Diamond-structured Photonic Crystal Research Articles

Systematic design study of waveguides and waveguide bends in diamond-structured photonic crystals

The lack of a systematic design strategy to precisely control bending and guiding of photons in three dimensions, as well as the requirement of advancements in the fabrication technology for realizing large-area, defect-free three-dimensional (3D) photonic crystals, has been the main hurdle toward exploiting the potential of three-dimensional photonic crystals. Here, we demonstrate a new, to the best of our knowledge, design methodology for 3D waveguides and bends in diamond-structured photonic crystals. The manipulation of photons in 3D by incorporating two combinations of four different linear defect configurations in two different photonic crystal topologies of a diamond lattice, namely rod-connected diamond and inverse-rod-connected diamond, has been successfully demonstrated. We have also shown 90-deg waveguide bends with near zero dB bending loss.

Enhanced Transmission Performance of a Dipole Antenna Based on a Ceramic Diamond-Structure PBG Substrate with a Defect Cavity

The radiation performance of a dipole antenna on a diamond-structured photonic crystal (PC) substrate with point defects fabricated using three-dimensional (3D) printing technology has been investigated. Meanwhile, according to the reflection properties of the PCs, corresponding dipole antennas were fabricated and packaged with standard coaxial lines. The experimental results showed a strong radiation frequency of the dipole antenna at about 13 GHz, in basic agreement with the strongest reflection frequency of the PCs with point defects. The experimental results also show that the maximum gain of the major lobe in the dipole antenna was close to −67 dB, while the angular range of the major lobe was 5–55°. The maximum gain of the major lobe increased to −60 dB in the composite antenna, representing an improvement of 7 dB compared with the dipole antenna, while the width range of the major lobe was 240–270°. These results show that the use of such substrates based on diamond-structure PCs with point defects could significantly improve the gain and directivity of the antenna, providing a basis for engineering applications.

Multi-ceramic coupling diamond-structured photonic crystals based on rapid prototyping technology and its controllable microwave electromagnetic forbidden gap properties

The multi-ceramic coupling diamond-structured photonic crystals containing alumina and yttria simultaneously were successfully fabricated by rapid prototyping based on stereolithography and multi-step gel-casting process. The lattice constant of the photonic crystal structures was chosen as 7mm and the measured forbidden gap range lies between 27.2GHz and 34.9GHz. The gradually varied solid loading in volume of Al2O3 powder and its controllable electromagnetic forbidden gap properties were investigated in such photonic crystals. It was found that, as the solid loading of Al2O3 powder increased, the electromagnetic forbidden gap width gradually increased and the center frequency shifted to a lower frequency when electromagnetic waves transmitted along the coupling direction of photonic crystals. When the solid loading reached 60vol%, electromagnetic forbidden gap of the photonic crystals was observed from 27.2GHz to 34GHz, and the forbidden gap width was 6.8GHz which was 126.4% of that of the yttria photonic crystal (the forbidden gap from 30.9GHz to 35.9GHz) and 115.3% of that of the alumina photonic crystal (60vol%, the forbidden gap from 26.4GHz to 32.3GHz). These results indicate that a diamond-structured photonic crystal with multi-ceramic coupling could effectively expand the electromagnetic forbidden gap width and may be beneficial for applications of photonic crystals in device. Moreover, this work offers a rapid prototyping technology to three-dimensional photonic crystals with considerable flexibility of materials choice.

Color Production in Blue and Green Feather Barbs of the Rosy-faced Lovebird

We study experimentally and theoretically the coloration mechanisms of blue and green feather barbs in the rosy-faced lovebird (Agapornis roseicollis). Structural characterizations reveal that both the blue and green barbs contain a similar rod-connected amorphous diamond-structured photonic crystal (RAD-PC), producing basically a non-iridescent blue structural color. Numerical simulations show that the existence of a photonic pseudogap in the photonic density of states of the RAD-PC is the physical origin of the non-iridescent blue coloration. The green color in the green barbs is a mixed color coming from the blue structural color in the RAD-PC and the yellow color in the cortex layer that contains a yellow pigment. The optical function of the yellow pigment for achieving a saturated green color is discussed. The interesting coloration mechanisms unraveled may help us get in-depth understandings of the ingenious strategies of color production in nature and valuable inspirations as well.

Correction for Yin et al., Amorphous diamond-structured photonic crystal in the feather barbs of the scarlet macaw

Correction for Yin et al., Amorphous diamond-structured photonic crystal in the feather barbs of the scarlet macaw

Amorphous diamond-structured photonic crystal in the feather barbs of the scarlet macaw

Noniridescent coloration by the spongy keratin in parrot feather barbs has fascinated scientists. Nonetheless, its ultimate origin remains as yet unanswered, and a quantitative structural and optical description is still lacking. Here we report on structural and optical characterizations and numerical simulations of the blue feather barbs of the scarlet macaw. We found that the sponge in the feather barbs is an amorphous diamond-structured photonic crystal with only short-range order. It possesses an isotropic photonic pseudogap that is ultimately responsible for the brilliant noniridescent coloration. We further unravel an ingenious structural optimization for attaining maximum coloration apparently resulting from natural evolution. Upon increasing the material refractive index above the level provided by nature, there is an interesting transition from a photonic pseudogap to a complete bandgap.

Diamond-Structured Photonic Crystals with Graded Air Spheres Radii.

A diamond-structured photonic crystal (PC) with graded air spheres radii was fabricated successfully by stereolithography (SL) and gel-casting process. The graded radii in photonic crystal were formed by uniting different radii in photonic crystals with a uniform radius together along the Г-Х <100> direction. The stop band was observed between 26.1 GHz and 34.3 GHz by reflection and transmission measurements in the direction. The result agreed well with the simulation attained by the Finite Integration Technique (FIT). The stop band width was 8.2 GHz and the resulting gap/midgap ratio was 27.2%, which became respectively 141.4% and 161.9% of the perfect PC. The results indicate that the stop band width of the diamond-structured PC can be expanded by graded air spheres radii along the Г-Х <100> direction, which is beneficial to develop a multi bandpass filter.

Ultra-wide bandgap of gradient dielectric constant photonic crystal

A diamond-structured photonic crystal (PC) of gradient dielectric constant realized by combining alumina PC with two different solid loadings of alumina powder in the slurry was fabricated using the stereolithography (SL) and gel-casting process. The ultra-wide bandgap was experimentally confirmed by reflection and transmission measurements and simulated by the Finite Integration Technique (FIT). It was found that, the bandgap width of the PC with gradient dielectric constant increased remarkably in comparison with that of the normal alumina PC and reached 8GHz, which was 117.6% of that of the alumina PC(60vol.%). The maximum attenuation attained from the fabricated sample is −63.4dB. The results indicate that the diamond-structured PC with gradient dielectric constant could effectively expand the bandgap width of the PC. The simulation result agreed well with the measurement result by FIT.

Free-space carpet-cloak based on gradient index photonic crystals in metamaterial regime

A free-space broadband carpet-cloak, designed based on transformations optics and quasi-conformal mapping, was realized with all-dielectric gradient index rod-connected diamond-structured photonic crystals (PCs) in metamaterial regime. Complex three-dimensional sample with smooth continuous changing unit cells was fabricated precisely by stereolithography (SL) using photo-curable resin. Thus, by gradually varying the unit cell constitutive parameters of the diamond-based PCs with nearly isotropic properties, the required complex spatial distribution of the refractive index profile was ideally achieved to reduce the scattering of the electromagnetic wave. The non-resonant property of the sub-wavelength PCs unit cell resulted in broad bandwidth and relatively low loss.

Strongly Modified Spontaneous Emission Rates in Diamond-Structured Photonic Crystals

The spontaneous emission decay dynamics of nanocrystal quantum dots embedded into biotemplated titania photonic crystals with a diamond-based lattice are investigated. Modification of the decay rate of quantum dot emission over wide frequency bandwidths in the visible by the photonic crystals is observed. Frequency-dependent analysis reveals both inhibition and enhancement of emission with a radiative lifetime variation by more than a factor of 10.

Diamond-structured photonic crystals.

Certain periodic dielectric structures can prohibit the propagation of light for all directions within a frequency range. These 'photonic crystals' allow researchers to modify the interaction between electromagnetic fields and dielectric media from radio to optical wavelengths. Their technological potential, such as the inhibition of spontaneous emission, enhancement of semiconductor lasers, and integration and miniaturization of optical components, makes the search for an easy-to-craft photonic crystal with a large bandgap a major field of study. This progress article surveys a collection of robust complete three-dimensional dielectric photonic-bandgap structures for the visible and near-infrared regimes based on the diamond morphology together with their specific fabrication techniques. The basic origin of the complete photonic bandgap for the 'champion' diamond morphology is described in terms of dielectric modulations along principal directions. Progress in three-dimensional interference lithography for fabrication of near-champion diamond-based structures is also discussed.