High-Linearity Back-Illuminated Position-Sensitive Detector Enabled by Nonlinearity Analysis Methodology for 3-D Wavefront Sensor Integration

Adaptive optics (AO) is essential for correcting wavefront aberrations caused by atmospheric turbulence in ground-based astronomical observations. The increasing aperture size of modern telescopes drives the need for AO systems capable of high-speed, large-field wavefront correction. However, conventional Shack–Hartmann wavefront sensors (SHWFSs) based on charge-coupled device (CCD) or complementary metal–oxide semiconductor (CMOS) detectors face challenges in kilohertz-level operation over wide fields of view. This is primarily due to the limited frame rate and dynamic range. To address these challenges, this study introduces a back-illuminated position-sensitive detector (PSD) array, using a physics-based nonlinearity analysis methodology and 3-D interconnect packaging technology. First, a systematic nonlinearity analysis is conducted to reveal the impact of device structure (P+–P–N${}^{-}$versus P+–N–N${}^{-}\text {)}$on positional accuracy, demonstrating that the P+–P–N${}^{-}$structure significantly suppresses nonlinearity through optimized carrier transport. Second, a TCAD simulation model is established to analyze the formation and suppression strategies of electrical crosstalk in the array, revealing that the P+–P–N${}^{-}$structure also achieves significant crosstalk suppression. The fabricated PSD array achieves a fill factor of 79.6%, 3.6 times higher than conventional surface-illuminated counterparts, enabled by redistribution layer (RDL) and flip-chip packaging. The measured results show that PSD array has a position resolution of$0.5~\mu $m, nonlinearity of 0.75%, response time of$2.39~\mu $s, and interpixel crosstalk below 0.6%. Numerical simulations further validate that the array supports a capture rate of 95.9 kHz and an angular dynamic range of 9.9°, exceeding traditional SHWFS by over an order of magnitude.