Gain modulation by graphene plasmons in aperiodic lattice lasers

Abstract

Two-dimensional graphene plasmon-based technologies will enable the development of fast, compact and inexpensive active photonic elements because, unlike plasmons in other materials, graphene plasmons can be tuned via the doping level. Such tuning is harnessed within terahertz quantum cascade lasers to reversibly alter their emission. This is achieved in two key steps: First by exciting graphene plasmons within an aperiodic lattice laser and, second, by engineering photon lifetimes, linking graphene's Fermi energy with the round-trip gain. Modal gain and hence laser spectra are highly sensitive to the doping of an integrated, electrically controllable, graphene layer. Demonstration of the integrated graphene plasmon laser principle lays the foundation for a new generation of active, programmable plasmonic metamaterials with major implications across photonics, material sciences and nanotechnology.Among the many intriguing properties of graphene, its plasmonic characteristics are some of the most fascinating and potentially useful [1,2]. Long-lived, tunable intrinsic graphene surface plasmons (SP) have already been demonstrated in a number of experiments [3][4][5][6][7][8][9], including optical modulators [10,11], providing the potential for applications [12,13]. In contrast to the noble metals that are usually used in SP devices [13,14], graphene's Fermi energy, E F , and carrier concentration, n s (and therefore its conductivity and SP mode properties), can be altered, for example by electrical gating and surface doping [3,15,16]. Consequently, the behavior of graphene SP-based structures can be modified in situ, without the need for structural device changes. In particular, graphene's optical and plasmonic properties are tunable in the terahertz (THz) spectral region [3,17], giving rise to the possibility of compact electrically controllable THz optical components [18]. We incorporated graphene into a plasmonic THz laser microcavity to dynamically modulate round-trip modal gain values and therefore laser emission via E F . In this way gated graphene becomes a powerful tool with which to control the fundamental properties of a laser -a tool that is potentially extremely fast and all electrical in nature, with negligible electrical power requirements.The interaction between light and matter can be altered by manipulating the electromagnetic density-of-states (DOS) using a micro resonator [19,20]. By incorporating a photonic lattice or plasmonic structure into a laser, one can control the frequency and amplification of resonant modes and hence manipulate the properties of lasing emission [21][22][23]. Furthermore, by breaking the regularity of these structures it is possible to modulate the photon DOS and hence light-matter interaction at several frequencies simultaneously. This technique was used recently to develop an aperiodic distributed feedback (ADFB) cavity laser with a lattice which is in essence a computergenerated hologram [24,25]. The hologram digitally encodes the Fourier transform of a desired optica...

The ultrafast dynamics and conductivity of photoexcited graphene at different Fermi energies

“…The potential for technological breakthroughs employing graphene is particularly high in the field of optoelectronics, given graphene's promising properties for THz technologies [1][2][3][4][5][6][7], photodetection [8], plasmonics [9][10][11], light harvesting [12], data communication [13][14][15][16][17], ultrafast laser technologies [18][19][20], and more. For all such applications it is of primary importance to accurately understand how photoexcitation and the subsequent ultrafast carrier dynamics occur and affect graphene's conductivity.…”

Strong interaction between graphene layer and Fano resonance in terahertz metamaterials

“…Therefore, a range of graphene-based active applications have been proposed and demonstrated in the mid-infrared and THz regime such as absorbers [19][20][21], biosensors [22,23], filters [24][25][26] and modulators [27,28], which are considered as potential competitors to their electrically controllable metallic counterparts [29,30]. Though the function role of graphene in the active control of SPRs has been extensively investigated, the interaction between graphene and metal-based resonant micro/nanostructures has not been fully understood, which is also technically important since it may provide new opportunities to reveal novel physical mechanisms as well as feed back precursors for the calibration of active control and application development of metal-graphene hybrid micro/nanostructures [31][32][33][34][35][36].…”

Broadband negative refraction of hyperbolic highly squeezed graphene plasmons

“…Realizing negative refraction of highly squeezed polaritons, especially that supported by twodimensional (2D) materials (1)(2)(3)(4)(5)(6), such as graphene plasmon polaritons, is an important step toward the active manipulation of light at the extreme nanoscale (7)(8)(9), and can promise many photonic and optoelectronic applications (10)(11)(12)(13)(14)(15)(16)(17). In 2017, the phenomenon of all-angle negative refraction between highly squeezed isotropic graphene plasmons and hexagonal boron nitride's (BN) phonon polaritons, with their in-plane polaritonic wavelengths squeezed by a factor over 100, is theoretically shown possible in the graphene-BN heterostructures (18).…”