Microelectromechanical systems (MEMS) based spatial light modulators (SLMs) enclosed in a package filled with a gas to enhance the reliability and lifetime of the SLM, and methods for operating the same in various applications are described. Generally, the SLM includes a number of MEMS modulators, each including a number of light reflective surfaces, at least one light reflective surface coupled to an electrostatically deflectable element suspended above a substrate, and each adapted to reflect and modulate a light beam incident thereon. The package enclosing the SLM includes an optically transparent cover through which the reflective surfaces are exposed to the light beam, and a cavity is filled a low molar mass fill gas having an atomic number of two or less and a thermal conductivity of greater than 100 mW/(m·K). The SLM can include electrostatically deflectable ribbons suspended over a substrate, or a linear array of two-dimensional MEMS modulators.