Embodiments relate generally to electromagnetic radiation detector devices, systems, and methods using a planar Golay cell. A method for gas detection may comprise providing a gas sealed in a cavity of a gas detector; directing radiative power from a light source through one or more target gases and through a cell body of the gas detector toward the cavity and a wavelength selective absorber of the gas detector, wherein the one or more target gases are located between the light source and the cavity; setting wavelength sensitivity with the wavelength selective absorber, wherein the wavelength sensitivity is irrespective of an angle of incidence (?); absorbing the radiative power by the wavelength selective absorber and by the one or more target gases; detecting, by a pressure sensing element, a pressure change caused by the absorbing of the radiative power; and determining the one or more target gases based on the detected pressure change.