Abstract: Antenna structures are provided which facilitate the simultaneous radiation of multiple antenna beams. The structures include photonic manifolds that define equal-length optical paths and other optical paths whose lengths progressively change by a selected length .DELTA.L. The manifolds conduct signal pairs to radiative modules. Each signal pair includes a frequency-swept scanning signal s.sub.s and a reference signal s.sub.r whose frequency is a selected one of the sum and the difference of the frequencies of the scanning signal s.sub.s and a respective operating signal s.sub.o. Subsequently, the scanning signals are mixed with the reference signals and filtered to recover phase-shifted versions of each respective operating signal s.sub.o. The phase-shifted versions are radiated to form multiple radiated beams wherein each beam is scanned by changing the frequency of its respective scanning signal s.sub.s. The frequency of the scanning signals is selected to avoid generation of spurious radiated signals.

Abstract: Wideband phased array antennas are provided that eliminate the need for phase shifters in the region of the array face. In addition, they generate less beam squint than conventional antennas. In one embodiment, they include an electronic signal generator, reference and scanning manifolds and an array of n radiative modules. The signal generator generates a variable-frequency scanning signal s.sub.s and a reference signal s.sub.r wherein the frequency of the reference signal s.sub.r is substantially a selected one of the sum and the difference of the frequencies of the scanning signal s.sub.s and an operating signal s.sub.o. The reference manifold receives and divides the reference signal s.sub.r into n reference signal samples which are progressively time delayed by a selectable one of m reference differential time delays .DELTA.t.sub.r. The scanning manifold receives and divides the scanning signal s.sub.

Abstract: Mixing and modulating methods are described for nonlinear optical amplifiers (30) which can generate intermodulation products of radio-frequency signals in an optical carrier signal (26) without the penalty of an optical conversion loss and without the need for radio-frequency mixers, electro-optic modulators and expensive polarization-maintaining optical fibers. The radio-frequency signals can be applied to either a bias port (36) or an optical input port (32) of the optical amplifier and are used to upconvert and downconvert signals in phased-array antenna and remote antenna embodiments of the invention.

Abstract: An optical amplification system directs a diffraction-limited signal beam through a series of approximately 90.degree. crossings with a number of non-diffraction-limited pump beams in a photorefractive medium. All of the beams are s-polarized, resulting in an energy transfer from the pumps to the signal beam while leaving the signal beam diffraction-limited. The photorefractive medium is preferably a series of BaTiO.sub.3 :Rh crystals that receive the pump and signal beams through orthogonal faces, with their C-axes at approximately 45.degree. to both beams. A binary tree optical distribution network is used to minimize waveguide splits in forming a large number of pump beams.

Abstract: A spectral narrowing of the output bandwidth from a laser array is obtained by feeding back to the array a portion of its emitted light, while outputting the remainder of the light emitted from the array. An optical system to accomplish this preferably includes a pair of lenses, together with a diffraction grating that can be positioned either in-line with the laser array and lenses, or in a side-arm along with one of the lenses. The lenses can be set up so that light from each laser element is fed back either to itself, or to a symmetrically located element on the opposite side of the system axis. For a multi-lobe output from the laser array, one of the lobes is used for feedback and the others as outputs, resulting in a narrowing of the output angular divergence as well as of the output bandwidth.

Abstract: A rectangular light pipe (38) and associated optical elements (36), (40) are used to produce an overlapped combination of an array of aberrated laser beams (32), (34) inside a phase conjugate mirror (42). The beam array (32), (34) is focussed onto the entrance face (38a) of the light pipe (38) in such a way that each beam (32), (34) spreads by diffraction and internal reflections to fill the exit face (38b) of the light pipe (38). An image of the exit face (38b), which is completely filled by the overlapped beams (32), (34), is focussed into the phase conjugate mirror (42) such as to produce an overlap spot (46) size which is independent of beam aberation level. The apparatus preserves the linear polarization of the input beams (32), (34), has low optical loss, and may be incorporated into a 2 pass (50), (74) or 4 pass (80) phase conjugate master-oscillator power amplifier.

Abstract: A four-pass conjugate optical amplifier system and method are disclosed in which a linear polarized optical beam is directed by various optical elements through four passes of a power amplifier, preferably a diode laser structure. The beam is phase conjugated at the optical midpoint between the second and third amplifying passes, and is controlled by the optical elements so that its polarization is substantially the same during the first and second passes, and again substantially the same during the third and fourth amplifying passes. This is accomplished by a reflective coating on the back facet of the diode laser structure, with a non-reciprocal polarization rotation element located in the beam path between the phase conjugate mirror and power amplifier. For considerably enhanced power amplification, the beam may be divided into an array of subbeams, which are individually amplified by four passes through respective power amplifiers.

Abstract: A laser apparatus (10) has a coherent master oscillator radiation source (30) for driving a plurality of laser gain elements (20) positioned in a operationally parallel configuration so as to receive unamplified radiation (40) from master oscillator (30) and transmitting amplified radiation (44). Input means (60) couples portion of radiation (40) from master oscillator to each of said gain elements (20). Phase conjugate reflector means (80) operatively coupled to gain elements (20) reflects the phase conjugate of amplified radiation (44) back into the gain elements (20) where it is further amplified. Output coupling means (90) couples amplified radiation from the plurality of gain elements (20) out of the laser apparatus as a single coherent output beam of radiation.

Abstract: An imaging apparatus which permits the use of a transverse electrode electro-optic tunable filter (TEOTF), despite its obscured aperture, to produce a high quality image. The imaging apparatus includes a suitable conventional anamorphic input optical system in combination with a stacked plurality of TEOTFs in which the platelet of each TEOTF is made of an electro-optic material of a known index of refraction (such as CdS of an index of .about.2.4), and is clad between its surface and its electrodes with a material having a lower index of refraction than the platelet material (such as SiO.sub.2 of an index of .about.1.5).