A Simple Ni/Si Schottky Junction Wavelength Sensor for Dual-Wavelength Mixed-Light Color Detection

In this study, a self-powered wavelength sensor is developed by integrating two back-to-back Ni/Si Schottky junction photodetectors on a single silicon substrate. This structurally simple sensor achieves dual functionality, namely broadband wavelength discrimination and quantitative mixed-color analysis, without requiring external filters or optical components. Owing to the intrinsic wavelength-dependent absorption of silicon, the two detectors exhibit distinctly different spectral responses. As a result, a monotonic relationship between their photocurrent ratio and the incident wavelength enables broadband wavelength discrimination from 365 to 1080 nm, with a mean absolute error of 4.22 nm. Moreover, by inverting the photoresponse using a parameter matrix, the sensor can quantitatively resolve the intensities of two constituent monochromatic components (540 and 620 nm) with mean absolute percentage errors of 4.24 and 2.84%, respectively, and identify the color of the mixed light. By further integrating backend signal-processing circuitry, the system accomplishes real-time identification of both monochromatic wavelengths and binary mixed-light colors. With its simple architecture, self-powered operation, and high integrability, this device shows strong potential for compact and embedded spectral-sensing applications.