Compact and Flexible on-Chip Spectrometer Based on Metalens-Assisted Arrayed Waveguide Grating

To address the trade-off between footprint and spectral performance in on-chip spectrometers, this paper presents a compact and flexible on-chip metalens-assisted arrayed waveguide grating (AWG) spectrometer. By integrating an on-chip metalens within the free propagation region (FPR), significant miniaturization with an FPR size of only 40 μm × 20 μm is achieved while improving functional scalability. Two spectrometers with different arrayed waveguide configurations were designed and fabricated, achieving a free spectral range (FSR) of 28 nm with a resolution of 1.31 nm, and an FSR of 18.8 nm with a resolution of 0.935 nm, respectively. Their operating ranges were 1521.1–1549.1 nm and 1510.5–1529.3 nm, and each device contains 12 channels. This compact on-chip spectrometer holds great promise for miniaturized spectral analysis, and its novel approach of integrating metalens with silicon-based devices opens a new path toward scalable and high-density photonic integrated circuits.