Twisted Light-Induced Photocurrent in a Silicon Nanowire Field-Effect Transistor.

Light can possess orbital angular momentum (OAM), in addition to spin angular momentum (SAM), which offers nearly infinite possible values of momentum states, allowing a wider degree of freedom for information processing and communications. The OAM of light induces a selection rule that obeys the law of conservation of angular momentum as it interacts with a material, affecting the material's optical and electrical properties. In this work, silicon nanowire field-effect transistors are subjected to light with OAM, also known as twisted light. Electrical measurements on the devices consequently reveal photocurrent enhancements after incrementing the OAM of the incident light from 0ℏ (fundamental mode) to 5ℏ. Such a phenomenon is attributed to the enhancements of the photogating and the photoconductive effects under the influence of the OAM of light, the underlying mechanism of which is proposed and discussed using energy band diagrams. With these observations, a strategy for controlling photocurrent has been introduced, which can be a realization of the application in the field of optoelectronics technology.

Twisted Light-Enhanced Photovoltaic Effect.

Twisted light carries a defined orbital angular momentum (OAM) that can enhance forbidden transitions in atoms and even semiconductors. Such attributes can possibly lead to enhancements of the material's photogenerated carriers through improved absorption of incident light photons. The interaction of twisted light and photovoltaic material is, thus, worth studying as more efficient photovoltaic cells are essential these days due to the need for reliable and sustainable energy sources. Two-dimensional (2D) MoS2, with its favorable optoelectronic properties, is a good platform to investigate the effects of twisted light on the photon absorption efficiency of the interacting material. This work, therefore, used twisted light as the exciting light source onto a MoS2 photovoltaic device. We observed that while incrementing the incident light's quantized OAM at fixed optical power, there are apparent improvements in the device's open-circuit voltage (VOC) and short-circuit current (ISC), implying enhancements of the photoresponse. We attribute these enhancements to the OAM of light that has facilitated improved optical absorption efficiency in MoS2. This study proposes a way of unlocking the potentials of 2D-MoS2 and envisions the employment of light's OAM for future energy device applications.