This work presents data concerning the optical nature of the insulated gate field effect transistor (IGFET), how its optical sensitivity relates to its electrical operation, and explores its usefulness as a microluminometer for a chemisensor and biosensor. Although the experiments performed for this dissertation show that the IGFET's light sensitivity does not involve the standard operation of the FET, i.e., the modulation of the source to drain current, they also show that the IGFET's light sensitivity is not a simple photodiode response of the source/base or drain/base junction. This work raises many interesting questions to be answered by future studies concerning the light sensitivity of the IGFET and its possible uses. In this work an instrument was built to probe the IGFET with photons, the IGFET's wavelength response is presented, the detection of recaequorin in a static system is shown to have a limit of detection of 6*10⁻²⁰ moles of recaequorin, and the IGFET is demonstrated as a microluminometer in a FIA system for detecting hypochlorite. The hypochlorite limit of detection is 39 * 10⁻¹² moles.. The author proposes new uses for the IGFET employing its traditional ion sensing role as well as its photosensitivity. Construction of a three dimensional biosensor is suggested. / Ph. D.