Abstract: A spectrum analyzer for analyzing electromagnetic radiation which may be utilized to determine the radiation wavelength and power. The analyzer includes a gas filled chamber which has a collimating lens through which radiation is injected, and a reflective plate that reflects the radiation back toward the lens. A standing wave is created within the chamber having spatially periodic peaks. The chamber gas pressure is regulated to a pressure such that gas breakdown occurs, thereby generating a light pattern at each standing wave peak. The patterns are then photographed, and the patterns' diameters and spacing are measured from the resulting photograph. From the spacing and diameter obtained, wavelength and power may be calculated.