Broadband lightweight flat lenses for long-wave infrared imaging

We experimentally demonstrate imaging in the long-wave infrared (LWIR) spectral band (8 mu m to 12 mu m) using a single polymer flat lens based upon multilevel diffractive optics. The device thickness is only 10 mu m, and chromatic aberrations are corrected over the entire LWIR band with one surface. Due to the drastic reduction in device thickness, we are able to utilize polymers with absorption in the LWIR, allowing for inexpensive manufacturing via imprint lithography. The weight of our lens is less than 100 times those of comparable refractive lenses. We fabricated and characterized 2 different flat lenses. Even with about 25% absorption losses, experiments show that our flat polymer lenses obtain good imaging with field of view of 35 degrees and angular resolution less than 0.013 degrees. The flat lenses were characterized with 2 different commercial LWIR image sensors. Finally, we show that, by using lossless, higher-refractive-index materials like silicon, focusing efficiencies in excess of 70% can be achieved over the entire LWIR band. Our results firmly establish the potential for lightweight, ultrathin, broadband lenses for high-quality imaging in the LWIR band.

我们通过实验展示了使用基于多级衍射光学的单个聚合物平面透镜在长波红外（LWIR）光谱波段（8微米到12微米）的成像。该器件厚度仅为10微米，并且在整个LWIR波段通过一个表面校正了色差。由于器件厚度大幅减小，我们能够使用在LWIR波段有吸收的聚合物，从而可以通过压印光刻技术进行低成本制造。我们的透镜重量不到类似折射透镜的1/100。我们制造并表征了两种不同的平面透镜。即使存在约25%的吸收损耗，实验表明我们的平面聚合物透镜在35度视场和小于0.013度的角分辨率下能获得良好成像。用两种不同的商用LWIR图像传感器对平面透镜进行了表征。最后，我们表明，通过使用像硅这样无损耗、高折射率的材料，在整个LWIR波段可以实现超过70%的聚焦效率。我们的结果有力地证实了在LWIR波段用于高质量成像的轻质、超薄、宽带透镜的潜力。