Solar spectrum measured by waveguide spectral lens

We demonstrate solar spectrum measurement in the visible-near-infrared region by integrated waveguide spectral lens (WSL). Light through the chip is dispersed and focused on a camera placed at the designed distance without any free-space lens. Commercial polymer materials with low propagation loss near visible region are chosen for wafer-scale fabrication. The solar radiation is coupled to a fiber via a home-made setup and the captured light is transmitted over ~50 m to the lab, where the spectrum is examined by two WSL chips for broadband and fine analysis, respectively. The observed O2 (687.7 nm, 761.9 nm) and H2O (718.4 nm) absorption lines are in good agreement with the results from a commercial optical spectral analyzer and the literature. This experiment proves the feasibility of using planar WSL chips as low-cost and versatile components for the development of compact and portable spectrometer equipment.