The invention concerns a guided wave spatial filter (300) for receiving input radiation and outputting corresponding filtered output radiation, the filter comprising first and second waveguide sections (30, L3, L5) connected in series, the sections: (a) mutually matched for transmitting fundamental mode radiation components present in the input radiation therethrough to provide the output radiation; and (b) mutually mismatched for hindering higher-order mode radiation components present in the input radiation from propagating therethrough and contributing to the output radiation. The spatial filter (300) is implemented using rib waveguides (30) for the sections with associated relatively deeply and relatively shallowly etched structures (20, 310, 320) for imparting to the sections their radiation mode filtration characteristics. The spatial filter according to the invention can be incorporated into optical splitters and optical modulators to enhance their performance and desensitise them to higher-order mode radiation injected thereinto.

Guided wave spatial filter

A near single‐lobed far‐field pattern was obtained from coherent operation of a nonevanescently coupled AlGaAs laser diode array. A diffractive microlens array collimated the individual beams to approximate a plane wave, and diffractive coupling from an external cavity mirror provided mutual coherence. A diffraction‐limited far‐field pattern was observed with 82% of the power contained in the central lobe. The method is directly applicable to two‐dimensional laser arrays and can be implemented as a single thin optical element.

Coherent addition of AlGaAs lasers using microlenses and diffractive coupling

Power scalable, rectangular, multi-mode, self-imaging, waveguide technologies are used with various combination of large aperture configurations, 20, 50, 80, 322, 324, 326, 328, 330, 332, 334, 336, 338, Gaussian 360 and super-Gaussian 350 beam profiles, thermal management configurations 100, flared 240 and tapered 161 waveguide shapes, axial or zig-zag light propagation paths, diffractive wall couplers 304, 306, 308, 310, 312, 314, 316, 318, 320 and phase controller 200, flexibility 210, phased arrays 450, 490, beam combiners 530, 530', and separators 344, 430, and other features to generate, transport, and deliver high power laser beams.

Power scalable optical systems for generating, transporting, and delivering high power, high quality laser beams

The operation of a two-dimensional GaInAsP/InP diode laser array with CW power dissipation up to 500 W/cm/sup 2/ into a Si microchannel heat sink is discussed. The approximately 1*4-mm/sup 2/ laser array was used to characterize the heat sink, and the value of 0.040 degrees C cm/sup 2//W was obtained for the thermal resistance per unit area. The extrapolated value for a 1-cm/sup 2/ heated area is 0.070 degrees C cm/sup 2//W. >

Microchannel heat sinks for two-dimensional high-power-density diode laser arrays

Three classes of array modes of closely spaced antiguides are analyzed: coupled fundamental (element) modes, coupled first-order (element) modes, and modes adjacent to coupled fundamental modes. The behavior of coupled fundamental modes as a function of lateral index step is analyzed and explained from a ray-optics point of view. It is found that at resonance, for both coupled fundamental and first-order modes, the array-mode propagation constant is virtually identical to the propagation constant of the mode of a single, unperturbed antiguide. Several types of mode discrimination mechanisms are discussed. For devices with 3- mu m-wide antiguide cores and 1- mu m interelement spacing, intermodal discrimination values of 15-20 cm/sup -1/ can be achieved. Excellent agreement is found between experimental data and theoretical predictions based on the effective-index method. >

Phase-locked arrays of antiguides: model content and discrimination

Phase-locked arrays with monolithically integrated diffractive spatial filters are proposed and demonstrated. Noncollinear sets of antiguides separated by a half-Talbot distance favour in-phase-mode oscillation. Diffraction-limited fundamental-mode operation is obtained to over twice threshold and in far-field patterns with as much as 75% of the energy in the main lobe.

Phase-locked array of antiguided lasers with monolithic spatial filter

Surface‐emitting GaAlAs/GaAs linear laser arrays are fabricated using the ion milling technique. Low threshold current and differential quantum efficiency comparable to these of the cleaved device are obtained.

Surface‐emitting GaAlAs/GaAs linear laser arrays with etched mirrors

An ion milling method is disclosed that provides a manufacturing technique for mass producing microscopic surface features using a wide variety of media that includes semiconductors, metals, and glasses. In the preferred embodiment, vertical and 45 degree mirrors are formed simultaneously in semiconductor laser diodes in order to produce monolithic two dimensional arrays of surface emitting lasers. Standard double heterostructure semiconductor laser diodes are first grown on a wafer using metalorganic chemical vapor deposition techniques. An ion milling gun is oriented at a particular angle from the longitudinal axis of the active layer of the laser and emits a stream of atomic particles toward the lasers producing a generally two sided cut or notch that extends downward from the top surface of the semiconductor laser and traverses the active layer. The two sides of the cut consist of a vertical face that is perpendicular to the active layer and an inclined mirror surface that connects to the bottom of the vertical face and the slopes back upward to the top of the laser. Although the preferred utilization of this invention is the production of high power semiconductor laser arrays and subsequent wafer scale integration, the ion milling technique may be employed to construct a wide variety of micro-miniature radiation interfaces, reflectors, transmitters, or absorbers. Virtually any surface that requires a specifically determined configuration of uniform topography of atomic proportions may be produced.

Ion milling method

A semiconductor laser array with features providing good beam quality at high powers, first by employing a laterally unguided diffraction region in which light from a set of waveguides is re-imaged in accordance with the Talbot effect and two arrays of waveguides may be used to provide a spatial filtering effect to select a desired array mode. This provides a laser array with increased power per unit solid angle, and with additional advantages of ability to scale the device up to larger arrays, ability to control the electrical excitation of the device for better optimization, and improved modal discrimination. A second aspect of the invention is the use of a resonance condition in an antiguide array, to produce a uniform near-field intensity pattern and improved coupling and device coherence. This resonance structure may be combined with the Talbot-effect structure to suppress the out-of-phase mode, or the out-of-phase mode may be suppressed by other means, such as by introducing interelement radiation losses or absorption losses in the antiguide array.

Semiconductor laser array having high power and high beam quality

Conditions for stabilization of in‐phase or out‐of‐phase array eigenmodes in diffraction coupled diode laser arrays are derived and applied to several array architectures. The analysis predicts that the discrimination between these two eigenmodes is strongest in arrays with half Talbot distance long free‐propagation region. In this geometry, the out‐of‐phase and in‐phase near fields are, respectively, reproduced and channeled halfway between the original channel locations.

William W Simmons

Papers

Phase-locked array of antiguided lasers with monolithic spatial filter

Surface‐emitting GaAlAs/GaAs linear laser arrays with etched mirrors

Ion milling method

Semiconductor laser array having high power and high beam quality

Design considerations for diffraction coupled arrays with monolithically integrated self‐imaging cavities