Observation of Quadratic (Charge‐2) Weyl Point Splitting in Near‐Infrared Photonic Crystals (Laser Photonics Rev. 16(1)/2022)

Over a decade ago, theorists predicted that photonic crystals active at visible and near-infrared wavelengths would possess a variety of exciting optical properties. Only in the last several years, however, have experimentalists begun to build materials that realize this potential in the laboratory. This lag between experiment and theory is primarily due to the to the challenges associated with fabricating these unique materials. As the term “crystal” suggests, these samples must consist of highly perfect ordered arrays of solids. However, unlike conventional crystals, which exhibit order on the angstrom length scale, photonic crystals must have order on the submicrometer length scale. In addition, many of the most valuable properties of photonic crystals are only realized when samples possess a “full” photonic bandgap. For such systems, large dielectric contrasts and particular crystal symmetries create a range of frequencies over which light cannot propagate. Realizing the nanoscopic architectures required to form such systems is a challenge for experimentalists. As a result, fabrication schemes that rely on lithographic techniques or spontaneous assembly have been a focus in the development of the field.

Download Full-text

An Omnidirectional Reflector and Microcavity Resonatorvia the Sol-Gel Method

MRS Proceedings ◽

10.1557/proc-597-75 ◽

1999 ◽

Vol 597 ◽

Cited By ~ 1

Author(s):

Kevin M. Chen ◽

Andrew W. Sparks ◽

Hsin-Chiao Luan ◽

Desmond R. Lim ◽

Kazumi Wada ◽

...

Keyword(s):

Photonic Crystals ◽

Near Infrared ◽

Incident Angle ◽

Sol Gel ◽

Defect Layer ◽

Cavity Resonance ◽

Near Infrared Reflectance ◽

Gel Method ◽

Sol Gel Method ◽

Theoretical Predictions

AbstractThin films of sol-gel SiO2 and TiO2 were used to fabricate two types of onedimensional photonic crystals: an omnidirectional reflector and microcavity resonator. The reflector consisted of six SiO2/TiO2 bilayers, designed with a stopband in the near infrared. Reflectance measurements over an incident angle range of 0–80° showed an omnidirectional band of 70 nm, which agrees with theoretical predictions for this materials system. The microcavity resonator consisted of a TiO2 Fabry-Perot cavity sandwiched between two SiO2/TiO2 mirrors of three bilayers each. We have fabricated a microcavity with resonance at λcavity = 1500nm and achieved a quality factor of Q=35. We measured a modulation in the cavity resonance frequency with a change of defect layer thickness and incident angle of light. This work demonstrates the feasibility of fabricating photonic crystals via the sol-gel method.

Download Full-text

Natural slab photonic crystals in centric diatoms

10.1101/838185 ◽

2019 ◽

Author(s):

Johannes W. Goessling ◽

William P. Wardley ◽

Martin Lopez Garcia

Keyword(s):

Photonic Crystal ◽

Photonic Crystals ◽

Spectral Range ◽

Near Infrared ◽

Light Regulation ◽

Visible Spectral Range ◽

Mating Strategies ◽

Unit Cell ◽

Critical Parameters ◽

Centric Diatom

AbstractNatural photonic crystals can serve in mating strategies or as aposematism for animals, but they also exist in some photosynthetic organisms, with potential implications for their light regulation. Some of the most abundant microalgae, named diatoms, evolved a silicate exoskeleton, the frustule, perforated with ordered pores resembling photonic crystals. Here we present the first combined experimental and theoretical characterization of the photonic properties of the diatom girdle, i.e. one of two structures assembling the frustule. We show that the girdle of the centric diatom Coscinodiscus granii is a well-defined slab photonic crystal, causing, under more natural conditions when immersed in water, a pseudogap for modes in the near infrared. The pseudogap disperses towards the visible spectral range when light incides at larger angles. The girdle crystal structure facilitates in-plane propagation for modes in the green spectral range. We demonstrate that the period of the unit cell is one of the most critical factors for causing these properties. The period is shown to be similar within individuals of a long-term cultivated inbred line and between 4 different C. granii cell culture strains. In contrast, the pore diameter had negligible effects upon the photonic properties. We hence propose that critical parameters defining the photonic response of the girdle are highly preserved. Other centric diatom species, i.e. Thalasiosira pseudonana, C. radiatus and C. wailesii, present similar unit cell morphologies with various periods in their girdles. We speculate that evolution has preserved the photonic crystal character of the centric girdle, indicating an important biological functionality for this clade of diatoms.

Download Full-text