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Metasurface Holograms

Self-calibrated flexible holographic curvature sensor

Optical curvature sensors find regular use in deformation analysis, typically requiring pre-calibration and post–processing of gathered data. In this paper, we present a self-calibrated curvature sensor based on flexible holographic metasurfaces operating in the visible range. In contrast to existing solutions, the sensor can be fabricated independently from target objects and provides an immediate readout of their curvature. The sensor consists of distinct patterned areas that create images of a reference scale and of a position indicator, which shift with respect to each other, as the metasurface is deformed. We validate the results of our sensor with an external calibration and critically discuss the types… Read More »Self-calibrated flexible holographic curvature sensor

ZrO2 metasurface

ZrO2 Holographic Metasurfaces for Efficient Optical Trapping in The Visible Range

In this paper, we introduce a new material platform for holographic metasurfaces. Ceramic-based metasurfaces are ideally suited for biophotonic applications, where the operating wavelength goes down to the blue region of the visible range and below. Here, we exploit the unique properties of this platform by demonstrating the first on-chip trapping using blue light.

Optically Manipulated Micromirrors for Precise Excitation of WGM Microlasers

Whispering gallery mode microlasers are highly-sensitive refractive index sensors that are widely explored for biophotonic and biomedical applications. These microlasers are used for excitation and collection of the emitted light, typically utilizing microscope objectives at normal incidence. However, this limits the choice of the oscillation plane of the modes. To overcome this limitation, in this paper, we present a new platform that enables the excitation of microlasers from various directions using an optically manipulated micromirror. This scheme enables precise sensing of the environment surrounding the microlasers along different well-controlled planes. Furthermore, the platform’s capability to perform a time-resolved experiment of dynamic sensing using a polystyrene… Read More »Optically Manipulated Micromirrors for Precise Excitation of WGM Microlasers

Thin-film polymeric metasurfaces for visible wavelengths

Photonic Metasurfaces (MSs) have now become one of the key platforms to encode multiplexed holographic information, using e.g. wavelength, angular momentum, angle of incidence and polarization of the light source. Traditionally, the meta-atoms composing the MSs are made structuring at subwavelength scales composite materials. However, while this enables a variety of interesting scattering properties that can be used to add functionalities to MSs, using a single material would often be preferable, to facilitate the design and fabrication of the devices. In this paper, we demonstrate a new class of holographic metasurfaces made by a simple polymeric membrane for holographic applications. Our devices retain good efficiency… Read More »Thin-film polymeric metasurfaces for visible wavelengths

On-Chip Optical Trapping with High NA Metasurfaces

Photonic metasurfaces can be used to create strongly focused beams for optical trapping applications. Here, we design and fabricate holographic metasurfaces with numerical aperture up to 1.2, and trapping stiffness greater than 400 pN/µm/W, which perform as well as a microscope objective with a comparable numerical aperture. In this work, we analyze how the trapping performance depends on the metasurface dimension, down to areas as small as 0.001 mm2. Finally, we demonstrate the photonic metasurfaces can create multi-site optical tweezers, for the trapping of extended objects, like photonic membranes.

Shape Dependent Conformable Holographic Metasurfaces

In this paper, we report on the design, fabrication, and experimental demonstration of conformable holographic metasurfaces. Here, we show that the produced holographic image changes as the metasurface is applied to targets with different shapes. The demonstration is based on a reflective type metasurface, where the reflected polarization is perpendicular to that of the incident light. In addition, we discuss critically how the parameters of the metasurface determine the quality of the images produced and the ability to produce independent images.

Two-tier manipulation of holographic information

In this paper, published in Optics Express, we design and experimentally demonstrate the two-tier manipulation of optical information using holographic metasurfaces. Our devices encodes different information that can be retrieved if two keys are simultaneously used. Here, one key is the wavelength used to probe the holographic metasurfaces. The other key is the medium in which the metasurface is held. Specifically, one image is obtained for visible light at 705nm and air and a different, uncorrelated image is obtained for a wavelength of 750nm in water. The key element that enables our technology is the use of resonant meta-atoms (the unit cell of the  metasurface)… Read More »Two-tier manipulation of holographic information

ERC PoC – Holophrase

[Edit February 2023: Holophrase is now funded by the EPSRC, due to the UK-EU ongoing negotiations.] We are happy to share the news that the group has been awarded an ERC Proof of Concept grant, to develop an integrated on-chip pH sensor. HolopHrase is based on the ERC consolidator grant AMPHIBIANS, which introduces the metasurfaces technology in microfluidic environments. With HolopHrase, we will develop a flexible solution for the real time, label free, quantitative optical imaging readout of the pH level of a liquid solution. Our approach brings together the ease of access, simplicity, and cost of bulkier solutions, with the accuracy and level of… Read More »ERC PoC – Holophrase

Flexible Patches for mm-Wave Holography

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In a paper, published in Applied Physics Letters, we present a flexible holographic metasurface operating in the mm-wave range. The implementation of this metasurface is a three-layer structure using c-rings to encode the hologram and is implemented in both rigid and flexible designs. Furthermore, we present simulations and experimental results of the resultant holographic images. This work is of practical relevance for retrofitting existing mm-wave equipment for applications related to antennas (e.g. for 5G) and electromagnetic shielding.

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