Projects & Labs

Here we describe our current projects (as of October 2025) and our experimental capabilities.

Nanophotonics with van der Waals materials

New possibilities with van der Waals crystals

While monolayer and few-layer transition metal dichalcogenides (TMDs) are well-known for their excitonic properties, we focus on the quasi-bulk regime (from a few atomic layers up to hundreds of nanometers). These thicker van der Waals (vdW) structures offer a versatile platform for nanophotonics, providing higher refractive indices and significantly larger birefringence than traditional silicon or III-V semiconductors.

A central pillar of our current work is the exploration of nonlinear optics in 3R-MoS2. Ulike the common 2H-phase, the 3R-polytype lacks inversion symmetry regardless of layer thickness. This allows us to utilize strong second-order nonlinear responses in robust, high-index structures that remain transparent across the visible and near-infrared spectra. An exciting possibility is to use spontaneous parametric down-conversion (SPDC) in 3R-MoS2 metasurfaces and waveguides to generate entangled photon pairs for quantum applications. This perfectly works at room temperature.

Fabrication, heterointegration, and advanced device architectures

Our fabrication approach combines mechanical exfoliation with electron-beam lithography and dry etching to pattern these materials into metasurfaces, waveguides and nanoantennas. Heterointegration with traditional photonic platforms, such as silicon photonics and silicon nitride (SiN), is straightforwardly enabled by the inherent van der Waals forces in these layered crystals. Because these forces eliminate the requirement for lattice matching, we can seamlessly integrate vdW structures with established photonic integrated circuits, bypass traditional growth and wafer bonding constraints, and create hybrid material systems on a single chip.

This material platform also allows for the creation of complex architectures through the vertical stacking and twisting of layers, effectively extending the "twistronics" concept to the quasi-bulk regime. By combining these unique structural degrees of freedom we aim to realize a new generation of high-efficiency nonlinear nanophotonic elements. These previously inaccessible photonic structures offer a path toward sophisticated light control and enhanced light-matter interaction in both classical and quantum regimes.

Strong light-matter interaction and nano-magnetism in 2D magnets and their heterostructures

Here we focus on studies of the strong light-matter interaction in 2D materials embedded in optical microcavities and coupled to various photonic structures.

New states of the matter, exciton-polaritons emerge in these structures, which provide a particularly rich phenomenology in atomically thin TMDs as well as in emerging magnetic semiconductors.

In a large family of layered crystals the properties range from superconductors and metals, to semiconductors and insulators. Properties of such quantum materials in a few-atomic-layer form are strongly influenced by the quantum confinement of the electronic excitations due to the extreme crystal thinness.

Surprisingly, a family of layered magnetic materials exists, which preserve their antiferromagnetic or ferromagnetic properties even in an atomic monolayer form. Such 2D materials will revolutionise electronics, memory devices, sensing and will have broad applications in quantum technologies, particularly in combination with other layered semiconductors.

Here we explore novel magnetic few-atomic-layer materials, work on advancing their fabrication, and develop methods for combining such materials with other 2D monolayer crystals such as TMDs or integrating them with photonic structures such as 1D photonic lattices.

The goal is to fabricate and explore novel types of opto-electronic devices taking advantage of various magnetic proximity effects generated by 2D magnetic materials on the nanoscale and to find ways of controlling magnetism with light.

Our recent focus has been on CrSBr, a fascinating antiferromagnetic semiconductor with strong exciton signatures, high Neel temperature and low-magnetic field switching into the ferromagnetic state. We learn how to control its magnetism by light in the strong light-matter interaction regime.

Topological photonic crystal made from a 70 nm thick flake of WS2. Flakes up to 300 micron in size are deposited on a carrier substrate (SiO2 in this case, but can be gold or any other dielectric of metal). Following electron beam lithography, the tiny triangular holes (side about 120 nm) are etched using reactive ion etching.

Photoluminescence (PL) from a monolayer WSe2 deposited on WS2 nanoantennas placed on gold. Bright yellow spots correspond to the positions of nanoantennas

Strong light-matter interaction observed in a tunable microcavity with a bilayer MoS2 (schematic in panel a). Collaboration with ultrafast spectroscopy group in Milan and theorists in Exeter. MoS2 bilayers are quite unique as in addition to the intralayer excitons they also have interlayer excitons formed from electrons and holes residing in different monolayers, and thus called dipolar excitons (after the permanent electric dipole of the exciton). The interlayer excitons in MoS2 bilayers have a large oscillator strength, so they can strongly interact with light and form dipolar polaritons (panel c above), which as we find, show stronger nonlinear properties.

Results of the collaborative project between our group, 2D materials specialists from Manchester and theorists from INL (Portugal). a Microscope image of the sample: multi-layered CrBr3, monolayer MoSe2, and hBN encapsulation layers. b Photoluminescence spectrum (T=4.2K) from MoSe2 monolayer attached to ferromagnetic CrBr3. c, d Schematics of a MoSe2/CrBr3 heterobilayer structure used in the density functional theory calculations, viewed from the side (c) and top (d), where the supercell is highlighted. e The DFT calculated electronic band structure of the MoSe2/CrBr3 heterobilayer, projected on the host material.

Our labs

Our expertise is in photonics and magneto-optics of nanostructured semiconductors. Altogether the group occupies 5 state-of-the-art laboratories. Three dedicated high-spec optical laboratories (including a vector-magnet magneto-optics and Raman set-up) and shares access to several other state-of-the-art optics laboratories in the Semiconductor Photonics and Quantum Technologies cluster (former LDSD group). We have established a 2D materials fabrication facility (a dedicated lab) including a glovebox with a micro-printing setup that ensures high quality heterogeneous integration and heterostructure assembly as well as allows working with air-sensitive 2D materials. Finally, we have launched a new Near-field Optical Imaging and Spectroscopy Centre (NOSC), where we have access to a range of tip-enhanced optical techniques and nano-spectroscopy.

Several of our set-ups are quite unique, even among the world leading optics groups. For example, we have a tunable Fabri-Perot microcavity set-up installed in a vector magnetic field cryostat where 4.5T can be rotated in 2D plane. This cryostat also has 9T maximum vertical magnetic field. The NOSC lab has a unique combination of excitation lasers and detectors in a wide range of wavelength including visible, near-infrared and mid-infrared.

The Attocube cryostat with a vector magnet (9T vertical and 4.5T rotated in the vertical plane) houses our unique cryogenic scanning microcavity set-up. The lab is equipped with a spectrometer and liquid nitrogen cooled CCD.

Scott Dufferwiel is working on a set-up combining a vector magnet and a scanning microcavity. June 2016. The lab is now further equipped with a supercontinuum laser tunable from 300 to 2000 nm.

Microscopes in one of the labs used for sample fabrication and for characterisation of nano-photonic devices in ambient conditions.

Set-up for cryogenic ultra-low frequency Raman spectroscopy uniquely designed for studies of magnetic and superconducting layered and atomically thin materials. Oscar Hutchings is aligning the set-up. Autumn 2020.

A typical micro-photoluminescence and micro-reflectance set-up for spectroscopy from cryogenic to room temperature, a work-horse of our experiments replicated in several labs.

Flake transfer set-up in a nitrogen-purged glovebox. The set-up will be equipped with optical characterisation allowing to measure air-sensitive materials and structures as soon as they've been made. July 2022.

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