I would like to specify the ultraviolet in order to get a specific wavelength. Now, I use ultraviolet lamp with wavelength from 300-400 nm. I want to make the wavelength more narrow and then use the specific wavelength (i.e. 315-330 nm or 380-400 nm) for irradiation purpose. Does anyone know how to achieve it? I consider to use glass filter but I have no idea where I can get the precise light filter.