Abstract: An integrating hydrophone sensing element is provided having improved sensitivity and capability of withstanding high pressures. The sensing element consists of a rigid cylinder with semicylindrical sensing surfaces rigidly connected to the cylinder at diametrically-opposite points. A membrane of piezoelectric polymer material extends diametrically across the cylinder and is attached to the cylinder at points displaced 90.degree. from the connections of the sensing surfaces. Vibration of the cylinder by acoustic signals transmitted from the sensing surfaces causes vibration of the membrane and produces an electrical output signal.

Abstract: Protection of microwave antennas from incident irradiation from high power lasers is accomplished by placing a protective covering or radome over antenna elements to be protected. The radome is constructed such that it is substantially transparent to electromagnetic radiation in the microwave frequency range and at the same time substantially opaque to electromagnetic radiation in the laser frequency range. The radome is constructed of multilayers of a refractory ceramic material, such as boron nitride and beryllium oxide, spaced apart with the spaces evacuated. When the electromagnetic radiation from a high power laser strikes the radome of this invention, the opaqueness to the laser energy causes a conversion to heat energy which is then insulated from sensitive antenna elements by the evacuated spaces separating the refractory ceramic layers.