A plasma-based detector using optical spectroscopic techniques for analyzing the constituents of gas samples are provided. The detector includes a plasma-generating mechanism and a plasma-localizing mechanism. Electron-injecting electrodes may be provided in the plasma chamber of the detector. A Pressure control mechanism as well as a doping module may optionally be included. In accordance with some implementations, the collection, detection and analysis of light extracted from the plasma may enable one or more of various operation modes, such as an emission mode, an absorption mode, and indirect detection mode or a constant emission mode.