| 1. |
- Haas, Julian, et al.
(författare)
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Infrared Spectroscopy Based on Broadly Tunable Quantum Cascade Lasers and Polycrystalline Diamond Waveguides
- 2018
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Ingår i: The Analyst. - 0003-2654 .- 1364-5528. ; 143:21, s. 5112-5119
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Tidskriftsartikel (refereegranskat)abstract
- Recently emerging broadly tunable quantum cascade lasers (tQCL) emitting in the mid-infrared (MIR) are a versatile alternative to well established thermal emitters in combination with interferometers as applied in Fourier transform infrared (FTIR) spectroscopy. The wide and highly spectrally resolved wavelength tuning characteristics along with superior spectral energy density renders laser-based vibrational spectroscopy methods an efficient alternative vs. conventional molecular spectroscopies. Using diamond in attenuated total reflection (ATR) sensing formats benefits from the physical robustness and chemical resistivity of the internal reflective element (IRE) material. While inherent material absorption frequently limits the optical path length within diamond ATR elements, the herein presented design combining bright tQCLs with a multi-reflection polycrystalline diamond (PCD) ATR element enables an optical beam path length of approximately 5 cm. Thereby, sensitive spectroscopic measurements in the MIR are enabled. As an example, non-invasive glucose monitoring in human saliva is examined, highlighting the potential benefits of the proposed analytical concept with regards to exquisite sensitivity and selectivity in combination with a robust sensing interface, i.e., diamond. This approach paves the way towards directly analyzing molecular constituents in complex and potentially corrosive biomedical and biochemical matrices.
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| 2. |
- Haas, Julian, et al.
(författare)
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Polycrystalline diamond thin-film waveguides for mid-infrared evanescent field sensors
- 2018
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 3:6, s. 6190-6198
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Tidskriftsartikel (refereegranskat)abstract
- Photonic design and optimization of thin-film polycrystalline diamond waveguides are shown, serving as advanced evanescent field transducers in the mid-infrared fingerprint regime (2000-909 cm(-1); 5-11 mu m). Design constraints inherent to optical/system considerations and the material were implemented in a finite element method (FEM)-based simulation method that allowed three-dimensional modeling of the overall structure. Thus, lateral mode confinement, attenuation in the direction of radiation propagation, and physical resilience were evaluated. In a final step, the designed structures were fabricated, and their utility in combination with a broadly tunable external cavity quantum cascade laser for chemical sensing of a liquid phase analyte was demonstrated.
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| 3. |
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| 4. |
- Piron, Pierre, et al.
(författare)
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Birefringence measurements of diamond space-variant subwavelength gratings
- 2018
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 57:17, s. 4909-4917
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Tidskriftsartikel (refereegranskat)abstract
- Subwavelength gratings are gratings with periods smaller than the incident wavelength. They possess form birefringence, which depends on the grating parameters. This paper presents the results of an experimental method designed to measure the birefringent properties of diamond subwavelength gratings in the mid-infrared. The method consists of monitoring the intensity transmitted through one polarizer, a subwavelength grating, and a second polarizer for various orientations of the first polarizer. By fitting the intensity variation as a function of the orientation of the first polarizer, one can compute the phase shift induced by the grating, its local fast axis orientation, and the ratio of the transverse electric and transverse magnetic transmission efficiencies. The paper describes the method principle and its mathematical model. Then, several numerical simulations of different subwavelength gratings are presented and their results are discussed. Finally, the optical setup is described and the measurements of one subwavelength grating are displayed and compared with the values expected from the manufacturing process.
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| 7. |
- Reggiani, M, et al.
(författare)
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Discovery of a point-like source and a third spiral arm in the transition disk around the Herbig Ae star MWC 758
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 611
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Tidskriftsartikel (refereegranskat)abstract
- Context. Transition disks offer the extraordinary opportunity to look for newly born planets and to investigate the early stages of planet formation. Aims. In this context we observed the Herbig A5 star MWC 758 with the L'-band vector vortex coronagraph installed in the near-infrared camera and spectrograph NIRC2 at the Keck II telescope, with the aim of unveiling the nature of the spiral structure by constraining the presence of planetary companions in the system. Methods. Our high-contrast imaging observations show a bright (Delta L' = 7.0 +/- 0.3 mag) point-like emission south of MWC 758 at a deprojected separation of similar to 20 au (r = 0 ''.111 +/- 0 ''.004) from the central star. We also recover the two spiral arms (southeast and northwest), already imaged by previous studies in polarized light, and discover a third arm to the southwest of the star. No additional companions were detected in the system down to 5 Jupiter masses beyond 0 ''.6 from the star. Results. We propose that the bright L'-band emission could be caused by the presence of an embedded and accreting protoplanet, although the possibility of it being an asymmetric disk feature cannot be excluded. The spiral structure is probably not related to the protoplanet candidate, unless on an inclined and eccentric orbit, and it could be due to one (or more) yet undetected planetary companions at the edge of or outside the spiral pattern. Future observations and additional simulations will be needed to shed light on the true nature of the point-like source and its link with the spiral arms.
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| 8. |
- Vargas Catalan, Ernesto, 1988-
(författare)
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Microfabrication of Optical Components in Synthetic Diamond : Infrared Optics for Applications in Astronomy and Spectroscopy
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Infrared optics is a broad general term, relevant to a range of fields. The manufactured diamond optical components utilized within this thesis were applied to both astronomy, in which direct imaging of star system using large ground-based telescopes and diamond coronagraphs was performed, and in absorption spectroscopy probing solvents and proteins using a tuneable quantum cascade laser and diamond waveguides.The optical components presented in this thesis are all made from diamond, as it is one of few materials that is transparent in the infrared regime. Furthermore, diamond has other unique properties that include high thermal conductivity, low thermal expansion and chemically inertness. In this thesis synthetic diamond grown by chemical vapor deposition has been used, using commercially available components and equipment.The focus of this thesis was to produce optical gratings for different applications using plasma etching. The first steps involved understanding the etch process and optimizing the plasma etch parameters to enable the fabrication of new types of nano/micro meter sized structures in diamond. Optimization of the etch masks is also included in the work. With this newfound knowledge, deeper and narrower optical gratings than before could be realized.Optical evaluation of the gratings in special designed optical test benches was used to determine the coronagraphic performance of the manufactured diamond coronagraphs. Most often the designed etch depth could not be reached in the first attempt and therefore a post-fabrication method for tuning the etch depth was developed. This showed to be vital to realising high performing diamond coronagraphs. Diamond coronagraphs were also installed in several ground based telescopes and discovery of new astronomical objects are presented. With deeper understanding of the etch process more complex coronagraphs in diamond were manufactured opening up for use in the next generation of giant telescopes.In the second part of this thesis, fabrication of diamond waveguides for sensitive analysis of solvents and proteins using infrared spectroscopy is presented. Different designs of diamond waveguides are demonstrated and initial analysis of organic compounds and glucose using a quantum cascade laser as the light source is presented. This type of biosensor will be used to study the secondary structure of proteins relevant for different diseases.
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