title: Diamonds are a spectroscopist's best friend: thin-film diamond mid-infrared waveguides for advanced chemical sensors/biosensors.
abstract: The first combination of mid-infrared (MIR) tunable quantum cascade lasers (tQCLs) with thin-film diamond strip waveguides (DSWGs) suitable for advanced chemical sensing/biosensing is demonstrated. The sensing system is composed of thin diamond films grown on surface-passivated Si wafers via chemical vapor deposition (CVD) and microstructured using inductively coupled plasma (ICP) etching, serving as photonic waveguides for radiation emitted by a broadly tunable quantum cascade laser (tQCL) in the spectral regime of 5.78-6.35 μm (1570-1730 cm(-1)). The characterization of the free-standing diamond waveguides reveals excellent transmission properties across a broad MIR band. As a proof of concept, the detection of acetone in D2O via evanescent field absorption is demonstrated achieving a limit of detection (LOD) as low as 200 pL, which indicates a significant sensitivity improvement compared to conventional MIR slab/strip waveguides reported to date. Providing characteristic absorption features within the tuning range of the tQCL, studies using anisaldehyde as an analyte further corroborate the potential of tQCL-DSWG-based chemical sensors/biosensors.
authors.affiliation: Institute of Analytical and Bioanalytical Chemistry, University of Ulm , Albert-Einstein-Allee 11, 89075 Ulm, Germany.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Wang
authors.forename: Mikael
authors.initials: M
authors.lastname: Karlsson
authors.forename: Pontus
authors.initials: P
authors.lastname: Forsberg
authors.forename: Markus
authors.initials: M
authors.lastname: Sieger
authors.forename: Fredrik
authors.initials: F
authors.lastname: Nikolajeff
authors.forename: Lars
authors.initials: L
authors.lastname: Österlund
authors.forename: Boris
authors.initials: B
authors.lastname: Mizaikoff
mesh_terms: D000096:Acetone / Q000032:analysis; D001547:Benzaldehydes / Q000032:analysis; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods; D018130:Diamond / Q000737:chemistry*; D004867:Equipment Design; D007259:Infrared Rays; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation* / Q000379:methods
chemical_list: D001547:Benzaldehydes; D000096:Acetone; D018130:Diamond; C024896:4-anisaldehyde