Designer spectrographs for applications in the advanced undergraduate instructional lab

Abstract

In an advanced undergraduate instructional laboratory, it is often necessary to analyze the spectrum of light emitted from an experimental setup. There are numerous instruments that are used to accomplish this analysis, including spectrometers and spectrographs. In this report, we present 3D-printed, low-budget spectrographs (∼ US $200), which are specifically designed for different applications. For example, one can either observe a visible spectrum over a large range of wavelengths about a desired center wavelength or achieve more precise measurements by choosing a smaller part of the visible spectrum. Our generalized design approach is well within the knowledge base of advanced undergraduate physics majors and can be applied to a wide range of applications within the visible spectrum. To demonstrate the utility of these designer spectrographs, we provide examples of recording multiple doublets in the sodium spectrum (a determination of the fine structure spin-orbit splitting of the 3p energy level) as well as measuring the wavelength differences between the hydrogen and deuterium Balmer alpha lines (a measurement of an isotope shift).