Metalens enhances photodetector sensing

Short-wave infrared (SWIR) detectors, which capture wavelengths between 1 and 2.5 micrometers, are employed in a wide variety of fields, including optical communication, low-light night vision, and LiDAR. In recent years, the development of smaller and more sensitive detectors has driven a need for more compact, integrated, and high-performance detection systems.

Zhang et al. advanced SWIR detectors by integrating a metalens — a flat optical component made of precise nanostructures — to enhance responsivity.

“This research utilizes a metalens to manipulate the wavefront of light, offering a promising route toward next-generation optoelectronic devices with enhanced sensitivity and higher integration density,” said author Zhen Deng.

The metalens is made of uniform cylindrical nanopillars arranged in outwardly radiating circles. It sits atop a crystalline structure absorption layer on a silicon substrate and focuses light onto the absorption region of a photodiode, making the detector 2.4 times more responsive.

At its focal wavelength, the metalens exhibited low dark current, which is critical for increasing detection sensitivity. The measured intensity distribution of the modified detector matched predictions from simulations and showed insensitivity to light polarization.

While the measured enhancement factor of the metalens was slightly lower than the simulated value, researchers attributed this discrepancy to light loss, light absorption, fabrication imperfections, and possible local saturation.

“Our next steps involve optimizing the metalens design and fabrication process to minimize optical losses,” said Deng. “Building on these results, the most critical next step is to scale this technology from individual pixels to full focal plane arrays. Since the entire manufacturing process is fully compatible with standard focal plane array fabrication, seamless scalability and integration with existing chip-level technologies are expected.”

Source: “Monolithic integration of metalens on III-V photodetector for enhanced sensing,” by Jinyu Zhang, Jiale Liu, Le Qin, Jiaxin Yue, Fanlong Meng, Renjie Wen, Zhongshan Zhang, Yang Jiang, Chunhua Du, Haiqing Jia, Hong Chen, Wenxin Wang, and Zheng Deng, APL Photonics (2025). The article can be accessed at https://doi.org/10.1063/5.0301876 .