Ultracompact computational spectroscopy with a detour-phased planar lens

Compact micro-spectrometers have gained significant attention due to their ease of integration and real-time spectrum measurement capabilities. However, size reduction often compromises performance, particularly in resolution and measurable wavelength range. This work proposes a computational micro-spectrometer based on an ultra-thin (~250 nm) detour-phased graphene oxide planar lens with a sub-millimeter footprint, utilizing a spectral-to-spatial mapping method. The varying intensity pattern along the focal axis of the lens acts as a measurement signal, simplifying the system and enabling real-time spectrum acquisition. Combined with computational retrieval method, an input spectrum is reconstructed with a wavelength interval down to 5 nm, representing a 5-time improvement compared with the result when not using computational method. In an optical compartment of 200 μm by 200 μm by 450 μm from lens profile to the detector surface, the ultracompact spectrometer achieves broad spectrum measurement covering the visible range (420−750 nm) with a wavelength interval of 15 nm. Our compact computational micro-spectrometer paves the way for integration into portable, handheld, and wearable devices, holding promise for diverse real-time applications like in-situ health monitoring (e.g., tracking blood glucose levels), food quality assessment, and portable counterfeit detection.