Abstract
Graphene on different substrates, such as SiO, h-BN and AlO, has been subjected to oscillatory electric fields to analyse the response of the carriers in order to explore the generation of terahertz radiation by means of high-order harmonic extraction. The properties of the ensemble Monte Carlo simulator employed for such study have allowed us to evaluate the high-order harmonic intensity and the spectral density of velocity fluctuations under different amplitudes of the periodic electric field, proving that strong field conditions are preferable for the established goal. Furthermore, by comparison of both harmonic intensity and noise level, the threshold bandwidth for harmonic extraction has been determined. The results have shown that graphene on h-BN presents the best featuring of the cases under analysis and that in comparison to III–V semiconductors, it is a very good option for high-order harmonic extraction under AC electric fields with large amplitudes.
Highlights
Extraction in Graphene: Monte CarloHigh-order harmonic generation has been proved as an effective way of reaching the THz range for traditional semiconductors [1,2,3] and for two-dimensional materials such as graphene [4,5]
The efficiency of graphene for high-order harmonic generation has already been revealed [4], and tunable resonances characterised by large Qfactors have been observed in the THz regime [13]; on the other hand, we have previously evidenced the potentiality of free-standing graphene, concluding that it is possible to reach the THz range in alike conditions than III–V materials [5]; attending to the actual requirements of the experimental works, it is important to develop these analyses for monolayer graphene on different substrates
The Monte Carlo simulations have been carried out considering an ensemble of carriers (104 super-particles and an extrinsic concentration of 1012 cm−2 ) under the action of an alternating electric field and the consideration of the main scattering mechanisms: Intrinsic optical and acoustic phonons are considered by means of the first-order deformation potential approximation, with the proper parameter fitting so the first-principles calculations in the density functional theory are matched [16]
Summary
High-order harmonic generation has been proved as an effective way of reaching the THz range for traditional semiconductors [1,2,3] and for two-dimensional materials such as graphene [4,5]. The efficiency of graphene for high-order harmonic generation has already been revealed [4], and tunable resonances characterised by large Qfactors have been observed in the THz regime [13]; on the other hand, we have previously evidenced the potentiality of free-standing graphene, concluding that it is possible to reach the THz range in alike conditions than III–V materials [5]; attending to the actual requirements of the experimental works, it is important to develop these analyses for monolayer graphene on different substrates. Ensemble Monte Carlo (MC) simulations [12]
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