machine-learning-based approach to map and characterize the multi-parameter design space of nanophotonic components. Pattern recognition is used to reveal the relationship between an initial sparse set of optimized designs through a significant reduction in the number of characterizing parameters. This defines a design sub-space of lower dimensionality that can be mapped faster by orders of magnitude than the original design space. As a result, multiple performance criteria are clearly visualized, revealing the interplay of the design parameters, highlighting performance and structural limitations, and inspiring new design ideas. This global perspective on high-dimensional design problems represents a major shift in how modern nanophotonic design is approached and provides a powerful tool to explore complexity in next-generation devices.

physics.app-ph↗