[论文解读] Direct Light Orbital Angular Momentum Detection in Mid-Infrared based on Type-II Weyl Semimetal TaIrTe4

Jiawei Lai, Junchao Ma+8 more|arXiv (Cornell University)|Feb 16, 2022

Orbital Angular Momentum in Optics被引用 5

一句话总结

本研究通过基于II型外尔半金属TaIrTe4的光电探测器，首次实现了中红外波段轨道角动量（OAM）的直接检测。通过利用具有定制电极结构的轨道光致电流效应，该器件在光束轴周围产生与OAM模数成正比的电流涡旋，实现了拓扑增强的响应度，并为中红外应用实现了片上OAM敏感型焦平面阵列。

ABSTRACT

The capability of direct photocurrent detection of orbital angular momentum (OAM) of light has recently been realized with topological Weyl semimetal, but limited to near infrared wavelength range. The extension of direct OAM detection to midinfrared, a wavelength range that plays important role in a vast range of applications, such as autonomous driving, night vision and motion detection, is challenging and has not yet been realized. This is because most studies of photocurrent responses are not sensitive to the phase information and the photo response is usually very poor in the mid-infrared. In this study, we designed a photodetector based on Type-II Weyl semimetal tantalum iridium tellurides with designed electrode geometries for direct detection of the topological charge of OAM through orbital photogalvanic effect. Our results indicate helical phase gradient of light can be distinguished by a current winding around the optical beam axis with a magnitude proportional to its quantized OAM mode number. The topological enhanced response at mid-infrared of TaIrTe4 further help overcome the low responsivity issues and finally render the direct orbital angular momentum detection capability in mid-infrared. Our study enables on-chip integrated OAM detection, and thus OAM sensitive focal plane arrays in mid-infrared. Such capability triggers new route to explore applications of light carrying OAM, especially that it can crucially promote the performance of many mid-infrared imaging related applications, such as intricate target recognition and night vision.

研究动机与目标

• 将轨道角动量（OAM）的直接检测从近红外扩展至中红外波段，以满足夜间视觉和运动检测等关键应用的需求。
• 克服中红外光电探测器中常见的光电流响应差和相位不敏感等问题。
• 利用II型外尔半金属的拓扑特性增强光电响应，并实现OAM的直接检测。
• 设计具有工程化电极结构的器件，通过螺旋状电流涡旋实现OAM模数的量化分辨。

提出的方法

• 选用II型外尔半金属TaIrTe4作为活性光电探测材料，因其具有强拓扑响应和增强的中红外吸收特性。
• 设计具有非对称螺旋状电极结构的光电探测器，以产生与OAM模数成正比的定向光电流。
• 采用轨道光致电流效应，即携带OAM的光的螺旋相位梯度在TaIrTe4中诱导出围绕光束轴的手性光电流。
• 通过照射不同OAM模态的光，测量光电流的大小和方向，以确认其具有量化响应和模态分辨能力。
• 利用TaIrTe4的本征拓扑保护特性，增强中红外波段的响应度，克服传统材料中响应度低的难题。

实验结果

研究问题

• RQ1 能否利用拓扑半金属在中红外波段实现轨道角动量（OAM）的直接检测？
• RQ2 携带OAM的光的螺旋相位梯度是否能在TaIrTe4中产生与OAM模数对应的量化、定向光电流？
• RQ3 II型外尔半金属TaIrTe4的拓扑响应是否能够克服中红外光电探测器中常见的低响应度问题？
• RQ4 该器件是否能够通过可测量的电流涡旋实现对不同OAM模数的区分？

主要发现

• 该光电探测器通过围绕光束轴的电流涡旋成功区分了OAM模态，其电流大小与量化OAM模数成正比。
• 该器件在中红外波段表现出显著增强的拓扑光电流响应，其响应度远超传统材料。
• 测得的光电流方向随OAM模态符号的改变而反转，证实了对螺旋相位梯度的手性响应。
• 该研究首次在中红外波段实现了OAM的直接检测，填补了该波段在该类应用中的技术空白。
• 研究成果为中红外成像系统中片上OAM敏感型焦平面阵列的设计提供了可能。