Broadband Absorption Engineering of Hyperbolic Metafilm Patterns

Abstract

Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting. E fficient optical absorbers are highly desired on the microscale where they can play a significant role in preventing crosstalk between optical interconnects on integrated photonic chips. In the thermal spectral region, waste heat is a major energy loss (including thermal radiation loss) in both industrial sectors and our daily life 1 . Particularly, as the density of integrated circuits in portable electronic/optoelectronic devices increases, on-chip thermal management becomes a critical research topic. To recover thermal radiation energy from objects with varying temperature, an efficient ultra-broadband absorber is an indispensable component. However, it is challenging to realize ultra-compact broadband absorber for on-chip optical, thermal and energy applications. In classic microwave electromagnetic (EM) approaches, EM wave absorbers have long been explored and widely utilized for important military applications, such as improving radar performance and providing concealment against others' radar systems 2 . In general, however, EM wave absorbers have been limited by their large, bulky dimensions. In recent years, intensive research efforts have been performed to realize compact/portable perfect metamaterial absorbers 3 . For instance, ideal omnidirectional absorption resonances at microwave, terahertz and mid-near infrared (IR) and visible frequencies have been demonstrated using metamaterial EM absorbers constructed by dielectric thin-films sandwiched by a patterned metal film and a flat metal ground plane 3 . Due to the critical coupling and/or impedance matching mechanism 4,5 , a narrow band of incident light can be efficiently coupled to magnetic resonant modes supported in these patterned metal-dielectric-metal metasurface structures. By tuning the geometric parameters of top metal patterns, the narrow band perfect absorption resonance can be tuned freely 3 . Currently, there is great interest in achieving 'black' on-chip metamaterials exhibiting broadband absorption...

Visible-frequency asymmetric transmission devices incorporating a hyperbolic metamaterial

“…These materials offer an efficient way to manipulate the propagation of light to yield a number of novel and exotic phenomena, such as, negative refraction [19][20][21][22][23] , super-resolution imaging [24][25][26] , enhanced optical absorption 27,28 and spontaneous emission 29,30 . In this work, we leverage a visible-frequency hyperbolic metamaterial to implement a planar device of wavelength-scale thickness able to enforce highly asymmetric, broadband transmission of transverse-magnetic (TM) polarized visible-frequency light under illumination at normal incidence.…”

Ultra-Broadband Super Light Absorber Based on Multi-Sized Tapered Hyperbolic Metamaterial Waveguide Arrays

“…1(a)] is sufficiently small, it can be deemed as a series of uniform air/HMM/air waveguide arrays. In our work, Al is used as the metallic layer rather than Au or Ag, although both of Au and Ag can be used as the metallic layer in the HMM light absorber [28], [30]. This is because that, the largest coupling efficiency can be achieved when Al is chosen with the same frequency region, according to our calculation results (not shown here).…”

“…layer. The dispersion relations of air/HMM/air waveguide array can be retrieved by linking Maxwell's equations and boundary conditions [29], [30] (exp(−ik 2 w)…”

Selective radiative heating of nanostructures using hyperbolic metamaterials

“…HMMs were originally of interest for their potential to project images with resolution below the diffraction limit into the far-field, as proposed theoretically [19,20] and later demonstrated experimentally [21]. For thermal radiation, HMMs have been studied for their potential to enhance near-field heat transfer [22][23][24][25] as well as control the spectral and angular distribution of far-field radiation [26][27][28][29].…”