The liquid crystal variable phase retarder is a transmissive element with an electrically tunable optical phase retardance. The phase retardance can be tuned from 0 to sevral micormeters with a simple applied bias (0-5V). The device can be used from 400nm to 1800nm. Intensity losses are not higher than 15%. Optionnaly the phase retarder can be provided with a special dedicated USB electrical driver. Alternativly the phase retarder can also be used as optical valve (for a narrow wavelength range) or as polarization state controller.