Mikael Karlsson

Recovery of titanium dioxide and other pigments from waste paint by pyrolysis

In this work, a model paint containing several types of inorganic pigments was pyrolyzed in a microwave-heated unit. The goal of the pyrolysis process was to recover and recycle the inorganic components in the paint, most importantly titanium dioxide (TiO2). The solid residue remaining after pyrolysis was further heat treated in air to remove most of the char in the TiO2-containing product. The recovered TiO2-containing product was used in two types of paint formulation as a replacement for virgin pigments. The properties of the paints containing recycled TiO2 pigment and extenders were evaluated and compared with a standard paint formulation containing only virgin TiO2 pigment and virgin extenders. A reduction in paint whiteness was observed but the opacity, gloss, and durability were nearly equivalent to that of the standard paint. Another consequence of using recycled pigments was that the recycled mix of TiO2 pigments and extenders was harder to disperse in the paint than the mix based on virgin materials, thus giving the painted surface a somewhat rough texture. The recycled material has shown promising results as a pigment/extender but further work is needed to optimize the recycled product to meet whiteness and dispersion requirements for incorporation in paint formulations on an industrial scale.

Diamond micro-optics for high-power lasers

We have developed a method for fabricating any type of optical surfaces in diamond. The method consists of the following steps: First, a polymer film, spun onto diamond substrates of optical quality, is patterned by lithographic processes. Next, the surface relief is transferred into the underlying diamond by use of inductively coupled plasma dry etching in an oxygen/argon chemistry. Using this technique, we have successfully demonstrated the fabrication of diamond spherical microlenses, blazed gratings, Fresnel lenses, subwavelength gratings and diffractive beam-shaping elements. The spherical microlenses had apertures of 100 µm and f-number of 3.7. The phase error, measured with a Twyman-Green interferometer at 633 nm, was found to be less than 31 nm. The RMS value of the surface roughness over the spherical surface was measured to be 6 nm. The diffraction efficiency for the blazed grating was measured to be 68% at 400 nm, with a theoretical maximum of 71%. The subwavelength grating was designed for reducing surface reflections at a wavelength of 10.6 µm. Photospectrometric results show that the optical transmission was increased from 70%, using a non-structured diamond substrate, to 81%, using our subwavelength structured diamond. The transmission can be further increased by structuring both sides of the substrate. Finally, the beam-shaping element has been tested with a 6kW carbon-dioxide laser, to microstructure pieces of PMMA. The results are excellent, showing diffraction limited spots.We have developed a method for fabricating any type of optical surfaces in diamond. The method consists of the following steps: First, a polymer film, spun onto diamond substrates of optical quality, is patterned by lithographic processes. Next, the surface relief is transferred into the underlying diamond by use of inductively coupled plasma dry etching in an oxygen/argon chemistry. Using this technique, we have successfully demonstrated the fabrication of diamond spherical microlenses, blazed gratings, Fresnel lenses, subwavelength gratings and diffractive beam-shaping elements. The spherical microlenses had apertures of 100 µm and f-number of 3.7. The phase error, measured with a Twyman-Green interferometer at 633 nm, was found to be less than 31 nm. The RMS value of the surface roughness over the spherical surface was measured to be 6 nm. The diffraction efficiency for the blazed grating was measured to...

Fabrication of refractive and diffractive micro-optical structures in diamond

Fabrication of refractive microlenses, blazed gratings and diffractive Fresnel lenses in diamond is demonstrated. In the fabrication process we have used photolithography, electron-beam lithography and plasma etching. The micro-optical elements have been optically evaluated.

Development of a diamond waveguide sensor for sensitive protein analysis using IR quantum cascade lasers

Microfabricated diamond waveguides, between 5 and 20 μm thick, manufactured by chemical vapor deposition of diamond, followed by standard lithographic techniques and inductively coupled plasma etching of diamond, are used as bio-chemical sensors in the mid infrared domain: 5-11 μm. Infrared light, emitted from a broadly tunable quantum cascade laser with a wavelength resolution smaller than 20 nm, is coupled through the diamond waveguides for attenuated total reflection spectroscopy. The expected advantages of these waveguides are a high sensitivity due to the high number of internal reflections along the propagation direction, a high transmittance in the mid-IR domain, the bio-compatibility of diamond and the possibility of functionalizing the surface layer. The sensor will be used for analyzing different forms of proteins such as α-synuclein which is relevant in understanding the mechanism behind Parkinsons disease. The fabrication process of the waveguide, its characteristics and several geometries are introduced. The optical setup of the biosensor is described and our first measurements on two analytes to demonstrate the principle of the sensing method will be presented. Future use of this sensor includes the functionalization of the diamond waveguide sensor surface to be able to fish out alpha-synuclein from cerebrospinal fluid.

Polarization analysis of diamond subwavelength gratings acting as space-variant birefringent elements

Subwavelength gratings are gratings with a period smaller than the incident wavelength. They only allow the zeroth order of diffraction, they possess form birefringence and they can be modeled as birefringent plates. In this paper, we present the first results of an experimental method designed to measure their polarization properties. The method consists in measuring the variation of the light transmitted through two linear polarizers with the subwavelength component between them for several orientations of the polarizers. In this paper, the basic principles of the method are introduced and the experimental setup is presented. Several types of components are numerically studied and the optical measurements of one component are presented.

Around the world: status and prospects with the infrared vortex coronagraph (Conference Presentation)

Since its first light at the VLT in 2012, the Annular Groove Phase Mask (AGPM) has been used to implement vortex coronagraphy into AO-assisted infrared cameras at two additional world-leading observatories: the Keck Observatory and the LBT. In this paper, we review the status of these endeavors, and briefly highlight the main scientific results obtained so far. We explore the performance of the AGPM vortex coronagraph as a function of instrumental constraints, and identify the main limitations to the sensitivity to faint, off-axis companions in high-contrast imaging. These limitations include the AGPM itself, non-common path aberrations, as well as the data processing pipeline; we briefly describe our on-going efforts to further improve these various aspects. Based on the lessons learned from the first five years of on-sky exploitation of the AGPM, we are now preparing its implementation in a new generation of high-contrast imaging instruments. We detail the specificities of these instruments, and how they will enable the full potential of vortex coronagraphy to be unleashed in the future. In particular, we explain how the AGPM will be used to hunt for planets in the habitable zone of alpha Centauri A and B with a refurbished, AO-assisted version of the VISIR mid-infrared camera at the VLT (aka the NEAR project), and how this project paves the way towards mid-infrared coronagraphy on the ELT with the METIS instrument. We also discuss future LM-band applications of the AGPM with VLT/ERIS, ELT/METIS, and with a proposed upgrade of Keck/NIRC2, as well as future applications at shorter wavelengths, such as a possible upgrade of VLT/SPHERE with a K-band AGPM.

High contrast imaging for the enhanced resolution imager and spectrometer (ERIS)

ERIS is a diffraction limited thermal infrared imager and spectrograph for the Very Large Telescope UT4. One of the science cases for ERIS is the detection and characterization of circumstellar structures and exoplanets around bright stars that are typically much fainter than the stellar diffraction halo. Enhanced sensitivity is provided through the combination of (i) suppression of the diffraction halo of the target star using coronagraphs, and (ii) removal of any residual diffraction structure through focal plane wavefront sensing and subsequent active correction. In this paper we present the two coronagraphs used for diffraction suppression and enabling high contrast imaging in ERIS.

NEAR: New Earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)

By adding a dedicated coronagraph, ESO in collaboration with the Breakthrough Initiatives, modifies the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability this instru- ment has. After the VISIR upgrade in 2012, where coronagraphic masks were first added to VISIR, it became evident that coronagraphy at a ground-based 8m-class telescope critically needs adaptive optics, even at wavelengths as long as 10μm. For VISIR, a work-horse observatory facility instrument in normal operations, this is ”easiest” achieved by bringing VISIR as a visiting instrument to the ESO-VLT-UT4 having an adaptive M2. This “visit” enables a meaningful search for Earth-like planets in the habitable zone around both α-Cen1,2. Meaningful here means, achieving a contrast of ≈ 10-6 within ≈ 0.8arcsec from the star while maintaining basically the normal sensitivity of VISIR. This should allow to detect a planet twice the diameter of Earth. Key components will be a diffractive coronagraphic mask, the annular groove phase mask (AGPM), optimized for the most sensitive spectral band-pass in the N-band, complemented by a sophisticated apodizer at the level of the Lyot stop. For VISIR noise filtering based on fast chopping is required. A novel internal chopper system will be integrated into the cryostat. This chopper is based on the standard technique from early radio astronomy, conceived by the microwave pioneer Robert Dicke in 1946, which was instrumental for the discovery of the 3K radio background.

Design and performance simulations of mid-IR AGPMs for ELT/METIS applications

The subwavelength grating vortex coronagraph (SGVC) is a focal-planespiral-like phase mask whose key benefit is to allow high contrast imaging atsmall angles. Directly etched onto a CVD diamond substrate, it is well suitedto perform in the mid-infrared domain. It provides a continuous helicalphase ramp with a dark singularity in its center, and is characterized by itsnumber of phase revolutions, called the topological charge. Over the pasttwo years, we have manufactured several charge-2 SGVCs (a.k.a. annulargroove phase masks) and successfully demonstrated their performanceson 10-m class telescopes (LBT, VLT/NaCo, VLT/VISIR). To prevent stellarleakage on future 30-m class telescopes (E-ELT, TMT, GMT), a broaderoff-axis extinction is required, which can be achieved by increasing thetopological charge. We have recently proposed an original design for acharge-4 SGVC allowing less starlight to leak through the coronagraph, atthe cost of a degraded inner working angle. In this talk, we report on ourlatest development of higher charge SGVCs. From 3D rigorous numericalsimulations using a finite-difference time-domain (FDTD) algorithm, weConference 9605: Techniques and Instrumentationfor Detection of Exoplanets VIIR eturn to Contents +1 360 676 3290 · help@spie.org 647have derived a family of coronagraphs with higher topological charge(SGVC4/6/8). Our new optimization method addresses the principallimitation of such space-variant polarization state manipulation, i.e., theinconvenient discontinuities in the discrete grating pattern. The resultinggratings offer improved precision to the phase modulation compared toprevious designs. Finally, we present our preliminary manufacturing andmetrology results for infrared components down to the K-band.In this talk, we will review the on-going activities within the VORTEX teamat the University of Liege and Uppsala University. The VORTEX project aimsto design, manufacture, test, and exploit vector ...The direct detection of exoplanets requires the use of dedicated, highcontrast imaging instruments. In this context, vector vortex coronagraphs(VVCs) are considered to be among the most promising solutions to reachhigh contrast at small angular separations. They feature a small innerworking angle (down to 0.9 lambda/D), high throughput, clear off-axis360° discovery space, and are simple to implement. The AGPM (AnnularGroove Phase Mask) is an implementation of the vortex phase mask, whichprovides achromaticity over an appreciable spectral range thanks to the useof sub-wavelength gratings. The grating profile can be optimized based onthe rigorous coupled wave analysis (RCWA) to achieve a quasi-achromaticphase shift up to a very broad band (L+M band: 3.5-5.1μm). These deviceshave been manufactured onto CVD diamond substrates, using reactiveion etching. In this communication, I will first present the latest RCWAConference 9605: Techniques and Instrumentationfor Detection of Exoplanets VIIR eturn to Contents +1 360 676 3290 · help@spie.org 631simulations performed in the L, M and N spectral bands, and for somecombinations of these bands. The resulting optimized AGPMs could beperfectly integrated in the E-ELT/METIS instrument, which aims at detectingand characterizing exoplanets by direct imaging. The target contrast forMETIS is <1e-4 at 2 lambda/D (~40 mas in L band), which translates into apeak rejection rate of few hundreds for the AGPMs. Secondly, the opticalpropagation within the METIS instrument will be studied to determine theperformances of a vortex coronagraph at the focus of METIS. In particular,the effect of the central obstruction, spiders, missing E-ELT segments,and pointing jitter will be analysed, together with the sensitivity to tip-tilt.Finally, the atmosphere and the AO contributions will be considered toobtain more realistic results.

A family of subwavelength grating vortexcoronagraphs (SGVCs) with higher topological charge

The subwavelength grating vortex coronagraph (SGVC) is a focal-planespiral-like phase mask whose key benefit is to allow high contrast imaging atsmall angles. Directly etched onto a CVD diamond substrate, it is well suitedto perform in the mid-infrared domain. It provides a continuous helicalphase ramp with a dark singularity in its center, and is characterized by itsnumber of phase revolutions, called the topological charge. Over the pasttwo years, we have manufactured several charge-2 SGVCs (a.k.a. annulargroove phase masks) and successfully demonstrated their performanceson 10-m class telescopes (LBT, VLT/NaCo, VLT/VISIR). To prevent stellarleakage on future 30-m class telescopes (E-ELT, TMT, GMT), a broaderoff-axis extinction is required, which can be achieved by increasing thetopological charge. We have recently proposed an original design for acharge-4 SGVC allowing less starlight to leak through the coronagraph, atthe cost of a degraded inner working angle. In this talk, we report on ourlatest development of higher charge SGVCs. From 3D rigorous numericalsimulations using a finite-difference time-domain (FDTD) algorithm, weConference 9605: Techniques and Instrumentationfor Detection of Exoplanets VIIR eturn to Contents +1 360 676 3290 · help@spie.org 647have derived a family of coronagraphs with higher topological charge(SGVC4/6/8). Our new optimization method addresses the principallimitation of such space-variant polarization state manipulation, i.e., theinconvenient discontinuities in the discrete grating pattern. The resultinggratings offer improved precision to the phase modulation compared toprevious designs. Finally, we present our preliminary manufacturing andmetrology results for infrared components down to the K-band.In this talk, we will review the on-going activities within the VORTEX teamat the University of Liege and Uppsala University. The VORTEX project aimsto design, manufacture, test, and exploit vector ...The direct detection of exoplanets requires the use of dedicated, highcontrast imaging instruments. In this context, vector vortex coronagraphs(VVCs) are considered to be among the most promising solutions to reachhigh contrast at small angular separations. They feature a small innerworking angle (down to 0.9 lambda/D), high throughput, clear off-axis360° discovery space, and are simple to implement. The AGPM (AnnularGroove Phase Mask) is an implementation of the vortex phase mask, whichprovides achromaticity over an appreciable spectral range thanks to the useof sub-wavelength gratings. The grating profile can be optimized based onthe rigorous coupled wave analysis (RCWA) to achieve a quasi-achromaticphase shift up to a very broad band (L+M band: 3.5-5.1μm). These deviceshave been manufactured onto CVD diamond substrates, using reactiveion etching. In this communication, I will first present the latest RCWAConference 9605: Techniques and Instrumentationfor Detection of Exoplanets VIIR eturn to Contents +1 360 676 3290 · help@spie.org 631simulations performed in the L, M and N spectral bands, and for somecombinations of these bands. The resulting optimized AGPMs could beperfectly integrated in the E-ELT/METIS instrument, which aims at detectingand characterizing exoplanets by direct imaging. The target contrast forMETIS is <1e-4 at 2 lambda/D (~40 mas in L band), which translates into apeak rejection rate of few hundreds for the AGPMs. Secondly, the opticalpropagation within the METIS instrument will be studied to determine theperformances of a vortex coronagraph at the focus of METIS. In particular,the effect of the central obstruction, spiders, missing E-ELT segments,and pointing jitter will be analysed, together with the sensitivity to tip-tilt.Finally, the atmosphere and the AO contributions will be considered toobtain more realistic results.