Journal: Scientific Reports

Article Title: Digital holographic microscopy for real-time observation of surface-relief grating formation on azobenzene-containing films

doi: 10.1038/s41598-020-76573-6

Figure Lengend Snippet: Optical measurement setup for simultaneous surface height measurement and SRG patterning. ( a ) Schematic of the optical components used to project the interference pattern for SRG writing through the digital holographic microscope. The light input (488 nm) to the microscope is through a polarization maintaining fibre, output of which is collimated by lenses L2. After adjusting the polarization states with quarter- and half-wave plates (QWP and HWP, respectively), the two beams are combined with a 50:50 beam splitter BS2. The combined beam is then focused onto the back focal plane of the microscope objective by lens L1, resulting in two collimated beams exiting the objective. The angles of these two beams are controlled by the XY mounts for the ends of the optical fibre. ( b ) DHM and AFM images of an SRG with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$4\ \upmu \hbox {m}$$\end{document} 4 μ m period inscribed with the optical setup shown in ( a ) using left- and right-handed circular polarizations for the inscription. The grating cross sections are compared in ( c ), with the DHM measurement shown in orange color and the AFM measurement in blue.

Article Snippet: We use a 488 nm optically pumped semiconductor laser (Coherent Genesis CX-488 2000) that is coupled into a one-to-two beam splitting, polarization maintaining, single mode optical fibre (Thorlabs PN480R5F1).

Techniques: Microscopy

Journal: Scientific Reports

Article Title: Digital holographic microscopy for real-time observation of surface-relief grating formation on azobenzene-containing films

doi: 10.1038/s41598-020-76573-6

Figure Lengend Snippet: ( a ) Feedback camera (CAM2) images for intensity (top) and polarization (bottom) interference patterns. The resulting grating period on the sample plane is \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$4\ \upmu \hbox {m}$$\end{document} 4 μ m . The polarization interference pattern becomes visible due to a slight imbalance in the laser power of the two interfering beams, enabling the active feedback based on the camera signal for both types of patterns. ( b ) Relative error (compared to the grating period) in the grating position over time with (blue) and without (orange) active feedback enabled. ( c ) Histogram for the error in the grating positioning over 27 min with the active feedback enabled.

Article Snippet: We use a 488 nm optically pumped semiconductor laser (Coherent Genesis CX-488 2000) that is coupled into a one-to-two beam splitting, polarization maintaining, single mode optical fibre (Thorlabs PN480R5F1).

Techniques:

Journal: Scientific Reports

Article Title: Digital holographic microscopy for real-time observation of surface-relief grating formation on azobenzene-containing films

doi: 10.1038/s41598-020-76573-6

Figure Lengend Snippet: SRG inscription as captured by the DHM. In ( a – d ) 2D height maps of a \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$4\ \upmu \hbox {m}$$\end{document} 4 μ m period grating written utilizing left- and right-handed circular polarizations for the writing beams. The red scale bars in the figures correspond to a \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10\ \upmu \hbox {m}$$\end{document} 10 μ m distance. The 2D height maps are captured at a 200 fps frame rate, with single measurements at 0.0 s, 0.5 s, 1.0 s, and 3.0 s after opening the shutter for the writing beams shown in ( a – d ), respectively. In ( e ) the grating heights are shown for L/R and S/S polarizations for the writing beams with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2\ \hbox {W}/\hbox {cm}^2$$\end{document} 2 W / cm 2 average intensity, showing fast SRG inscription for the L/R polarization, but only minor surface deformation for the S/S polarization combination, as expected.

Article Snippet: We use a 488 nm optically pumped semiconductor laser (Coherent Genesis CX-488 2000) that is coupled into a one-to-two beam splitting, polarization maintaining, single mode optical fibre (Thorlabs PN480R5F1).

Techniques:

Journal: Scientific Reports

Article Title: Digital holographic microscopy for real-time observation of surface-relief grating formation on azobenzene-containing films

doi: 10.1038/s41598-020-76573-6

Figure Lengend Snippet: Effects from phase grating formation in DR1g films on the observed grating heights. In ( a ) the grating is written with P-polarized amplitude interference pattern, while in ( b ) a polarization interference pattern created with + 45/− 45 linearly polarized beams is used. The 675 nm and 794 nm labels refer to the probe wavelength used in the DHM, with the probe polarizations being close to P and S polarizations for 675 nm and 794 nm, respectively. The polarization directions for the interfering beams are depicted with arrows in ( c ), with the length of the lines illustrating the intensity distribution for the P/P pattern. The resulting grating profiles are shown schematically, with the color corresponding to the change in the refractive index due to the reorientation of the azobenzene molecules inside the film for S-polarized probe beam. For a P-polarized probe beam the change in the refractive index is in the opposite direction, i.e. the color scale is reversed.

Article Snippet: We use a 488 nm optically pumped semiconductor laser (Coherent Genesis CX-488 2000) that is coupled into a one-to-two beam splitting, polarization maintaining, single mode optical fibre (Thorlabs PN480R5F1).

Techniques: Refractive Index