Polymer lattices as mechanically tunable 3-dimensional photonic crystals operating in the infrared

Abstract

Broadly tunable photonic crystals in the near- to mid-infrared region could find use in spectroscopy, non-invasive medical diagnosis, chemical and biological sensing, and military applications, but so far have not been widely realized. We report the fabrication and characterization of three-dimensional tunable photonic crystals composed of polymer nanolattices with an octahedron unit-cell geometry. These photonic crystals exhibit a strong peak in reflection in the mid-infrared that shifts substantially and reversibly with application of compressive uniaxial strain. A strain of ∼40% results in a 2.2 μm wavelength shift in the pseudo-stop band, from 7.3 μm for the as-fabricated nanolattice to 5.1 μm when strained. We found a linear relationship between the overall compressive strain in the photonic crystal and the resulting stopband shift, with a ∼50 nm blueshift in the reflection peak position per percent increase in strain. These results suggest that architected nanolattices can serve as efficient three-dimensional mechanically tunable photonic crystals, providing a foundation for new opto-mechanical components and devices across infrared and possibly visible frequencies.

Functionalized 3D Architected Materials via Thiol‐Michael Addition and Two‐Photon Lithography

“…[7-9] This architectural versatility renders these 3D polymer structures useful for many technological applications, including drug delivery, [10-12] tissue engineering, [13-15] micro/nano-optics [16-17] and photonics. [18-19] …”

High‐Entropy Alloy (HEA)‐Coated Nanolattice Structures and Their Mechanical Properties

“…This includes high strength and fracture toughness, low density, as well as high surface area to volume ratio deduced from the synergistic coupling effect between the geometrical structure and functional constituent materials. [1][2][3][4][5][6][7][8][9] The strength of lattices is determined not only by the order and periodicity of its structure, but also by the constituent materials. [10,11] Recently, numerous engineering materials such as Al 2 O 3, [12][13][14] Ni-P alloy, [4,15] glassy carbon, [16] copper, [17] gold, [18] and metallic glass [19,20] have been employed as constituent materials to significantly enhance the mechanical properties of pristine polymer scaffolds with respect to its strength and stiffness.…”

Designing core-shell 3D photonic crystal lattices for negative refraction

“…We also used PWEM to calculate band structure and EFCs to quantify the effect of modified dielectric constant on AANR frequency when core-shell structures are explored. For this analysis, lattice periodicity remains at a = 4 µm, the total beam diameter is set to b = 0.25a = 1 µm (f = 0.23), and the relative ratio of low-index (n = 1.49) acrylate polymer core material 12 , and high-index (n = 4.0047) Ge shell material 10 is varied by progressively increasing the core diameter and simultaneously shrinking the thickness of the shell to maintain the same total beam diameter. We varied the core diameter from bcore = 0.1b = 100 nm, where shell thickness tshell = (b -bcore)/2 = 450 nm, to bcore = 0.9b = 900 nm, with tshell = (b -bcore)/2 = 50 nm, and in so doing decreased the compound index of the lattice (see Table 2).…”

“…Amorphous carbon is lossy in the mid-infrared (the extinction coefficient κ = 1.8818 at λ = 8.0 µm) but has a higher refractive index of n = 2.9622 at λ = 8.0 µm compared to the n = 1.49 of the acrylate polymer 14,12 . To quantify the effect on average AANR frequency and frequency range when core-shell lattices are composed of a-C cores and Ge shells, we repeated the previous series of band structure and EFC simulations, replacing Effective Refractive Index, nbeam only the core polymer material parameters with those of a-C (Table 3).…”