A transfer-matrix method is used to study the distribution and polarization of circular waves in a waveguide with circular gratings. The method enables us to design gratings for a TE or TM wave. If the waveguide is a weak one, the in-plane components of the electrical field of a TM wave are small and the wave can be regarded as linearly polarized. If the waveguide does not have TE-TM wave birefringence, we find that a mixture of a TM1 wave with a small portion of TE1 wave is a linearly polarized LP0 wave in the waveguide plane. However, unlike the LP0 wave in a fiber, the in-plane component of the electrical field is not circularly symmetric.

Results will be presented on the variation of threshold current and emission wavelength with temperature of MQW InGaAs/GaAs circular-grating, surface-emitting, distributed Bragg reflector (CG-SE-DBR) lasers, in the range 10 - 90 degree(s)C. The structures were grown by one-step MBE and the circular gratings were defined by electron-beam lithography. Measurements were made pulsed and CW. The characteristic temperature ranged between 18 - 48 K. A wavelength variation with temperature of around 0.1 nm/ degree(s)C was obtained. The results are compared with those of linear, GaAs-based DBR lasers.

An optical interconnection system is being developed to provide vertical, digital data channels for stacked multichip modules. A key component of the system is an array of individually addressable vertical-cavity surface-emitting lasers with diffractive lenses integrated into the substrate to control beam divergence and direction. The lenses were fabricated by direct-write e-beam lithography and reactive ion beam etching into the GaAs substrate. Preliminary device performance data and the design and fabrication issues are discussed.

The surface emission efficiency of grating coupled surface emitters, defined as the fraction of the guided mode power incident on the grating outcoupler that is emitted into air, is limited by diffraction into the substrate. This paper presents results from experimental and theoretical studies of various techniques to suppress substrate emission from second order gratings while simultaneously enhance the emission into air. These techniques include optimized rectangular gratings, blazed asymmetric gratings, and laser structures incorporating multilayer reflectors below the waveguide to redirect light diffracted into the substrate. Optimized rectangular gratings exhibit more than 60% surface emission efficiency under appropriate detuning conditions. Blazed asymmetric gratings demonstrate a strong dependence of the surface emission efficiency on the orientation of the grating with respect to the propagation direction of the guided optical mode under both resonant and nonresonant conditions. Lasers with multilayer reflectors show promising performance with a precisely adjusted phase of the reflected wave. Techniques for fine tuning the phase difference between the reflected wave and the wave diffracted into air are discussed. The fabrication techniques used to fabricate the high quality gratings required for high performance surface emitters are also reviewed.

In optical signal processing, the implementation of quantum holography has advance considerably since the last few years. Specifically micro-optical devices such as 2D planar arrays of diffractive microlenses have recently received considerably attention in the optics R & D community. In this paper it is established that the symmetries as expressed by the non- split central group extensions... of quantum holography represent the unified mathematical approach to confocal scanning microscopy by planar point arrays, micro-optics layers of diffractive circular-grating laser structures, resonant components, nuclear magnetic resonance imaging including echo-planar imaging and functional magnetic resonance imaging and nuclear magnetic resonance microscopy.

Vertical-cavity surface-emitting lasers (VCSELs) have unique properties that distinguish them from conventional edge-emitting semiconductor lasers and render them very attractive for a number of novel applications. In addition to those distinguishing features, due to intense heating the role of thermal effects in VCSELs is by far more prominent than in edge emitters. In this paper, a brief review is given of some of VCSEL properties influenced by temperature. Effects of temperature on spectral device characteristics are discussed, including the temperature dependence of the longitudinal mode spectra and the transverse-mode structure. A new condition is formulated for thermal matching of the Bragg mirrors and the spacer region. Temperature sensitivity of threshold current is also considered, and the dominant role of the gain peak/cavity resonance detuning is described.

This paper reviews the state-of-the-art performance of producible, 850-nm, current-guided GaAs/AlGaAs, top-emitting vertical-cavity surface-emitting lasers (VCSELs) and arrays. We focus on the flexibility of this technology platform in demonstrating a variety of devices and arrays. This includes a 99.8% device yield across a 3-in-dia. Metal-Organic Vapor Phase Epitaxy (MOVPE)-grown wafer and wavelength operation across approximately equals 100-nm range. Recent progress in device performance (V_th equals 1.55 V; I_th equals 0.68 mA; P_cw equals 59 mW; T_cw equals 200 degree(s)C, (eta) _wp equals 28%) have and will enable great advances in VCSEL-array-based technologies. Included are unique ways of engineering modal characteristics from single-mode to quasi-incoherent emission. Array applications include 1D addressable arrays, particularly in the area of high-speed optical data links. An example application is the 32-channel-wide Optoelectronic Technology Consortium parallel links that have been operated error-free up to 980 Mbit/s (Manchester coded) through 100 m of bier. Two-dimensional matrix-addressable VCSEL arrays for processing and imaging applications will also be reviewed. Finally, we will discuss the exploitation of this VCSEL technology to explore the use of patterned or phased arrays of VCSELs. Their performance and relevant physics will be described, including the recent demonstration of in-phase coupling, watt-level emission, and multi-transverse-element mode coupling.

Broad stripe semiconductor lasers and laser arrays are capable of generating high optical output powers, but the transverse mode structure is generally poor. Two ways of improving the transverse mode structure by integrating spatial mode filters within the semiconductor lasers are discussed. Firstly, the far-field pattern of 980 nm broad area lasers has been improved by placing passive, low-loss slab waveguides on either side of the active region. Control devices exhibited a broad far-field spectrum (10 degree(s)) containing several peaks. Lasers with passive slab waveguides on both sides of the active region exhibited a single peak in the far-field spectrum, the divergence of which decreased as the length of the passive sections was increased. Secondly, novel antiguided arrays lasers have been fabricated by processes which are free of epitaxial regrowth stages. The operation of antiguided array lasers is dependent on the creation of an effective refractive index step between the antiguide core and the interelement regions. We describe the fabrication of five-element antiguided laser arrays at 1.48 micrometers in which undoped passive waveguiding layers have been added to the standard laser design. These waveguides significantly alter the shape of the far field emission from the lasers, showing that the array elements are pulled in-phase with each other. We also describe a second technique, using zinc diffusion to disorder a superlattice cladding layer, for creating the necessary index step in a ten-element antiguided laser array operating at 0.860 micrometers . Output powers approach 400 mW per facet into a 3^(DOT) (FWHM) beam.

The phenomenon of indium migration off the sidewalls of features on patterned GaAs substrates during MBE growth has been studied. The level of migration depends strongly on the arsenic flux and the growth temperature. Modulating the arsenic flux during the growth of multilayer structures allows the number of active quantum wells to vary from one region of a device to another.

An overview and comparison of both the low pressure metal-organic chemical vapor deposition (MOCVD) and the atomic layer epitaxy of InAs/InP strained heterostructures is presented. Control of the As/P interface down to the one monolayer regime allows the realization of quantum dots (QD) on terraced InP substrates by conventional MOCVD. These embedded InAs QD within the binary matrix show strong blue-shifted luminescence, which is indicative of multi-dimensionally confined structures with no significant interface defects. As a preliminary step towards the incorporation of these QDs in optoelectronic device structures, we also summarize the test results of broad area laser diodes fabricated on structures incorporating strained ultra-thin InAs quantum wells in the active region.

We report on the spectral properties of an inhomogeneously-pumped circular-grating distributed-feedback semiconductor laser. Numerically modeling the exact coupled-mode equations, we find that, in comparison with the homogeneous case, a Gaussian optical pump results in greater azimuthal mode discrimination, a broader multi-mode spectral envelope, and a wider fundamental linewidth.

In this paper, we report on the design and fabrication of electrically-pumped circular-grating surface-emitting DBR lasers for operation in 0.98 micrometers wavelength range. The layer structure consists of InGaAs/GaAs/AlGaAs strained multi-quantum-wells grown by one step epitaxial growth. Circular gratings are defined by electron-beam lithography around the circular gain sections. The effect of various parameters are discussed and the most recent results are presented.

We present a circular grating that encodes phase variations in the form of a daisy flower, or a pie, with several slices, or petals, with equal central angle and every other slice having a delay of (lambda) /2. We suggest the use of this type of grating for optical alignment.