A simple cell for the analysis of nanoelectromechanical systems under gas pressure. 
A simple yet versatile apparatus for optical microscopy investigations of solid-state devices under high gas pressures is presented.  Interchangeable high-grade sapphire windows with different thicknesses allow variable choice of trade-off between the maximum operating pressure and maximum spatial resolution.  The capabilities of this compact chamber were tested by performing stroboscopic optical interferometry on nanoelectromechanical systems (NEMSs) under capacitive excitation.  With a 1.7 mm thick sapphire window, the cell is safe to operate at pressures ranging from vacuum to 5 MPa.  Minimal optical wavefront distortion allows NEMSs with linear dimensions of 0.1x1.6 microm(2) to be explored.  For a sapphire window with a maximum thickness of 6 mm, the safe operating pressure increases up to an estimated 60 MPa; however, the increasing distortions inhibit signal from NEMSs smaller than approximately 0.5x1 microm(2).  The cell can be used for confocal microscopy, microphotoluminescence and electroluminescence, light scattering spectroscopy, and reflectivity.  The light weight and compact design of the chamber allow mounting on a precision piezomotion control stage or inside a volume tight apparatus such as cryostats.