Properties that can now be achieved with advanced, blue indium gallium nitride light emitting diodes (LEDs) lead to their potential as replacements for existing infrastructure in general illumination, with important implications for efficient use of energy. Further advances in this technology will benefit from reexamination of the modes for incorporating this materials technology into lighting modules that manage light conversion, extraction, and distribution, in ways that minimize adverse thermal effects associated with operation, with packages that exploit the unique aspects of these light sources. We present here ideas in anisotropic etching, microscale device assembly/integration, and module configuration that address these challenges in unconventional ways. Various device demonstrations provide examples of the capabilities, including thin, flexible lighting "tapes" based on patterned phosphors and large collections of small light emitters on plastic substrates. Quantitative modeling and experimental evaluation of heat flow in such structures illustrates one particular, important aspect of their operation: small, distributed LEDs can be passively cooled simply by direct thermal transport through thin-film metallization used for electrical interconnect, providing an enhanced and scalable means to integrate these devices in modules for white light generation.gallium nitride | solid-state lighting | transfer printing I ndium gallium nitride-based (InGaN) blue light emitting diodes (LEDs) hold a dominant position in the rapidly growing solid-state lighting industry (1, 2). The materials and designs for the active components of these devices are increasingly well developed due to widespread research focus on these aspects over the last one and a half decades. Internal and external quantum efficiencies of greater than 70% (3) and 60% (3), respectively, with luminous efficacies larger than 200 lm∕W (4) and lifetimes of >50;000 h (5) are now possible. The efficacies (i.e., 249 lm∕W), exceed those of triphosphor fluorescent lamps (i.e., 90lm∕W), thereby making this technology an appealing choice for energy-efficient lighting systems (4). In particular, electricity consumption for lighting potentially could be cut in half using solid-state lighting (2). Although there remain opportunities for further improvements in these parameters, the emergence of LEDs into a ubiquitous technology for general illumination will rely critically on cost effective techniques for integrating the active materials into device packages, interconnecting them into modules, managing the accumulation of heat during their operation, and spatially homogenizing their light output at desired levels of chromaticity. Existing commercial methods use sophisticated, high-speed tools, but which are based on conceptually old procedures that exploit robotic systems to assemble material mechanically diced from a source wafer, with collections of bulk wires, lenses, and heat sinks in millimeter-scale packages, on a device-by-device basis, followed by separa...

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The relative coherence and phase are extracted from two-element, coherently coupled, vertical cavity surface emitting laser arrays. The array elements are defined optically by a photonic crystal pattern and electrically by ion implantation. We obtain the near and far fields experimentally under varying current injection. The Fraunhofer approximation is used to simulate propagation from the near to far field. The phase and coherence are extracted as fitting parameters to match the experimental and propagated far field patterns. The phase and coherence will aid in future array designs and in elucidating the phase-shifting mechanism.

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Abstract-Photonic crystals with single-and seven-point defects are used to achieve single-fundamental-mode operation of protonimplanted vertical-cavity surface-emitting lasers. The holes are etched at a variety of depths for various photonic crystal designs to investigate the influence on single-mode emission. Because protonimplantation provides weak transverse confinement in the form of thermal lensing, selective loss is not required to suppress lasing of extended photonic crystal modes. We show that etching the photonic crystals to shallow depths provides the ability to scale to large aperture sizes, while etching deeply allows single-mode emission of small diameter devices. Optimized designs exhibit a net reduction in loss relative to unetched control devices, as evidenced by a reduction in device threshold current.