The present invention relates to a light-emitting diode (LED) lighting fixture, which comprises a radiator, a housing and an LED module mounted at the bottom of the radiator, and further comprises a lamp holder being fixed on the top of the radiator and running through the housing, an elastic element clamped between the lamp holder and the housing, and a lamp shade encircling the LED module. The radiator includes a chassis, a body extended upwards from the chassis, and a plurality of radiating fins; one side of the radiator close to the bottom is provided with a recess.

Disclosed herein is an optical diffuser including a compressible, elastic polymeric bulk having an exterior portion for diffusion of light received from a light emitting surface, a planar mounting surface configured to seal against light emitting surface, and an atmospheric gas-filled cavity within bulk, cavity terminating at an opening within planar mounting surface, cavity has a first volume when bulk is at rest and a second, reduced volume when bulk is compressed, such that when planar mounting surface is placed in full engagement with light emitting surface so as to form a planar contact interface therewith, application of a momentary inward compressive force of the elastic polymeric bulk expels gas from within the cavity, and subsequent removal of the compressive force facilitates elastic recovery of bulk, thereby to give rise to a partial vacuum within cavity, and causing optical diffuser to adhere to light emitting surface under a suction force.