3D printed THz Plano-Convex Lens
Originated from a Gunn oscillator, the 300GHz Gaussian beam is collimated by a spherical lens and then focused by the 3D printed lens. The intensity distribution of the focused THz beam is measured with a Schottky diode mounted on X-Y-Z translation stages.
As one of the leading technologies in manufacturing, 3D printing, also known as additive manufacturing (AM), is based on additive processes, in which successive layers of material are laid down under computer control. 3D printing can be used to produce jewelry, toys, tools, etc., and it has been widely employed in aerospace manufacturing and engineering design. In recent years, 3D printing has been found particularly useful in research labs due to its ability to make specialized and bespoke geometries.
With the rapid development of Terahertz (THz) sources and detectors, THz waves have been applied in areas like security scanning, non-destruction inspection and communication, etc. Thus the research of optical components operating in THz range is of great importance. However, the traditional methods for THz components fabrication are complicated and time-consuming.
The researchers in THz photonics group from Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, proposed a novel method based on 3D printing, and successfully fabricated a THz plano-convex lens from photosensitive resin. It is reported in Chinese Optics Letters, Vol.13, No.2 (2015).
The measurement results of the focal property agree well with the numerical simulation, revealing that this printed lens could effectively focus THz waves. When tested with THz-TDS system, the printing material exhibits stable refractive index and low absorption coefficient in THz region. With the obvious advantage of being fast and easily fabricated on a low cost, 3D printing technology provides new insight in fabrication of more complex THz optical components.
As a novel technology, 3D printing is developing very quickly, which makes it possible to realize fabrication of THz components with complex geometric features." said Prof. Jinsong Liu from this group.
In the following work, researchers will further investigate the dispersion, reflection and power loss properties of the printed lens. In addition, more complicated components, such as lens arrays and Fresnel lenses will be fabricated，which are useful in THz imaging system.
3D打印的太赫兹透镜
图片说明：耿氏振荡器发射300GHz太赫兹光束，经准直后入射3D打印得到的太赫兹透镜。以三维平移台扫描肖特基二极管，获取通过透镜后太赫兹光束的光强分布。
3D打印技术又称为增材制造技术，已成为了引领未来制造业变革的重要技术之一。与传统的减式制造方法不同，待制作的模型首先被分为若干薄层,然后逐层叠加，最终生成立体实物。这种技术以前主要用于打印珠宝、玩具、工具等，现在已应用在航天制造及工程设计领域，近些年人们还发掘出多种3D打印在科研领域的妙用。
随着太赫兹波产生及探测技术的发展，它已广泛应用于安检、无损检测、通信等领域，太赫兹波段的光学器件研究工作变得愈发重要。然而，透镜等太赫兹器件的传统制作方法复杂并且耗时。
华中科技大学的太赫兹光子学团队提出了一种基于3D打印技术快速制作太赫兹器件的方法，以光敏树脂为原材料成功制作了太赫兹透镜。相关结果发表在Chinese Optics Letters 2015年第2期上。
测试结果表明该透镜能够有效聚焦太赫兹波，实验结果与数值仿真一致。此外，采用太赫兹时域光谱技术测量打印材料，表明该材料在太赫兹波段的折射率值稳定，且吸收率很低。这一3D打印技术制作太赫兹透镜的方法展现了快速及低成本的明显优势。
“3D打印是一种发展迅速的新技术，为制作复杂的太赫兹光学器件提供了可能。” 该研究团队的刘劲松教授说。
在后续的工作中，课题组将进一步表征3D打印透镜的色散、反射、能量损耗等性质，探索利用3D打印技术制作菲涅耳透镜及透镜阵列等复杂器件，并将其应用于太赫兹成像等领域。