Speckle patterns have been widely employed as a method for precisely determining the wavelength of monochromatic light. In order to achieve higher wavelength precision, a variety of optical diffusing waveguides have been investigated with a focus on their wavelength sensitivity. However, it has been a challenge to find a balance among the cost, compactness, precision, and stability of the waveguide. In this work, we designed a compact cylindrical random scattering waveguide (CRSW) as the light diffuser by mixing TiO₂ particles and ultra-violate adhesive. In the CRSW, speckle patterns are generated by input light scattering off TiO₂ particles multiple times. Additionally, a thin layer of upconversion nanoparticles (UCNPs) was sprayed on the end face of CRSW to allow near-infrared (NIR) light to be converted to visible light, breaking the imaging limitations of visible cameras in the NIR range. We, then, further designed a convolution neural network (CNN) to recognize the wavelength of the speckle patterns with excellent robustness and ability to transfer learning. This resulted in the achievement of a high wavelength precision of 20 kHz (∼0.16 fm) at around 1550 nm with a temperature resistance of ±2 °C. Our results demonstrate a low-cost, compact, and simple NIR wavemeter, which is capable of ultra-high wavelength precision and good temperature stability. It has significant value for applications in high-speed and high-precision laser wavelength measurements.

中文翻译：

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核壳 NaErF4@NaYF4 上转换纳米粒子有资格作为可见光 CCD 的 NIR 散斑波长计

散斑图案已被广泛用作精确确定单色光波长的方法。为了实现更高的波长精度，已经研究了各种光漫射波导，重点是它们的波长灵敏度。然而，在波导的成本、紧凑性、精度和稳定性之间找到平衡一直是一个挑战。在这项工作中，我们通过混合 TiO ₂颗粒和紫外线粘合剂设计了一种紧凑的圆柱形随机散射波导（CRSW）作为光漫射器。在 CRSW 中，散斑图案是由 TiO _{2 的}输入光散射产生的粒子多次。此外，在 CRSW 的端面喷涂了一层薄薄的上转换纳米粒子 (UCNPs)，使近红外 (NIR) 光转换为可见光，打破了可见光相机在 NIR 范围内的成像限制。然后，我们进一步设计了一个卷积神经网络 (CNN) 来识别具有出色鲁棒性和迁移学习能力的散斑图案的波长。这导致在大约 1550 nm 处实现了 20 kHz (∼0.16 fm) 的高波长精度，并且具有 ±2 °C 的耐温性。我们的结果证明了一种低成本、紧凑且简单的 NIR 波长计，它具有超高的波长精度和良好的温度稳定性。它在高速和高精度激光波长测量中的应用具有重要价值。