We create electromagnetic environments with atomic-scale spatial structure and ultrafast temporal control — and study what they do to light, to quantum emitters, and to matter.
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Group leader
Professor of Nanophotonics, Niels Bohr Institute · University of Copenhagen
Maiken H. Mikkelsen is an experimental physicist working at the intersection of nanophotonics, quantum optics and nonlinear optics. Her research explores how electromagnetic fields structured on atomic and ultrafast scales can control — and sometimes transform — the interaction between light and matter.
Before joining the University of Copenhagen in 2026 she was a professor at Duke University, where she led the eight-university Meta-Imaging MURI and an NIH R01 program on point-of-care biosensors. She is a Fellow of Optica and received the American Physical Society's Maria Goeppert Mayer Award for her work in quantum nanophotonics. Her laboratory in Copenhagen is established with a DKK 35 million RECRUIT award from the Novo Nordisk Foundation.
From enhancement to new physics
Most optical materials are described by their intrinsic properties — refractive index, nonlinear susceptibility, emission lifetime, response time. But these are not properties of the material alone. They depend on the electromagnetic environment the material sits in, including the vacuum itself.
We build that environment to order. Our cavities confine light to gaps a few nanometers wide, where the field varies on the scale of a single exciton. Inside them, emitters radiate up to ten thousand times faster than in free space, nonlinear responses appear that no bulk coefficient predicts, and a slow material becomes an ultrafast detector.
Much of nanophotonics, including our own early work, has asked how strongly an optical process can be enhanced. We now ask a different question: can an electromagnetic environment beyond anything found in nature create behavior that could not exist otherwise?
Research
How are the rules of light–matter interaction rewritten when the field varies across a single emitter?
We fabricate optical cavities with gaps of a few nanometers, confining light to volumes more than ten thousand times smaller than a cubic wavelength. In this regime the usual rules of light–matter interaction stop applying.
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What can a single emitter do when the vacuum around it is engineered?
We place one, two, or a few quantum emitters inside nanogap cavities and study how the cavity rewrites their interaction with the vacuum — making, among other things, single-photon sources at telecom wavelengths with lifetimes of tens of picoseconds.
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Can the environment itself be changed faster than the matter inside it can respond?
Extreme confinement creates enormous fields and energy densities in nanoscale volumes, where a few nanometers of ordinary dielectric become an efficient source of harmonic generation. A femtosecond pump–probe laboratory, now being built, will let us follow these processes in time.
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Can a nanogap drive a material into states it cannot reach on its own?
A nanogap concentrates the optical field a hundredfold in a single 50 nm patch. A two-dimensional magnet or semiconductor under a cube can therefore be dressed by a field strong enough to reshape its energy levels, while the incident beam stays weak enough not to heat the sample.
Explore this areaSelected discoveries
Film-coupled nanocube cavities enhance the emission rate of embedded emitters more than a thousandfold while keeping the light bright and directional. This work identified the mechanisms behind the enhancement and showed that extreme Purcell enhancement need not come at the cost of brightness or directionality — the combination the group’s later single-photon sources depend on.
Akselrod et al., Nature Photonics 8, 835 (2014) · Read the paper
A single colloidal quantum dot in a nanogap cavity emits single photons at 1550 nm with a lifetime of tens of picoseconds — a spontaneous emission rate enhanced up to 10,000-fold, with blinking almost entirely suppressed — at room temperature and made entirely from solution-processed components.
Zhang et al., ACS Nano 19, 19035 (2025) · Read the paper
Diamond is centrosymmetric and has no bulk second-order nonlinearity. Inside nanogap cavities, a diamond film only 12 nanometers thick becomes a bright source of second-harmonic light, enhanced more than ten-million-fold, while several nonlinear processes run in the same cavity at once — a nanoscale frequency converter in a material with no bulk second-order response.
Shen et al., Nanophotonics 10, 589 (2021) · Read the paper
Pyroelectric detectors are limited by how fast heat can move. By structuring the absorber as a metasurface only nanometers thick, we made a pyroelectric photodetector with sub-nanosecond response and built-in spectral selectivity — and have since pushed the same idea to gigahertz speeds.
Stewart et al., Nature Materials 19, 158 (2020); Shin et al., Adv. Funct. Mater. 36, 2420953 (2026) · Read the paper
Silver nanocube metasurfaces patterned into micrometer-scale pixels, with six resonances spanning the visible and near-infrared, can be combined into 9,261 colors — enough to reconstruct a photograph in absorption at 560 dpi. The bird above is 2 mm across and made entirely of nanoscale cavities.
Stewart et al., Advanced Materials 29, 1602971 (2017) · Read the paper
An inkjet-printed immunoassay for the cardiac biomarker BNP, built directly inside nanogap cavities: antibodies on a nanometer-thin polymer brush over gold, capped with silver nanocubes. The cavity brightens the fluorescence more than a hundredfold and lowers the detection limit fourteen-fold. With Ashutosh Chilkoti’s group; supported by an NIH R01.
Cruz et al., Nano Letters 20, 4330 (2020) · Read the paper
Journal covers
Advanced Optical Materials Thin-film interference in diamond membranes 
ACS Nano Picosecond single photons from diamond 
Advanced Materials Metasurface pixels for multispectral imaging 
Advanced Materials Large-area metasurface perfect absorbers 
Science Picosecond control of a single electron spin Covers © Wiley-VCH, American Chemical Society and AAAS.
The lab
We are building the laboratory from the ground up in the Niels Bohr Institute's new building, established with a DKK 35 million RECRUIT award from the Novo Nordisk Foundation. Instruments arriving through 2027:
Nanofabrication is carried out in the NBI nanofabrication facilities and the DTU Nanolab cleanroom. The Niels Bohr Institute hosts world-leading groups in quantum optics, quantum photonics, and condensed-matter physics, and Copenhagen has strong quantum photonics and 2D-materials communities at both NBI and DTU.
Join us in Copenhagen
We are building a new research group and looking for curious experimentalists who want to explore fundamental questions at the boundaries of optics, materials, and quantum science. The people who join now will be founding members of the lab — building the first experiments with us, setting up instruments as they are delivered, and producing its earliest results.
