Observation of Complete Photonic Bandgap in Low Refractive Index Contrast Inverse Rod-Connected Diamond Structured Chalcogenides

Abstract

Three-dimensional complete photonic bandgap materials or photonic crystals block light propagation in all directions. The rod-connected diamond structure exhibits the largest photonic bandgap known to date and supports a complete bandgap for the lowest refractive index contrast ratio down to n high /n low ∼ 1.9. We confirm this threshold by measuring a complete photonic bandgap in the infrared region in Sn-S-O (n ∼ 1.9) 1 arXiv:1905.00404v1 [physics.optics] 1 May 2019 and Ge-Sb-S-O (n ∼ 2) inverse rod-connected diamond structures. The structures were fabricated using a low-temperature chemical vapor deposition process via a singleinversion technique. This provides a reliable fabrication technique of complete photonic bandgap materials and expands the library of backfilling materials, leading to a wide range of future photonic applications. Keywordsdirect laser writing, two-photon lithography, chemical vapor deposition, chalcogenide materials, photonic bandgap, three-dimensional photonic crystals Three-dimensional (3D) complete photonic bandgap (PBG) structures have been widely studied since their invention in 1987 by John 1 and Yablonovitch. 2 A complete PBG structure can prohibit photon propagation in any direction and this strong confinement of light can be exploited for applications ranging through high precision sensing, 3 ultralow power and ultrafast optical switches, 4 low threshold nanolasers, 5 high efficiency single photon sources, 6 and integrated photonic circuits. 7 However, such 3D PBG materials are difficult to fabricate. Currently two main techniques of fabrication have been demonstrated: bottom-up and top-down. The bottom-up method refers to schemes where nano-objects self-assemble into structures that then exhibit a PBG. 8,9 The top-down approach refers to creating 3D structures using etching, ion-milling, lithography or laser writing that then produce PBGs. Many of the top-down techniques involve miscellaneous fabrication steps such as waferfusion and micromanipulation, 10,11 while others such as single prism holographic lithography 12,13 do not allow for local modification for defects or waveguides. Alternatively, direct laser writing (DLW) using two-photon polymerization (2PP) allows for a variety of high refractive index contrast (RIC) 3D photonic crystal (PhC) structures with complete PBGs in near-infrared 14 and visible 15 regions to be realized. To fulfill the high RIC (> 2 : 1) requirement high index material (silicon or titanium dioxide) needs to be deposited into 3D Engineering and Physical Sciences Research Council (EPSRC) (EP/M009033/1, EP/M008487/1, EP/M024458/1, EP/N00762X/1). Acknowledgement This work was carried out using the cleanroom fabrication facilities of the Centre for Nanoscience and Quantum Information (NSQI), University of Bristol, and the Optoelectronics Research Centre (ORC), University of Southampton, and computational facilities of the Advanced Computing Research Centre (ACRC), University of Bristol.

Strongly Confining Light with Air-Mode Cavities in Inverse Rod-Connected Diamond Photonic Crystals

“…In this and previous works, we have focused our research on 3D photonic crystals, where we have shown partial photonic bandgaps (PBGs) in polymer photonic crystals that were fabricated using direct laser writing, exploiting two-photon polymerization (2PP)-based 3D lithography [11]. More recently, by backfilling polymer crystals with higher-index chalcogenide materials, a complete PBG has been demonstrated in technologically relevant wavelength regions (1.4-1.6 µm) [12]. This direct-writing templating technique is ideal for fabricating arbitrary 3D structures and could allow the selective writing of defects containing fluorescent material at the antinodes of cavities, i.e., the infiltration of the structure with liquid-containing quantum emitters, such as PbS colloidal quantum dots [13], single-walled carbon nanotubes (CNTs) [14], or coating with 2D materials [15,16].…”

Control over Light Emission in Low‐Refractive‐Index Artificial Materials Inspired by Reciprocal Design

“…In this publication, we define the RI contrast as the ratio of the refractive indices of two constituent media, n 1 / n 2 , where n 1 is larger than n 2 , so that the minimal contrast is 1. To increase the range of available materials for PBG applications, there have been considerable efforts to minimize the required RI contrast employing periodic [ 4,22–26 ] and aperiodic [ 21,27–35 ] structures. As aperiodic structures are not limited by the crystallographic theorem and thus are allowed for a more flexible positioning of Bragg peaks and smoother effective Brillouin zones, they are generally considered superior for low‐contrast CPBGs.…”

Harnessing Multi-Photon Absorption to Produce Three-Dimensional Magnetic Structures at the Nanoscale

“…The technique, which made use of pulsed lasers within the picosecond or femtosecond regime, was capable of defining any 3D geometry within a polymer, at a resolution of order 100 nm. From the 2000s onwards it has been used to great effect in order to realise photonic crystals [22][23][24][25][26], microfluidic channels [27] and cell scaffolds [28][29][30][31]. It would be another 15 years before the potential of two-photon lithography was exploited to realise 3D magnetic nanostructures.…”