Abstract: A variable optical attenuator device is described that comprises a first optical input, a first optical output, a first optical path between the first optical input and the first optical output, and means for moving a shutter across said first optical path. A hollow core waveguide is provided to substantially guide light along the first optical path of the device. The device may also be used to provide an analogue beam splitting or switch function in telecommunication systems and the like.

Abstract: An optical routing device is described that comprises a semiconductor substrate (52) having at least one optical input (4), a plurality of optical outputs (6,8) and an array of MEMS moveable reflective elements (58;102). The array of moveable reflective elements (58;102) are configurable such that light can be selectively routed from any one optical input (4) to any one of two or more of said plurality of optical outputs (6,8). Light selectively routed from any one optical input to any one of two or more of said plurality of optical outputs (6,8) is guided within a hollow core waveguide (54). In one embodiment, a cross-connect optical matrix switch is described.

Abstract: A transmitter apparatus (2) is described that comprises one or more lasers (4), modulation means (10) to intensity modulate radiation output by each of said one or more lasers (4), and output means for outputting the modulated radiation produced by the modulation means into, for example, an optical fiber (22). The apparatus comprises hollow core optical waveguides (20) formed in a substrate (18) which, in use, guide radiation from the one or more lasers (4) to the modulation means (10) and from the modulation means (10) to the output means. An associated receiver apparatus (30) is also described that comprises one or more detectors (32) and one or more optical fiber attachment means, the one or more optical fiber attachment means being arranged to receive one or more one optical fibers (42). The receiver is characterized in that radiation is guided from the one or more optical fibers (42) to the one or more detectors (32) by at least one hollow core optical waveguide (40) formed in a substrate.

Abstract: An optical routing device is described that comprises a semiconductor substrate (52) having at least one optical input (4), a plurality of optical outputs (6,8) and an array of MEMS moveable reflective elements (58;102). The array of moveable reflective elements (58;102) are configurable such that light can be selectively routed from any one optical input (4) to any one of two or more of said plurality of optical outputs (6,8). Light selectively routed from any one optical input to any one of two or more of said plurality of optical outputs (6,8) is guided within a hollow core waveguide (54). In one embodiment, a cross-connect optical matrix switch is described.

Abstract: An optical wavelength division multiplexer/demultiplexer device is described that comprises a substrate having a plurality of wavelength selecting filters. The filters are arranged to provide conversion between a combined beam comprising a plurality of wavelength channels and a plurality of separate beams each comprising a subset of said plurality of wavelength channels. Hollow core waveguides are formed in said substrate to guide light between the wavelength selecting filters. An add/drop multiplexer is also described.

Abstract: A photonic light circuit device is described that comprises a semiconductor substrate (220) and two or more optical components (226, 228, 236, 240) wherein one or more hollow core optical waveguides (230, 232, 224) are formed in the semiconductor substrate to optically link said two or more optical components. The PLC may comprise a lid portion (44) and a base portion (42). The PLC can be adapted to receive optical components (8:608) or optical components may be formed monolithically therein. Coating with a reflective layer is also described.

Abstract: A hollow core multi-mode interference (MMI) device is described that comprises a multi-mode waveguide (10, 14) optically coupled to at least two fundamental mode waveguides (8, 12, 16). The device is characterised in that it comprises a means for varying the internal cross-sectional dimensions of a portion of one or more of said at least two fundamental mode waveguides. In particular, the side wall of a fundamental mode waveguide having a substantially square cross-section can be moved using micro-electro mechanical systems (MEMS). Various optical routing devices incorporating such MMI devices are described.

Abstract: An optical amplifier is described that comprises at least two sections of amplifying optical fibre and pumping means for optically pumping the amplifying optical fibre. Optical fibre support means, for example a channel or channels in a substrate, are also provided to hold the two or more sections of amplifying optical fibre substantially straight during use. The optical fibre support means also includes a means for coupling light between the at least two sections of amplifying optical fibre. The at least one amplifying optical fibre may comprise an Erbium doped core to provide an erbium doped fibre amplifier (EDFA).

Abstract: Optical circuits for optical amplifier input and output stages are described. The input stage circuit (42) comprises a first optical waveguide (46) for carrying a signal beam to be amplified, a second optical waveguide (62) for carrying a pump beam, a beam combining means (58) optically coupled to the first and second optical waveguides (46, 62) for producing a combined signal/pump beam, and means for optically coupling the combined signal/pump beam into an amplifying optical fibre (63). The output stage circuit (44) comprises a first output optical waveguide (64), an optical fibre attachment means arranged to receive an amplifying optical fibre (63) and an optical fibre attachment means arranged to receive an output optical fibre (76) wherein light from the amplifying optical fibre (63) is optically coupled to the output optical fibre (76) via the first output optical waveguide (64).

Abstract: A waveguide laser (10) incorporates a guide (12) and two concave resonator mirrors (14, 16). The guide (12) is of square section with side (2a), and of length L equal to 4a.sup.2 /.lambda., where .lambda. is a laser operating wavelength. The mirrors (14, 16) are phase matched to respective Gaussian intensity profile radiation beams with beam waists at respective waveguide end apertures (20, 22). Each beam waist has a radius w.sub.0 in the range 0.1a to 0.65a to avoid waveguide edge effects and excitation of unwanted high order waveguide modes. The laser (10) has good transverse spatial mode characteristics.

Abstract: A laser device incorporates a rectangular multi-mode beamsplitter waveguide connected at one end to a retro-reflecting mirror. The beamsplitter waveguide is connected at a second end to an output coupling waveguide and a reflection coupling waveguide. The reflection coupling waveguide is terminated by a second retro-reflecting mirror. Radiation produced within the device is reflected by the mirror and coupled to the two coupling waveguides in a manner such that a partially reflecting mirror is not required at an output to the device.

Abstract: An optical mixing device (10) incorporates a rectangular multimode waveguide (14), with an input region (22) and an output region (24), two square section input waveguides (26, 28), and a detector (34). The input waveguides (26, 28) are arranged to provide first and second input radiation beams respectively to the input region (22), each beam being in the form of a square waveguide fundamental mode beam. Modal dispersion along the multimode waveguide (14) produces a single maximum incident on the detector (34) when the input beams are in phase with one another, and two maxima of like magnitude located on opposite sides of the detector (34) when the input beams are in antiphase. Intermediate these two situations three maxima are produced, the amplitudes depending on phase difference. The first and second input beams may be of like frequency producing a time-independent device output. The input beams may alternatively have different frequencies.

Abstract: A signal routing device (10) incorporates a multimode beamsplitter waveguide (20) connected by a set of parallel relay waveguides (22) to a multimode recombiner waveguide (24). Each relay waveguide (22) contains a respective electro-optic phase shifter (36). Sets of input and output waveguides (18, 28) are connected to the beamsplitter and recombiner waveguides (20, 24) respectively. The input and output waveguides (18, 28) are periodically spaced at off-center positions across the respective multimode waveguide transverse cross-section associated therewith. Radiation in any one of the input waveguides (18) is distributed between the relay waveguides (22) by virtue of modal dispersion in the beamsplitter waveguide (20). The phase shifters (36) apply a set of phase shifts to the distributed radiation. Modal dispersion in the recombiner waveguide (24) results in the phase shifted radiation providing a non-zero input to one or more of the output waveguides (28).

Abstract: An optical device (10) for use in beamsplitting, recombination and related applications incorporates a rectangular multimode waveguide (20) connecting a first coupling waveguide (18) to two second coupling waveguides (22, 24). The first coupling waveguide (18) operates in its fundamental mode and provides an input which excites a series of symmetric modes of the multimode waveguide (20). Modal dispersion along the multimode waveguide (20) provides for the input excitation (70a) to be transformed into separate output excitations (75a, 75b) cantered on respective second coupling waveguides (22, 24). The radiation intensity distribution (75) goes to zero at multimode waveguide end wall regions (54) between the second coupling waveguides (22, 24). This minimizes reflection and increased beamsplitting efficiency. The device (10) may be operated in reverse as a beam combiner.

Abstract: An optical device (10) incorporates a rectangular multimode waveguide (14) with an input aperture (22), and two output optical fibres (26 and 28) with respective input apertures (30 and 32). An input light beam (34) of Gaussian transverse intensity profile is focused to a beam waist (36) at the center of the aperture (22). The beam phase and waist radius w are arranged such that the light beam (34) excites symmetric modes in the waveguide (14). Modal dispersion along the waveguide (14) producestwo electric field intensittlVxima of similar magnitude centered on the fibre input apertures (30 and 32). This provides the beamsplitter function of division of input radiation into two similar intensity outputs. Devices of the invention may be arranged to divide input beams into more than two output beams. The invention may also provide a light beam combiner.

Abstract: An intensity dividing device (10) incorporates a rectangular multimode waveguide (20) connected to an input waveguide (18) and a set of four output waveguides (22). The input waveguide (18) provides a fundamental mode input excitation of CO.sub.2 laser radiation to the multimode waveguide (20). The input waveguide (18) is offset from the multimode waveguide longitudinal axis (24). Consequently, both symmetric and antisymmetric modes of the multimode waveguide (20) are excited. Modal dispersion along the multimode waveguide produces electric field intensity maxima of differing magnitude centred on respective output waveguides (22). This provides division of the input radiation into a range of differing intensity outputs.

Abstract: A ceramic evacuatable enclosure (10, 30, 42) such as a laser body is made by the following process. A first body portion (12, 41) is formed with a channel (18, 19, 20, 43, 45, 46) and second body portion (11, 31, 40) of the same ceramic material is provided. Mating surfaces are polished on the body portions (11, 12) for bonding together by thermocompression below the ceramic distortion temperature to achieve a vacuum seal. The ceramic may be alumina including 0.2 to 12% by weight of vitreous material. The thermocompression temperature may be in the range 1200.degree. C. to 1750.degree. C. Polishing is performed to a finish of from 0.01 .mu.m to 0.15 .mu.m. The body portions (11, 12) may have similar surface formations mutually aligned to provide a folded cavity (18, 19, 20) for an alumina waveguide CO.sub.2 laser.