INNOFOCUS
Laser fabricating of polymer materials can be applied in:
Complex 3D structure fabrication
Biological applications
Biological cells
Surface relief type optical element
3D photonic crystal
Optical waveguide coupler
Optical biomimetics
Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics. To approach the atomically thin limit, the use of 2D materials is an attractive possibility due to their high refractive indices. However, achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency. Here we report a universal method to transform 2D monolayers into ultrathin flat lenses. Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer, which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials. We achieved highly efficient 3D focusing with subwavelength resolution and diffraction limited imaging. The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications. Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.
This paper was titled “Diffraction-limited imaging with monolayer 2D material-based ultrathin flat lenses” and published on Light: Science & Applications. The first author is Dr. Han Lin.
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The development of ultrathin flat lenses has revolutionized the lens technologies and holds great promise for miniaturizing the conventional lens system in integrated photonic applications. In certain applications, the lenses are required to operate in harsh and/or extreme environments, for example aerospace, chemical, and biological environments. Under such circumstances, it is critical that the ultrathin flat lenses can be resilient and preserve their outstanding performance. However, the majority of the demonstrated ultrathin flat lenses are based on metal or semiconductor materials that have poor chemical, thermal, and UV stability, which limit their applications. Herein, we experimentally demonstrate a graphene ultrathin flat lens that can be applied in harsh environments for different applications, including a low Earth orbit space environment, strong corrosive chemical environments (pH = 0 and pH = 14), and biochemical environment. The graphene lenses have extraordinary environmental stability and can maintain a high level of structural integrity and outstanding focusing performance under different test conditions. Thus, it opens tremendous practical application opportunities for ultrathin flat lenses.
This paper was titled “Resilient Graphene Ultrathin Flat Lens in Aerospace, Chemical, and Biological Harsh Environments” and published on ACS Appl. Mater. Interfaces. The first author is Dr. Guiyuan Cao.
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Mid-infrared (MIR) represents crucial spectral region for applications in spectroscopy, sensing, imaging, security and industry screening, owing to the strong characteristic vibrational transitions of many important molecules. However, the current MIR compatible materials are fragile, hazardous, and costly, which hampers the performance of MIR devices. Here, we developed a versatile transmittance-based Kramers-Kronig method and obtained the optical properties of graphene oxide in the MIR region, unveiling its application potentials as a novel MIR compatible material. As an example, we demonstrated free-standing graphene oxide MIR polarizers with large extinction ratio (~ 20 dB) and controllable working wavelength up to 25 μm, by using the low-cost and flexible direct laser writing technique. Our transmittance-based KK method offers a versatile approach to obtain the optical properties of novel atomic-scale low-dimensional materials in the less developed MIR region and opens up opportunities in high performing functional MIR devices.
This paper was titled “Free-standing graphene oxide mid-infrared polarizers” and published on Nanoscale. The first author is Xiaorui Zheng.
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https://pubs.rsc.org/en/content/articlelanding/2020/nr/d0nr01619e/unauth#!divAbstract
Microbubbles acting as lenses are interesting for optical and photonic applications such asvolumetric displays, optical resonators, integration of photonic components onto chips, high-resolution spectroscopy, lithography, and imaging. However, stable, rationally designed, and uniform microbubbles on substrates such as silicon chips are challenging because of the random nature of microbubble formation. We describe the fabrication of elastic microbubbles with a precise control of volume and curvature based on femtosecond laser irradiated graphene oxide. We demonstrate that the graphene microbubbles possess a near-perfect curvature that allows them to function as reflective microlenses for focusing broadband white light into an ultrahigh aspect ratio diffraction-limited photonic jet without chromatic aberration. Our results provide a pathway for integration of graphene microbubbles as lenses for nanophotonic components for miniaturized lab-on-a-chip devices along with applications in high-resolution spectroscopy and imaging.
This paper was titled “Near-perfect microlenses based on graphene microbubbles” and published on Advanced Photonics. The first author is Dr. Han Lin.
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An ideal solar-thermal absorber requires efficient selective absorption with a tunable bandwidth, excellent thermal conductivity and stability, and a simple structure for effective solar thermal energy conversion. Despite various solar absorbers having been demonstrated, these conditions are challenging to achieve simultaneously using conventional materials and structures. Here, we propose and demonstrate three-dimensional structured graphene metamaterial (SGM) that takes advantages of wavelength selectivity from metallic trench like structures and broadband dispersion less nature and excellent thermal conductivity from the ultrathin graphene metamaterial film. The SGM absorbers exhibit superior solar selective and omnidirectional absorption, flexible tunability of wavelength selective absorption, excellent photothermal performance, and high thermal stability. Impressive solar-to-thermal conversion efficiency of 90.1% and solar-to-vapor efficiency of 96.2% have been achieved. These superior properties of the SGM absorber suggest it has a great potential for practical applications of solar thermal energy harvesting and manipulation.
This paper was titled “Structured graphene metamaterial selective absorbers for high efficiency and omnidirectional solar thermal energy conversion” and published on Nature Communications. The first author is Dr. Keng-Te Lin.
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Broadband strong light absorption of unpolarized light over a wide range of angles in a large-area ultrathin film is critical for applications such as photovoltaics, photodetectors, thermal emitters and optical modulators. Despite long-standing efforts in design and fabrication, it has been challenging to achieve all these desired properties simultaneously. We experimentally demonstrate a 12.5 cm2, 90-nm-thick graphene metamaterial with approximately 85% absorptivity of unpolarized, visible and near infrared light covering almost the entire solar spectrum (300–2,500 nm). The metamaterial consists of alternating graphene and dielectric layers; a grating couples the light into waveguide modes to achieve broadband absorption over incident angles up to 60°. The very broad spectral and angular responses of the absorber are ideal for solar thermal applications, as we illustrate by showing heating to 160 °C in natural sunlight. These devices open a novel approach to applications of strongly absorbing large-area photonic devices based on two-dimensional materials.
