A optical phase shifter is provided for adjusting an optical phase of light propagating therethrough along an optical axis. The optical phase shifter includes first and second transparent slides defining a cavity therebetween. A sheet is received in the cavity and has first and second sides. The sheet includes a rigid inner portion alignable with the optical axis and is moveable along the optical axis between a first position and a second position. A tuning structure is operatively engageable with the rigid inner portion of the sheet to selectively move the rigid inner portion of the sheet along the optical axis so as to adjust the optical phase of light propagating through the optical phase shifter.