An optical micro/nanofiber (MNF) is a quasi-one-dimensional free-standing optical waveguide with a diameter close to or less than the vacuum wavelength of light. Combining the tiny geometry with high-refractive-index contrast between the core and the surrounding, the MNF exhibits favorable optical properties such as tight optical confinement, strong evanescent field, and large-diameter-dependent waveguide dispersion. Meanwhile, as a quasi-one-dimensional structure with extraordinarily high geometric and structural uniformity, the MNF also has low optical loss and high mechanical strength, making it favorable for manipulating light on the micro/nanoscale with high flexibility. Over the past two decades, optical MNFs, typically being operated in single mode, have been emerging as a miniaturized fiber-optic platform for both scientific research and technological applications. In this paper, we aim to provide a comprehensive overview of the representative advances in optical MNFs in recent years. Starting from the basic structures and fabrication techniques of the optical MNFs, we highlight linear and nonlinear optical and mechanical properties of the MNFs. Then, we introduce typical applications of optical MNFs from near-field optics, passive optical components, optical sensors, and optomechanics to fiber lasers and atom optics. Finally, we give a brief summary of the current status of MNF optics and technology, and provide an outlook into future challenges and opportunities.

在轨运行载荷的性能不可避免地出现衰减，场地定标是一些卫星载荷在轨辐射定标主要手段之一，其精度主要取决于地表反射率的准确程度。本文介绍了地表反射率自动观测系统原理和系统组成，并在敦煌辐射校正场实现无人执守自动化、无间断的地表光谱反射率测量，采用标准白板法和辐照度法两种方法同步观测，对两种方法获取的地表反射率数据分别进行了短期和长期稳定性的对比分析，地表反射率可直接溯源至标准白板反射率，减少了定标传递环节。结果表明：标准白板法测量地表反射率短期均值偏差为0.130%，长期测量350~600 nm波段均值偏差为4.996%，600~2 500 nm波段均值偏差为2.104%。标准白板法测量地表反射率合理可行，测量曲线连续、平滑、抖动少，可通过定期清洁标准白板提高测量准确性。辐照度法短期测量与标准白板法具有相近的性能，350~1 900 nm波段均值偏差为0.236%，1 900~2 500 nm波段均值偏差为0.443%。长期测量地表反射率整体漂移小，平均漂移为0.735%，但存在反射率曲线局部噪声大的缺点。可将两种方法相结合，获得更为准确的地表反射率数据。

为了减小对卫星上的空间使用，针对定标特点，本文提出了一种用于积分球光源准直照明的自由曲面反射镜设计方法。采用该方法，能够以小口径的积分球实现大面积的方形均匀辐照度分布。首先，通过点光源模型建立自由曲面离轴反射照明数学模型，然后，通过切比雪夫点离散自由曲面，并求解出满足点光源照明的自由曲面模型，最后，分析积分球的光源特性，通过逐步优化自由曲面能量分布方法完成点光源照明模型到积分球照明模型的转变。通过分析可知，设定照明面积为140 mm×140 mm时，目标面的辐照度非均匀性的不均匀度小于0.02。满足星载定标轻量化，短光路，结构简单的需求。

短相干激光光源在进行高精度的干涉测量时，可以消除被测光学元件前后表面反射形成的杂散光，是低相干干涉仪的理想光源。针对低相干干涉应用对光源的需求，依据速率方程和激光调制特性对射频调制下的短相干半导体激光器光谱特性进行了理论研究。搭建了短相干光源系统，研究了半导体激光器斜率效率 $ \eta $、偏置电流 $ {I_b} $、射频信号频率 $ {f_m} $和幅度 $ {A_m} $对其相干长度的影响。实验结果表明，斜率效率大的半导体激光器更有助于短相干特性的实现，随着调制信号频率和幅值增加，工作在阈值附近的激光器相干长度随之降低，该系统在 $ {I_b} = 1.3{I_{th}} $、 $ {f_m} = {\text{950\;MHz}} $、 $ {A_m} = {\text{19\;dBm}} $的条件下获得了相干长度为90 $ {\text{μm}} $的短相干光源。并成功应用于斐索干涉仪上，获得了对比度 $ K = 0.931\;8 $的清晰干涉图像，与现有短相干光源相比，对比度提高了约51.1%，实现了对平行平板玻璃面形的测量。