Abstract: A cavity thickness compensated etalon filter. A tuning medium is placed in a Fabry-Perot etalon cavity. The index of refraction of the tuning medium varies as a function of voltage applied across the medium. The etalon is formed of two generally flat substrates disposed substantially parallel to one another. Each substrate has a layer of conductive material within the cavity adjacent the substrate. Each substrate also has a layer of reflective material within the cavity adjacent the substrate. At least one layer of reflective material is only partially reflective so as to enable light to pass into and out of the cavity. Liquid crystal material may be used as a tuning medium in the cavity. In the case of liquid crystal material, the etalon also comprises an alignment layer disposed within the cavity adjacent each substrate to pre-order the liquid crystal material.

Abstract: A fixture for angularly aligning an optical device. A monolithic structure is provided having a first adjustment member for holding an optical device and tilting the device in one direction, a second adjustment member attached to the first adjustment member for tilting the optical device in a direction orthogonal to the direction of tilt provided by the first adjustment member, and a base for holding the first and second adjustment members. The first adjustment member is attached to the second adjustment member by a flexible connection having a tilt axis in a first lateral direction and the second adjustment member is attached to the base by a connection having a tilt axis in a lateral direction orthogonal to the lateral direction of the first connection.

Abstract: A fast response liquid crystal optical retarder system. A liquid crystal retarder system employs one or more liquid crystal cells and corresponding drive circuits. The drive circuits provide to the cell a rectangular wave ac voltage signal whose RMS voltage is controlled. To switch from one retardance to another, the voltage is increased or decreased beyond the voltage corresponding to the target retardance and then, prior to or when the target retardance is reached, the applied voltage is switched to the voltage corresponding to the target retardance. One or more pairs of liquid crystal cells provided sequentially along the path of light propagation and with their eigen-axis orthogonal to one another to increase or decrease the total retardance rapidly. The retarder system is incorporated in a polarization control system and in a fiber-optic link.

Abstract: A method for on-wafer testing of microwave devices, such as photodiodes, including a biasing method applicable when the device has a lower end connected to the ground plane of the wafer. Elements having a diode-like characteristic, such as photodiodes, are arranged side-by-side with the device, each preferably being of like geometry with the device, and each having an end connected to the ground plane. A first voltage is applied between the ground conductors of the probe and the ground plane of the wafer to place each element in forward-biased condition thereby creating a return path for the lower end of the device to the ground conductors located on the upper side of the wafer.

Abstract: A fiber optic wafer probe, for use in measuring the parameters of photodetectors and other optoelectronic test devices at the wafer level, has a probe body along which an optical fiber extends to protrude from a tip of the probe body. The probe body loosely guides the optical fiber so that at least a significant portion of the length of the optical fiber is movable longitudinally with respect to the tip and probe body. This provides protection against excessive contact force between the fiber and the test device by enabling the optical fiber to buckle longitudinally in response to longitudinal overtravel of the fiber toward the test device. The probe body is of elongate shape with a probe tip at one end and a connector at the other end for detachably connecting the optical fiber to the probe body.

Abstract: A polarization insensitive optical attenuator (10,40) uses a polymer-dispersed liquid crystal (PDLC) film (14,56) to provide attenuation control over a wide range of attenuation values. The attenuator has a relatively low minimum attenuation and reliable light transmission with minimal insertion loss. The present invention is also adaptable for use with a temperature controller (200) that stabilizes the PDLC film, which promotes more uniform, predictable attenuation values.