All the Raman spectra, PL spectra, and the spatial maps of Raman and PL were acquired with a laser excitation of 488 nm (2.54 eV) and recorded using a commercial system (WITec, alpha300 RA) where the laser was delivered through a single-mode optical fiber and an upright microscope using a 100× working distance objective with 0.9 NA (numeric aperture). The typical incident laser power on a sample was maintained at approximately 100 μW, while the typical acquisition times ranged from 0.05 to 0.2 s.

Some PL spectra in the Supplementary Materials were measured in a custom-built micro-PL setup. The PL was excited with a continuous wave diode-pumped solid-state laser [532 nm (2.33 eV), 100 mW; Excelsior, Spectra-Physics] through an upright microscope using a 100× working distance objective with 0.9 NA (beam spot, ~1 μm). The PL light was analyzed by a spectrometer (f = 0.3 m; SpectraPro 2300i, Acton) that was coupled to the microscope and equipped with 150, 600, and 1800 grooves/mm gratings and a charge-coupled device (CCD) camera (PIXIS: 256BR, Princeton Instruments). The typical acquisition times were varied from 0.5 to 5 s depending on the PL intensity.

SHG measurements were conducted using a 40-fs Ti:Sapphire laser (Micra, Coherent) at 800 nm and an 80-MHz repetition rate. The laser beam was passed through a half-wave plate mounted in a rotation stage and was directed into an upright microscope (Olympus) and focused onto a sample surface using a 100× microscope objective (0.9 NA) to a ~1-μm spot. The laser energy at the sample surface was ~0.1 mW. The SHG light was collected in backscattering configuration using the same objective and was directed to a monochromator (f = 0.3 m; SpectraPro 2300i, Acton) that was coupled to the microscope and equipped with a 150-grooves/mm grating and a CCD camera (PIXIS: 256BR, Princeton Instruments). Before entering the monochromator, the SHG light was passed through a short-pass cutoff filter (650 nm) and a polarizer to filter out the fundamental excitation light at 800 nm and select the SHG polarization parallel to that of the excitation light.

Note: The content above has been extracted from a research article, so it may not display correctly.



Q&A
Please log in to submit your questions online.
Your question will be posted on the Bio-101 website. We will send your questions to the authors of this protocol and Bio-protocol community members who are experienced with this method. you will be informed using the email address associated with your Bio-protocol account.



We use cookies on this site to enhance your user experience. By using our website, you are agreeing to allow the storage of cookies on your computer.