Astronomy and astrophysics

Direct imaging of extrasolar planets

The combination of the starlight being extremely much brighter than the orbiting planet and that the planet is very close to its host star makes it very difficult to direct image an extrasolar planet. We have therefore during the last 10 years been working on the design and fabrication of a new type of diamond coronagraph, a so-called annular groove phase mask (AGPM). This coronagraph consists of so called subwavelength gratings, which means that the grating period is shorter than the wavelength. Due to extremely small grating period one can say that the light will not be able to resolve the grating, and we will instead be able to manipulate the polarization of the light (no diffraction at higher orders as with a grating with larger period than the wavelength). This new type of coronagraph, that manipulates the polarization of the light in a special way, is able to block the light from a star without affecting the light of a nearby planet over a wide range of wavelengths. In this way we can say that we are able to hide the star to unveil the hidden planet (see animation 1 and animation 2). The main goal of this project is to find extrasolar planets by direct detection, which means that one gets access to the photons from the planet. Since this component works at several wavelengths it is also possible to perform spectroscopy of the light from the extrasolar planet, and thus making it possible to look for biosignatures (e.g. habitable planet). Up to now we have been very successful in the design and fabrication of these coronagraphs and several of the components have already been installed in the world leading ground based telescopes; Very Large Telescope in Chile, KECK Observatory in Hawaii and The Large Binocular Telescope in Arizona. We have close collaborations with colleagues at the University of Liège (Belgium), Observatoire de Paris (France), European Southern Observatory, California Institute of Technology (USA) and Jet Propulsion Laboratory NASA (USA). The strength of the AGPMs has already been proven by presenting the first image of the brown dwarf called HIP79124 B and by presenting an image of the innermost of three rings of dusty planet-forming material around the young star called HD141569A. Follow the links to see image 1 and image 2.

We are currently trying to further improve the design and fabrication techniques of these diamond coronagraphs, and are planning to work against the forthcoming Extremely Large Telescope in Chile.

Another ongoing project is to develop a diamond coronagraph to the Breakthrough Initiative. This coronagraph will be used on the Very Large Telescope, operated by European Sothern Observatory, to search for potential habitable planets in our closest star system – Alpha Centauri (click here and here for more information). Such planets could be the targets for an eventual launch of miniature space probes by the Breakthrough Starshot initiative (click here for more information).

(left) Photograph of a K-band diamond AGPM; design wavelength 2.0-2.5 µm. (right) Scanning electron microscope picture of an L-band diamond AGPM; design wavelength 3.4-4.0 µm.

Life science

Early diagnosis of neurodegenerative diseases

We have during the last years been working on the microfabrication of diamond waveguides. The diamond waveguides together with a broadly tunable laser quantum cascade laser (QCL), emitting from 5.5 µm up to 11 µm, are the two key elements in our newly developed label free biosensor based on vibrational spectroscopy. When coupling infrared (IR)-light through the waveguide an evanescent wave will be created at the waveguide surface which will interact with the analyte. Because of the reduced thickness when using waveguides, in combination with using QCL lasers as a light source, an ultra sensitive sensor is expected (compared to ATR-IR spectroscopy, which is an existing technology). Moreover, our waveguide can be functionalized which can be used to bind antibodies to the sensor surface.

The waveguides are fabricated by standard lithographic techniques followed by inductively coupled plasma etching of diamond.  We are also performing simulations of the light propagation in the different types of waveguides. 

In our lab we have a complete optical setup of the biosensor, consisting of a broadly tunable QCL, IR-optics (lenses etc.) for coupling the light into the diamond waveguide, an infrared camera to visualize the IR-beam profile when exiting the diamond waveguide, and a sensitive MCT-detector.

We have demonstrated first measurements on different types of analytes (e.g. isopropanol) at low concentrations (ng) to demonstrate the sensitivity of the sensor. 

Currently we are working on analyzing different forms of the protein alpha-synuclein, which is relevant in understanding the mechanism behind Parkinson’s disease. Recently, we used ATR-IR spectroscopy to analyze the secondary structure of different alpha-synuclein aggregates. Interestingly, it seems to be possible to see the difference in the IR-spectra between the native state and the neurotoxic misfolded state of the protein. Our sensitive diamond waveguide biosensor will be used to analyze the secondary structure of alpha-synuclein at biologically relevant concentrations. Future work includes the functionalization of the diamond waveguide sensor surface to be able to fish out alpha-synuclein from cerebrospinal fluid, with the ultimate goal to detect Parkinson’s disease at an early stage.

This project is performed in collaboration with Prof. Lars Österlund (Solid state physics, Uppsala University), Dr. Per Ola Andersson (Swedish Defence Agency), Assoc. Prof. Fredrik Nikolajeff (Uppsala University) and Assoc. Prof. Joakim Bergström (Molecular Geriatrics, Uppsala University). 

(left) Photograph showing the optical setup of the biosensor, consisting of a broadly tunable QCL, IR-optics and IR-detectors (top right) Schematic showing how a protein of interest can be captured on the diamond waveguide surface; thus making it possible to fish out a protein of interest from a complex mixture. (bottom right) Scanning electron microscope picture of a diamond waveguide end face which is cleaved by focused ion beam milling. The top inset shows a sketch of the free-hanging diamond waveguides on the Si substrate and the bottom inset shows the chip before microfabrication of the diamond waveguides; consisting of a Si substrate with thin films of SiO2 and diamond on top.