RESUMEN
We have experimentally demonstrated spatially selective absorption in Ag-SiO2-Ag based trilayer thin films by tuning the deposition angle of SiO2layer. These structures generate cavity resonance which can be tuned across the substrate locations due to spatially selective thickness and refractive index of silicon oxide (SiO2) film sandwiched between metallic silver (Ag) mirrors. Spatially selective property of SiO2film is obtained by oblique angle deposition technique using an electron beam evaporation system. The resonance wavelength of absorption in this trilayer structure shifts across the substrate locations along the direction of oblique deposition. The extent of shift in resonance increases with increase in angle of deposition of SiO2layer. 4.14 nm mm-1average shift of resonance wavelength is observed when SiO2is deposited at 40° whereas 4.76 nm mm-1average shift is observed when SiO2is deposited at 60°. We observed that the width of resonance increases with angle of deposition of the cavity layer and ultimately the resonant absorption disappears and becomes broadband when SiO2is deposited at glancing angle deposition (GLAD) configuration. Our study reveals that there is a suitable range of oblique angle of deposition from 40° to 60° for higher spatial tunability and resonant absorption whereas the absorption becomes broadband for glancing angle deposition.
RESUMEN
Water is one of the most abundant molecules on the earth and its isotopic composition measurements find application in various fields. Even though it is an extensively studied molecule, many absorption lines of its isotopologues are still unknown. In the recent years, a significantly improved sensitivity of spectroscopic methods has brought forth a scope of studying the weak and extremely challenging molecular transitions. The paper describes an off axis integrated cavity output spectroscopic investigation the deuterated water isotopologues, viz. HD16O, HD17O and HD18O, in the 7178-7196 cm-1 spectral region. A few new ro-vibrational transitions of HD18O are reported along with their line strengths and assignments. Apart from this, observation of extremely weak transitions of deuterated water isotopologues and comparison with existing database and published data is also presented. The present study will find application in field of accurate and sensitive HD16O, HD17O and HD18O detections.