Nanoparticles made of different materials usually support optical resonances in the visible to near infrared spectral range, such as the localized surface plasmons observed in metallic nanoparticles and the Mie resonances observed in dielectric ones. Such optical resonances, which are important for practical applications, depend strongly on the morphologies of nanoparticles. Laser irradiation is a simple but effective way to modify such optical resonances through the change in the morphology of a nanoparticle. Although laser-induced shaping of metallic nanoparticles has been successfully demonstrated, it remains a big challenge for dielectric nanoparticles due to their larger Young’s modulus and smaller thermal conductivities. Here, we proposed and demonstrated a strategy for realizing controllable shaping of high-index dielectric nanoparticles by exploiting the giant optical force induced by femtosecond laser pulses. It was found that both Si and Ge nanoparticles can be lit up by resonantly exciting the optical resonances with femtosecond laser pulses, leading to the luminescence burst when the laser power exceeds a threshold. In addition, the morphologies of Si and Ge nanoparticles can be modified by utilizing the giant absorption force exerted on them and the reduced Young’s modulus at high temperatures. The shape transformation from sphere to ellipsoid can be realized by laser irradiation, leading to the blueshifts of the optical resonances. It was found that Si and Ge nanoparticles were generally elongated along the direction parallel to the polarization of the laser light. Controllable shaping of Si and Ge can be achieved by deliberately adjusting the excitation wavelength and the laser power. Our findings are helpful for understanding the giant absorption force of femtosecond laser light and are useful for designing nanoscale photonic devices based on shaped high-index nanoparticles.

为了研究微/纳米技术在光学、精密加工和精确定位等领域的应用，提出了一种线性偏摆复合型压电微动平台，以实现线性运动和偏摆运动。对平台的组成和工作原理进行阐述，建立两种运动的数学模型，并进行运动性能仿真。根据拟定的尺寸加工出样机，对样机的运动能力和频响特性进行测试。最后，通过比例积分微分（Proportional Integral Derivative， PID）反馈实现对平台的跟踪控制。仿真和实验结果表明：该平台具有良好的运动精度和解耦性，一阶固有频率可以达到333.8 Hz，能够实现24.924 μm的线性运动和1.330 mrad的角度摆动，实现了微/纳米级别的运动，在精密光学、精确定位等领域具有广阔的应用前景。

在前向光散射颗粒测试技术中，反演算法是影响测量结果的主要因素之一。遗传算法作为一种较新的自适应全局优化算法，其参数优化和目标函数的设计决定了颗粒粒径分布的反演效果。本文对遗传算法中相关参数的设置进行讨论，通过数值模拟验证了该算法对多分散颗粒系统粒径分布的反演效果，并对聚苯乙烯标准颗粒进行实测和反演计算。结果表明：遗传代数为3 200、种群尺度为50、交叉算子0.7、变异算子为0.002和光顺因子权重系数为1.5×10-5的优化遗传算法在颗粒粒径分布反演时具有较好的稳定性和抗噪性能，能够有效重建颗粒粒径分布。

High-resolution frequency-domain spectroscopy (FDS) is set up using a coherent and continuous wave terahertz (THz) emitter and receiver. THz waves are generated and detected by two photomixers with two distributed feedback (DFB) lasers. Atmospheric water vapor with different relative humidity is systematically investigated by the FDS. A high-frequency resolution of ～14 MHz is obtained with the help of Hilbert transformation, leading to a well resolved and distinct transmittance characterization of water vapor. Compared with conventional THz time-domain spectroscopy, the high-resolution continuous wave THz spectrometer is one of the most practical systems in gas-phase molecular sensing, identification, and monitoring.