Wave mixing and high harmonic generation at two-color multiphoton excitation in two-dimensional hexagonal nanostructures

Efficient high-harmonic generation in graphene with two-color laser field at orthogonal polarization

“…The HHG with different compositions of the driving laser pulses was addressed also for solid targets and nanostructures considering two distinct regimes. First, if the driving field consists of the fundamental wave and its harmonics [4,24,[49][50][51][52][53][54][55], and second, if one of the involved wave frequencies significantly higher than the other one [2,[56][57][58][59][60][61][62]. Two-color high-order wave mixing research reported so far has mainly been performed for gapped systems.…”

“…For 2D semimetals, two-color highorder wave mixing was considered in Ref. [61] in case when one of the frequencies significantly higher than the other one. In Ref.…”

High harmonic generation in triangular graphene quantum dots

“…In the last decade, there has been a growing interest to extend high harmonic generation (HHG) to twodimensional (2D) crystals and nanostructures, such as semimetallic graphene [1], and semiconductor transition metal dichalcogenidescite [2]. The role of graphene as an effective nonlinear optical material has been discussed in many theoretical [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and experimental [23], [24] studies that consider various extreme nonlinear optical effects, in particular, HHG, which takes place in strong coherent radiation fields in the multiphoton regime at excitation of such nanostructures [25], [26]. On the other hand, apart from the remarkable and unique electronic and optical properties of graphene, the lack of an energy gap as a semimetal greatly limits their applicability, in contrast, for example, to bilayer graphene [27][28][29][30][31][32].…”

High harmonic generation in fullerene molecules

“…The use of molecular systems, clusters, and crystals can significantly increase the harmonic intensity by utilizing multiple excitation channels [15][16][17]. Thus, in the last decade, there has been a growing interest to extend HHG to crystals [18][19][20][21][22][23][24][25][26] and two-dimensional nanostructures, such as semimetallic graphene [27][28][29][30][31][32][33][34][35][36][37][38], semiconductor transition metal dichalcogenides [39,40], and dielectric hexagonal boron nitride [41]. Currently, this is a new growing research field -extreme nonlinear optics of nanostructured materials.…”

“…Then, reaching the harmonic ∼160 which corresponds to the transition of the lowest occupied molecular orbital to the highest unoccupied molecular orbital, the HHG rate is saturated. Note that linear dependence of the cutoff harmonics on the field strength is inherent to HHG via discrete levels [60], or in crystals with linear energy dispersion [22,23,37].…”