Haigui Yang

Large area and broadband ultra-black absorber using microstructured aluminum doped silicon films

A large area and broadband ultra-black absorber based on microstructured aluminum (Al) doped silicon (Si) films prepared by a low-cost but very effective approach is presented. The average absorption of the absorber is greater than 99% within the wide range from 350 nm to 2000 nm, and its size reaches to 6 inches. We investigate the fabrication mechanism of the absorber and find that the Al atom doped in silicon improves the formation of the nanocone-like microstructures on the film surface, resulting in a significant decrease in the reflection of incident light. The absorption mechanism is further discussed by experiments and simulated calculations in detail. The results show that the doped Al atoms and Mie resonance formed in the microstructures contribute the broadband super-high absorption.

Near-Infrared Absorption Enhancement Mechanism Investigations of Deep-Trench Silicon Microstructures Covered with Gold Films

We design a deep-trench microstructure covered with thin gold films to enhance near-infrared absorption of silicon material. This deep-trench microstructure exhibits a much higher absorption compared with plane nanoantenna arrays. We investigate its absorption enhancement in detail and find that the trench-shaped plasmonic waveguide greatly contributes an absorption enhancement by concentrating light effectively. Further, we clarify the influence of both trench depth and gold films covering on different positions of deep trench on the absorption. Finally, we use surface plasmon polaritons offered by plasmonic waveguide to explain well the significant enhancement of near-infrared absorption.

Roughness reduction of large-area high-quality thick Al films for echelle gratings by multi-step deposition method.

Generally, echelle grating ruling is performed on a thick Al film. Consequently, high-quality large-area thick Al films preparation becomes one of the most important factors to realize a high-performance large-size echelle grating. In this paper, we propose a novel multi-step deposition process to improve thick Al films quality. Compared with the traditional single-step deposition process, it is found that the multi-step deposition process can effectively suppress large-size grains growth resulting in a low surface roughness and high internal compactness of thick Al films. The differences between single- and multi-step deposition processes are discussed in detail. By using multi-step deposition process, we prepared high-quality large-area Al films with a thickness more than 10 μm on a 520 mm × 420 mm neoceramic glass substrate.

Si-based near-infrared narrowband absorber based on square Au patches

We design a periodic Au patch-shaped microstructure covering on an Si substrate. This microstructure exhibits a designable near-infrared narrowband absorption from 1100 to 1500 nm. We investigate its absorption mechanism by the metal-insulator-metal waveguide theory and find that the combination of the plasmonic effect and cavity effect contributes an efficient absorption by calculating the electric field distribution numerically. We further analyze the relationship between the absorption spectra and electric field distributions of the structure with different patch lengths, by which we clarify why the narrowband absorption peak can be linearly shifted by varying the length of the Au patch.

Radial-quality uniformity investigations of large-area thick Al films

Abstract. The fabrication of high-quality large-area thick Al films with a thickness around 10  μm or even more is one of the most important factors to realize high-performance large-size echelle gratings. During the deposition process of large-area Al films, Al film quality generally exhibits a different behavior along the radius (R) direction, which seriously affects the performance of echelle gratings. In this study, for the first time, we investigate the radial-quality uniformity of large-area (R=400  mm) thick (>10  μm) Al films in detail. We not only analyze the radial-quality difference of Al films prepared by the traditional electron-beam evaporation process, but also significantly improve the radial-quality uniformity of large-area thick Al films by using a coevaporation process. By comparing two kinds of film coating processes, we clarify the origin of the radial-quality difference of Al films, and prepare large-area thick Al films with excellent radial-quality uniformity.

A Super Meta-Cone Absorber for Near-Infrared Wavelengths

We present a meta-cone absorber based on metamaterials which can absorb nearly all incident light in the near-infrared spectrum. The absorber has an ultrahigh absorption with a broad receiving angle and independence of polarization state. This absorption enhancement can be attributed to the excitation of slow light mode and localized surface plasmon resonances (LSPR). In addition, we use slow light theory to explain why incident light with different wavelengths are trapped at different positions. We believe our work will provide a promising candidate as absorbing elements in technical applications and scientific research.

Novel aluminum plasmonic absorber enhanced by extraordinary optical transmission.

We report a theoretical and experimental study on a novel type of aluminum super absorber which exhibits a near perfect absorption based on the surface plasmon resonance in the visible and near-infrared spectrum. The absorber consists of Ag/SiO2/Al triple layers in which the top Al layer is patterned by a periodic nano hole array. The absorption spectrum can be easily controlled by adjusting the structure parameters including the radius of the nano hole and the maximal absorption can reach 99.0% in theory. We completely analyze the SPP and LSP modes supported by the metal-dielectric-metal structure and their contribution to the ultrahigh absorption. On this basis, we find a novel method to enhance the absorption via the simultaneous excitation of SPP at different interfaces theoretically and experimentally. Moreover, for the first time we clarify the EOT caused by the nano hole array can enhance the absorption by experiment, which is not reported in previous works. This kind of absorber can be fabricated by low-cost colloidal sphere lithography and the use of stable Al overcomes the disadvantages brought by the noble metal, which make it a more appropriate candidate for photovoltaics, spectroscopy, photodetectors, sensing, and surface enhanced Raman scattering.

Silicon-based multilayer gratings with a designable narrowband absorption in the short-wave infrared

We demonstrate an Al/Si multilayer-grating microstructure covered on Si substrate. This microstructure presents a designable narrowband absorption in short-wave infrared (SWIR) waveband (2.0 μm-2.3 μm). We investigate its absorption mechanism by both modeling and simulations, and explain the results well with metal-insulator-metal and Fabry-Perot cavity theory. Furthermore, we present the absorption of fabricated multilayer-grating microstructure through experiment, and discuss the influence of structures lateral angle on its absorption in detail. This work provides the possibility to design Si-based devices with designable working bands in SWIR spectrum.

Compensating the Degradation of Near-Infrared Absorption of Black Silicon Caused by Thermal Annealing

We propose the use of thin Ag film deposition to remedy the degradation of near-infrared (NIR) absorption of black Si caused by high-temperature thermal annealing. A large amount of random and irregular Ag nanoparticles are formed on the microstructural surface of black Si after Ag film deposition, which compensates the degradation of NIR absorption of black Si caused by thermal annealing. The formation of Ag nanoparticles and their contributions to NIR absorption of black Si are discussed in detail.

Microcavity electrodynamics of hybrid surface plasmon polariton modes in high-quality multilayer trench gratings

In common plasmonic structures, absorption and radiation losses are often mutually restricted and can seriously influence the device performance. The current study presents a compound structure composed of multilayer grating stripes and multilayer shallow trenches. A small depth was adopted for the trench configuration to exclude the extra bend loss. These two sections supported Fabry–Perot resonance and cavity modes, respectively, with hybrid modes formed through intercoupling. In addition, the total loss for the entire framework was clearly reduced due to the introduction of the trench geometry, indicating that both absorption and radiation losses were successfully taken into consideration in the compound structure. Significantly, such a low loss realized by the hybridization of surface plasmon polariton modes has rarely been seen before. Moreover, the debatable relationship between the total and partial quality factors was described for the first time based on a hybrid mode analysis to establish a new approach to investigate the different resonance modes. In the detailed calculation process, the relative electric field intensity was first adopted to stipulate the effective areas for the various modes, which is more reasonable than using the common definition that is based on a unit structure. The multilayer trench grating exhibited a relatively low loss without weakening energy localization, which is significant in the design of plasmonic devices.Plasmonic gratings: finding quality in the trenchesLosses associated with confining surface waves inside metal–insulator–metal waveguides can be minimized by optimizing trench structures in microscale gratings. Jinsong Gao from the Chinese Academy of Sciences and colleagues used direct laser patterning to create 450-nanometer deep periodic patterns in silicon wafers, then coated the waveguide with five alternate aluminum and silicon layers. In the higher, stripe-shaped portions of the device, multiple modes of trapped surface plasmon polaritons appeared, following a pattern known as Fabry-Pérot resonance. Trenches, however, had surface waves generated by the microcavity shape. By customizing the grating dimensions, the team merged the two types of resonances into new modes with exceptionally low levels of radiation and absorption loss. Analytical treatments revealed quality factors of the hybrid modes were better predicted using relative electric field intensities than periodic cell lengths.