Deep‐Ultraviolet Hyperbolic Metacavity Laser

which are environmentally friendly and enable portability and high efficiency. Up to date, great progress has been made on the UVC light-emitting diodes (LEDs) by using active regions of AlGaN multiple quantum wells (MQWs) .[8-14] However, the optical output power of current UVC LEDs drops significantly as the light emission wavelength gets shorter. Those LEDs suffer from poor hole injection efficiency in high-Al-content p-type AlGaN, low internal quantum efficiency (IQE) caused by large-lattice-mismatch heteroepitaxy, and strong quantum-confined Stark effect (QCSE), as well as the absorption by the nontransparent GaN contact layers. [15][16][17] A promising approach that dramatically improves the light output power is electron-beam (e-beam) pumping, especially for the short-wavelength UVC spectral range. [3,[18][19][20][21][22][23][24] This approach allows one to bypass the need for p-type or n-type injection layers and, thus, can largely increase the carrier injection efficiency. This provides a unique advantage over conventional LEDs at UVC range, since the p-type doping for high-Al-content AlGaN is High-output-power electron-beam (e-beam) pumped deep ultraviolet (DUV) light sources, operating at 230-270 nm, are achieved by adjusting the well thickness of binary ultrathin GaN/AlN multiple quantum wells. These structures are fabricated on high-quality thermally annealed AlN templates by metal-organic chemical vapor deposition. Owing to the reduced dislocation density, large electron-hole overlap, and efficient carrier injection by e-beam, the DUV light sources demonstrate high output powers of 24.8, 122.5, and 178.8 mW at central wavelengths of 232, 244, and 267 nm, respectively. Further growth optimization and employing an e-gun with increased beam current lead to a record output power of ≈2.2 W at emission wavelength of ≈260 nm, the key wavelength for water sterilization. This work manifests the practical levels of high-output-power DUV light sources operated by using e-beam pumping method. The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201801763.Solid-state deep ultraviolet (DUV) optoelectronic devices in the spectral range of 200-280 nm, i.e., ultraviolet-C (UVC), have attracted much attention for their wide applications in sterilization, medical treatment, security, solar-blind photodetection, and so on. [1][2][3][4][5][6][7] Currently, Al(Ga)N material system is the most promising candidate for solid-state UVC light sources

mentioning

confidence: 99%

Deep Ultraviolet Light Source from Ultrathin GaN/AlN MQW Structures with Output Power Over 2 Watt

Wang

Rong

Иванов

et al. 2019

“…There have been attempts to realize nanolaser using HMM structures based on the emission enhancement mechanism . The broadband Purcell enhancement and more efficient energy transfer from the surface plasmon to the lasing mode due to the large PDOS and nonlocal effect in HMMs pave ways to manipulate the lasing action.…”

Section: D Bulk Hyperbolic Metamaterialsmentioning

confidence: 99%

“…The broadband Purcell enhancement and more efficient energy transfer from the surface plasmon to the lasing mode due to the large PDOS and nonlocal effect in HMMs pave ways to manipulate the lasing action. Figure f presents a single‐mode deep‐ultraviolet plasmonic laser by using a hyperbolic metacavity on a multiple quantum well (MQW) . In the metacavity array composed of nanorod HMMs, all the excited plasmon oscillations can be coupled into one lasing mode.…”

Section: D Bulk Hyperbolic Metamaterialsmentioning

confidence: 99%

“…Compared with other optical metamaterials, like chiral and split ring resonator–based metamaterials, HMMs have advantages of relative ease of fabrication at optical frequencies, broadband nonresonant and 3D bulk responses, and flexible wavelength tunability. As a result, HMMs have attracted widespread interest and become a good multifunctional platform for many exotic applications, such as optical negative refraction and light beam steering, subdiffraction‐limited imaging and nanolithography, spontaneous and thermal emission engineering, ultrasensitive optical, biological, and chemical sensing, omnidirectional and broadband optical absorption …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hyperbolic Metamaterials and Metasurfaces: Fundamentals and Applications

Huo

Zhang

Liang

et al. 2019

171

107

and their potential applications in various fields, including optical waveguiding, imaging, ultrasensitive optical sensing, and electromagnetic cloaking.Among the different types of optical metamaterials proposed and demonstrated to date, there is one class of highly anisotropic metamaterials which exhibit hyperbolic (or indefinite) dispersions, depending on their effective electric tensors (here, we only consider nonmagnetic media with unit magnetic tensors). Such hyperbolic metamaterials (HMMs) have reached the ultra-anisotropic limit of traditional uniaxial crystal and lead to dramatic changes for the light propagation behaviors. [12][13][14][15][16] Compared with other optical metamaterials, like chiral [17,18] and split ring resonator-based metamaterials, [19,20] HMMs have advantages of relative ease of fabrication at optical frequencies, broadband nonresonant and 3D bulk responses, and flexible wavelength tunability. As a result, HMMs have attracted widespread interest and become a good multifunctional platform for many exotic applications, such as optical negative refraction and light beam steering, [12,[21][22][23][24][25][26][27][28] subdiffraction-limited imaging and nanolithography, [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] spontaneous and thermal emission engineering, [71][72][73][74][75][76][77][78][79][80] ultrasensitive optical, biological, and chemical sensing, [81][82][83][84][85][86][87][88][89] omnidirectional and broadband optical absorption. [90][91][92][93] On the other hand, ultrathin metasurfaces, which comprise a class of planar optical metamaterials with many subwavelength structural units, have attracted much attention due to their ability of locally controlling the phase, amplitude, and polarization of light at the interface between two natural materials. [94][95][96][97] 2D planar metasurfaces have many advantages over bulk metamaterials, including simplifying the fabrication and integration process, reducing energy loss, and being compatible with other photonics devices. In this context, as an efficient surface wave modulation platform, hyperbolic metasurfaces (HMSs) with in-plane hyperbolic dispersions have a potential influence on the development of on-chip planar photonic devices. [95,98] In this review, we first discuss the dispersions and realizations of hyperbolic media. Then, we review the recent achievements of various optical applications based on 3D bulk HMMs and 2D planar HMSs. It should be stressed that, although some application scenarios for 3D HMMs and 2D HMSs are analogous, in fact they are not equal to each other because additional constrains will be introduced on the surface wave as the dimensionality degraded, which is accompanied by fancy in-plane Recent advances in nanofabrication and characterization technologies have spurred many breakthroughs in the field of optical metamaterials and metasurfaces that provide novel ways of manipulating light interaction in a well controllable manner. Among these artificial nanostructured materials, ...

“…Besides the above‐mentioned systems, many other configurations for plasmonic lasers have been demonstrated using cavity modes from surface lattice plasmon mode in metal nanoparticles array, Tamm SPP mode, long‐range SPP mode, random mode to other diverse modes . Also, by operating at NIR region with relatively low metal losses, metal‐cladded 3D‐confined subdiffraction‐limit plasmonic nanolasers have been demonstrated, in which the cladding metals support TM cavity modes and behave more like perfect reflecting mirrors .…”

Section: Experimental Demonstrations Of the Plasmonic Nanolasersmentioning

confidence: 99%

Plasmonic Nanolasers: Pursuing Extreme Lasing Conditions on Nanoscale

Gao

et al. 2019

and techniques have been proposed and/ or developed. Here we focus on a newly emerging area-plasmonic nanolaser that pursuing extremely smaller cavity size in one or more dimensions, and consequently extreme lasing conditions, by using a plasmonic cavity with feature size possibly far below the diffraction limit of light.The miniaturization of a laser can be traced back to the early age of the laser, when compact semiconductor structures were introduced. In particular, the introduction of semiconductors as the gain media in 1962, [11,12] followed by a series of elaborately engineered structures from heterostructure, [13] quantum well, [14] vertical-cavity surface-emitting laser (VCSEL), [15,16] microdisk, [17][18][19] photonic crystal, [20][21][22] quantum dot [23,24] to nanowire (NW) [25][26][27] have made great success in shrinking a laser from bulk scale to wavelength level using reduced cavity sizes. [28] For example, to date, typical commercial edgeemitting quantum well laser diodes have dimensions of several micrometers in width and hundreds of micrometers in length, and a single quantum dot can lase in a photonic crystal cavity with overall dimension of merely 0.7(λ/n) 3 , where λ is the vacuum wavelength and n the refractive index of the dielectric. [29] With optimized geometry and material for cavity design, lower structural dimension is expected. However, in a dielectric cavity with limited refractive index n, the cavity size is intrinsically restricted by optical diffraction limit that sets an ultimate limit λ/2n for both cavity length and mode size in all three dimensions.An effective step to shrink a cavity beyond the diffraction limit is converting light into surface plasmon polaritons (SPPs) in nanostructuralized metals, which is a kind of collective oscillation of quasi free electrons on the interface of a metal and a dielectric. [30] While SPP is featured with ultrahigh optical confinement and ultrafast relaxation process as shown in Figure 1a, [31] it is inevitably accompanied by ultrahigh energy dissipation (i.e., Ohmic loss), leading to a mutual balance between the mode size and the optical loss in either a nanowaveguide or a nanocavity as shown in Figure 1b. [32] For example, the transverse mode area of SPP mode on an Ag nanowire with diameter of 100 nm can be as small as 0.01 µm 2 but also exhibits a propagation loss larger than 200 dB mm −1 . Despite of the high loss coefficient of plasmonic resonance at optical frequency, a properly designed nanoplasmonic cavity coupled with a gain medium is possible to lase with miniature cavity length.Owing to their ultrahigh optical confinement, plasmonic nanolasers with cavity sizes beyond the diffraction limit of light, are attracting increasing attention for pursuing extreme lasing conditions on nanoscale including ultracompact cavity mode, ultrafast lasing modulation, significantly enhanced light-matter interaction, and Purcell effect. In this review, the recent progress on plasmonic nanolasers from both theoretical and experimental aspects is intro...