Recently, Prof. Qihuang Gong’s group has experimentally demonstrated a plasmon-induced transparency in a unit-cell structure of an asymmetric T-Shape single slit. This work has been published in the online edition of Nano Letters on April 3, 2012 (Jianjun Chen, Zhi Li, Song Yue, Jinghua Xiao, and Qihuang Gong，Plasmon-Induced Transparency in Asymmetric T-Shape Single Slit，http://pubs.acs.org/doi/abs/10.1021/nl300659v). Dr. Jianjun Chen, the first author of the paper, was doctored at Peking University in July, 2011 and was awarded the Excellent Doctoral Dissertation of Peking University. Now, he is working in Beijing University of Posts and Telecommunications.

Combining the electromagnetically induced transparency (EIT) effect with nano–plasmonic structures would open the possibility to achieve ultra–small functional devices such as sensors and modulators. Most studies on this topic mainly focused on the array metallic structures, which are a little bulk and complicated and is not preferred by highly integrated optics. Recently, using a unit–cell structure, which is much compact and easy to be integrated, the EIT–like transmission spectra were theoretically predicted. However, these unit–cell structures utilized strongly localized guided SPPs as incident waves. This makes the experimental observation of EIT–like optical responses being a challenge. Therefore, realizing the EIT–like optical responses experimentally in ultra–small unit–cell structures with easy fabrication is extremely urgent for highly integrated optics.

By utilizing a dielectric–film–coated asymmetric T–shape single slit, which was a unit–cell structure with the footprint of only about 0.9 μm2, the plasmon–induced transparency was experimentally demonstrated. Because of the symmetry breaking in the unit–cell structure, the scattered lights from the two grooves with slightly detuned widths interfere destructively, leading to the plasmon–induced transparency. Here, the utilization of bulk incident waves may expand the physics of the EIT-like plasmonic resonances. These pronounced features in the structure, such as the increased quality factor, ultracompact size, easy fabrication, and convenient experimental observation, have significant applications in ultra–compact plasmonic devices.

This work was supported by the National Basic Research Program of China (973 project), National Natural Science Foundation of China, and State Key Laboratory for Mesoscopic Physics.