Conventional chiral metalenses based on helicoidal structures suffer from low energy efficiency and fixed chirality due to the extremely low conversion efficiency of cross-circular polarization in helicity-matched structures. Here, we report on high-efficiency and chirality-reversible metalens imaging using nested dual helical surfaces. The high-efficiency chiral metalenses were implemented by splitting one conventional helical surface into two nested ones with independently controllable parameters. When the relative orientations of the two nested helical surfaces were twisted at certain angles, the conversion efficiency of cross-circular polarization (i.e., the effective polarization component in imaging) could be significantly enhanced by one order of magnitude (from 4.5% to 45%) due to constructive interference of surface plasmonic polaritons between the two nested helical surfaces with a single pitch. Furthermore, the chirality of the metalens could be reversed by manipulating the twist angle even though the helicity of the surface is unchanged. Experimental verifications were performed using two-photon laser direct writing, and chiral imaging in the infrared wavelength range of 3–5 µm was successfully realized via lock-in thermography. This demonstration of the high-efficiency and chirality-reversible metalens provides what we believe is a new method to enhance chiral imaging efficiencies and the design possibilities for practical applications.

中文翻译：

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使用嵌套双螺旋面的干涉增强手性可逆二向色性金属离子成像

由于螺旋匹配结构中的交叉圆极化转换效率极低，传统的基于螺旋结构的手性金属化合物具有较低的能量效率和固定的手性。在这里，我们报道了使用嵌套双螺旋表面的高效且手性可逆的金属成像。通过将一个常规的螺旋表面分成两个嵌套的，具有独立可控参数的表面，可以实现高效的手性金属感。当两个嵌套的螺旋面的相对方向以特定角度扭曲时，交叉圆偏振的转换效率（即成像中的有效偏振分量）可以显着提高一个数量级（从4开始）。5％至45％），这是由于两个嵌套螺旋表面之间的表面等离激元极化子之间的相长干涉形成了单个间距。此外，即使表面的螺旋度不变，也可以通过控制扭转角来反转金属离子的手性。使用双光子激光直接写入进行了实验验证，并且通过锁定热成像技术成功地实现了3–5 µm红外波长范围内的手性成像。高效和手性可逆金属元素的这一演示提供了我们认为是提高手性成像效率和实际应用设计可能性的新方法。即使表面的螺旋度不变，也可以通过控制扭转角来反转金属离子的手性。使用双光子激光直接写入进行了实验验证，并且通过锁定热成像技术成功地实现了3–5 µm红外波长范围内的手性成像。高效和手性可逆金属元素的这一演示提供了我们认为是提高手性成像效率和实际应用设计可能性的新方法。即使表面的螺旋度不变，也可以通过控制扭转角来反转金属离子的手性。使用双光子激光直接写入进行了实验验证，并且通过锁定热成像技术成功地实现了3–5 µm红外波长范围内的手性成像。高效和手性可逆金属元素的这一演示提供了我们认为是提高手性成像效率和实际应用设计可能性的新方法。