Frequency-tunable terahertz graphene laser enabled by pseudomagnetic fields in strain-engineered graphene

Abstract

Graphene-based optoelectronic devices have recently attracted much attention for the next-generation electronic-photonic integrated circuits. However, it remains elusive whether it is feasible to create graphene-based lasers at the chip scale, hindering the realization of such a disruptive technology. In this work, we theoretically propose that Landau-quantized graphene enabled by strain-induced pseudomagnetic field can become an excellent gain medium that supports lasing action without requiring an external magnetic field. Tight-binding theory is employed for calculating electronic states in highly strained graphene while analytical and numerical analyses based on many-particle Hamiltonian allow studying detailed microscopic mechanisms of zero-field graphene Landau level laser dynamics. Our proposed laser presents unique features including a convenient, wide-range tuning of output laser frequency enabled by changing the level of strain in graphene gain media. The chip-scale graphene laser may open new possibilities for graphene-based electronic-photonic integrated circuits.

Carrier dynamics and nonlinear photonics in strained graphene with pseudo-magnetic fields

“…In this work, we discuss our latest results on strained graphene that provides a new pathway towards solving the two key above-mentioned problems. First, we show the possibility of creating large energy gaps in graphene, which is evidenced by a significant slow-down of carrier dynamics in the presence of pseudo-Landau levels, as summarized in Figures 1 and 2 [1,2]. Also, we demonstrate the second harmonic generation in monolayer graphene by breaking sublattice symmetry that can induce a strong intrinsic second-order nonlinear susceptibility.…”

Strain-induced pseudo-magnetic fields in graphene for novel optoelectronic applications

“…The creation of pseudo-magnetic fields in strained graphene has emerged as a promising route to allow observing intriguing physical phenomena that would be unattainable with laboratory superconducting magnets. Several theoretical works have proposed the possibility of creating large-area uniform pseudo-magnetic fields by straining monolayer graphene along three crystallographic directions [16], [54], [79], but the experimental realization of such promising devices has rarely been demonstrated.…”

“…And the strain gradient can be increased by inducing a higher maximum strain in the neck region while keeping the center region of strained graphene unchanged [126]. Our unique design also allows straining 2D material in a uniaxially straining plan and pads, and then induced non-uniform strain creates pseudo-magnetic fields [16], [54], [79] that are illustrated by the out-of-plane arrows. The timereversal symmetry is preserved without the application of an external magnetic field, which gives rise to pseudo-magnetic fields of opposite signs in the K and K′ valleys [55]- [57], [60], [61], [78].…”

“…In comparison, monolayer graphene is considered a zero-bandgap semiconductor, which allows an ultra-wide-band absorption window, bringing us large absorption bandwidth [2], [15]. Additionally, graphene has superior electrical properties, such as carrier mobilities of 10 6 cm 2 V −1 s −1 , which is 2-3 orders magnitudes higher than typical semiconductors [16]- [19]. Hence, graphene-based EPICs may combine the advantages of superb optical and electronic properties, potentially changing the communication industry [5].…”

“…However, the spatial area of the induced pseudo-magnetic fields in the nanopillar platform is limited to the nanometer scale. Due to the optical diffraction limit, this nanostructure platform has prevented researchers from harnessing large-scale uniform pseudo-magnetic fields and optoelectronic devices, for example, the creation of Landau level lasers based on pseudomagnetic fields [16].…”