Raman Spectroscopy Setup and Characterization

RS measurements were taken in a custom system at Bogazici University Department of Physics. We built the system using three main parts: a diode laser (785 nm, 100 mW, LaserGlow), a spectrometer (QE-Pro, Ocean), and a microscope rigid-body microscope (Nikon Ti). The laser beam was cleaned up with a bandpass filter (Semrock), and the output beam was transmitted through a spatial filter to obtain a single longitudinal mode operation. The cleaned-up beam was sent to the first dichroic mirror (LP805, Thorlabs) and reflected to the other (SP 750, Thorlabs). The reflected beam from the last dichroic mirror was steered to the microscope objective (10×, 0.25 NA, Olympus). The backscattered beam (Rayleigh and Raman photons) was collected via the same light path with 180°C geometry. Finally, the Rayleigh photons were filtered at the first dichroic mirror. The Raman beam was sent to the focusing lens after transmission from a Raman edge filter (Semrock) for further Rayleigh filtering operation. The Raman beam was focused into the multimode fiber (0.22 NA, Thorlabs) using a fiber collimation package (Thorlabs). The coupled beam was sent to the spectrometer, and the spectra were visualized using the appropriate software (Oceanview).