Abstract: A laser radiation detection system is disclosed comprising phase retarding apparatus for retarding a portion of the laser radiation incident on the system, optical focusing apparatus, detector apparatus and an electrical circuit. The optical focusing apparatus focuses the incident radiation on the detector apparatus. The detector apparatus is located in the focal plane and detects the presence of laser radiation due to the uneven distribution of light caused by the interference of the retarded portion of the incident radiation with the portion that remains in phase. The detector apparatus supplies output signals in response to the incident radiation received by each detector to the electrical circuit which then compares the various outputs from the detector apparatus in pairs and outputs a signal indicating the presence of laser radiation when the sum of the differences of the detector outputs is greater than a predetermined threshold value.

Abstract: An optical imaging device includes an optical device comprising means for absorbing at least one wavelength of light incident thereupon, a first layer of a first material having a first index of refraction and being in thermal contact with the absorbing means, and a second layer of a second material having a second index of refraction which is larger than the first index of refraction and which forms an interface with the first layer. The first layer is placed between the absorbing means and the second layer. The phase, amplitude or both phase and amplitude of the reflected light can be modulated by thermally induced changes in the first index of refraction. A method of modulating a first optical beam with a second optical beam is also provided.