Low-Cost Raman Spectroscopy using a Violet Diode Laser

New generations of diode lasers that emit violet light make possible the assembly of a low-cost Raman spectrometer for use in the student laboratory. Because Raman scattering intensity is inversely proportional to the fourth power of the wavelength of the incident radiation, the use of these violet lasers has advantages over their longer-wavelength counterparts. The higher scattering efficiencies permit the use of a relatively inexpensive PC-based spectrometer (e. g. , an Ocean Optics spectrometer) for wavelength analysis of the scattered radiation. Combined with a notch filter and several lenses, the violet diode laser and spectrometer permit the construction of an instrument at a total cost of around 6500, including the PC-based spectrometer. This cost will decrease dramatically in the near future as violet diode lasers are commercialized for data storage applications. Performance of the instrument is demonstrated on carbon tetrachloride, water, and benzene. These experiments show Stokes radiation bands in agreement with published data. While the use of the notch filter and limited resolution of the spectrometer obscure some bands, the instrument serves to illustrate fundamental principles of Raman spectroscopy appropriate for physical and analytical chemistry teaching laboratories.