Improving polarization detection for optoelectronic devices

Optoelectronic devices could be used to detect polarization and measure the vector components of an optical field. Graphene has many promising properties for high-performance light perception applications, but is not sensitive to polarization. However, graphene may be integrated with photodetectors to enhance their polarization detection capability.

Zhang et al. developed a device by integrating an anisotropic plasmonic cavity with a graphene phototransistor. The new device yields enhanced polarization detection, with improved polarization extinction ratio and responsivity compared to current models.

The geometry of the device holds the key to its polarization detection ability. A layer of graphene is separated from a metal plane with a dielectric spacer and topped with an array of metal stripes. Polarization perpendicular to the stripes intensifies a local field in the vicinity of the graphene, increasing absorption and enabling detection, while polarization parallel to the stripes would filter out the light via reflection.

According to the authors, this unique design enhanced the photo-response of transverse magnetic waves by more than an order of magnitude, while restraining the transverse electric waves. This approach allows for polarization extinction ratio as high as 30, higher than any previously reported values for a two-dimensional material based polarization sensitive photodetector.

While their experiment only tested the effectiveness of the new device in the near-infrared range, the authors believe that their approach can be used to enhance polarization selectivity in two-dimensional materials for other wavelengths. This new approach could enhance many fields of optical metrology, such as target recognition under complex circumstances.

Source: “Enhanced polarization sensitivity by plasmonic-cavity in graphene phototransistors,” by Donghai Zhang, Jing Zhou, Changlong Liu, Shangkun Guo, Jianan Deng, Qingyuan Cai, Zhifeng Li, Yafeng Zhang, Wenqing Zhang, and Xiaoshuang Chen, the Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5109249 .