Haiguang Institute has made progress in controlling single-layer graphene to generate reverse photocurrent by circularly polarized laser

Recently, the State Key Laboratory of Intense Field Laser Physics of Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences has made progress in the field of circularly polarized laser controlling single-layer graphene to generate reverse photocurrent. The relevant research results were published in Optics Express under the title of Bidirectional residual current in monolayer graphene under foot cycle laser irradiation.

In recent years, the driving effect of femtosecond ultrafast laser has received extensive attention. Exploring the electron dynamics process of laser solid interaction makes it possible to manipulate physical processes in the sub periodic time scale. Graphene has the properties of weak shielding, high damage threshold and ultrafast optical response. it is a promising new material to realize femtosecond ultrafast laser controlling electron motion.

By numerically solving the time-dependent Schrodinger equation and the semiconductor Bloch equation, researchers studied the photocurrent generated by circularly polarized few period laser driving single-layer graphene. The results show that, for a two period circularly polarized laser, the direction reversal of photocurrent can be achieved at a certain peak laser field strength by selecting the appropriate laser wavelength. The occurrence of direction reversal comes from the interference between optical periods, which can be verified by artificially shortening the pulse width to a single period. In addition, the inversion threshold is proportional to the negative square of the laser wavelength in a wide range, and its slope is related to the ratio of the mass kinetic energy of the electron to the photon energy. This study reflects the nature of electron motion in two-dimensional inverse space, and has certain guiding significance for realizing ultrafast optoelectronic integration applications.

Fig. 1 Photocurrent changes with laser peak field strength, incident wavelength 4 μ m. (a) Pulse width 26fs, (b) Pulse width 13fs

Fig. 2 Relationship between inversion threshold and negative square of wavelength

Source: Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences