Status and future outlook of III-V compound semiconductor visible-spectrum light-emitting diodes (LEDs) are presented. Light extraction techniques are reviewed and extraction efficiencies are quantified in the 60%+ (AlGaInP) and ~80% (InGaN) regimes for state-of-the-art devices. The phosphor-based white LED concept is reviewed and recent performance discussed, showing that high-power white LEDs now approach the 100-lm/W regime. Devices employing multiple phosphors for "warm" white color temperatures (~3000-4000 K) and high color rendering (CRI>80), which provide properties critical for many illumination applications, are discussed. Recent developments in chip design, packaging, and high current performance lead to very high luminance devices (~50 Mcd/m2 white at 1 A forward current in 1times1 mm2 chip) that are suitable for application to automotive forward lighting. A prognosis for future LED performance levels is considered given further improvements in internal quantum efficiency, which to date lag achievements in light extraction efficiency for InGaN LEDs

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Status and Future of High-Power Light-Emitting Diodes for Solid-State Lighting

This tutorial presents a guided tour of laser feedback interferometry, from its origin and early development through its implementation to a slew of sensing applications, including displacement, distance, velocity, flow, refractive index, and laser linewidth measurement Along the way, we provide a step-by-step derivation of the basic rate equations for a laser experiencing optical feedback starting from the standard Lang and Kobayashi model and detail their subsequent reduction in steady state to the excess-phase equation We construct a simple framework for interferometric sensing applications built around the laser under optical feedback and illustrate how this results in a series of straightforward models for many signals arising in laser feedback interferometry Finally, we indicate promising directions for future work that harnesses the self-mixing effect for sensing applications

Laser feedback interferometry: a tutorial on the self-mixing effect for coherent sensing

This book provides the reader with an understanding of what color is, where color comes from, and how color can be used correctly in many different applications. The authors first treat the physics of light and its interaction with matter at the atomic level, so that the origins of color can be appreciated. The intimate relationship between energy levels, orbital states, and electromagnetic waves helps to explain why diamonds shimmer, rubies are red, and the feathers of the Blue Jay are blue. Then, color theory is explained from its origin to the current state of the art, including image capture and display as well as the practical use of color in disciplines such as computer graphics, computer vision, photography, and film.

Color Imaging: Fundamentals and Applications

The recent developments in time-domain diffuse optics that rely on physical concepts (e.g., time-gating and null distance) and advanced photonic components (e.g., vertical cavity source-emitting laser as light sources, single photon avalanche diode, and silicon photomultipliers as detectors, fast-gating circuits, and time-to-digital converters for acquisition) are focused. This study shows how these tools could lead on one hand to compact and wearable time-domain devices for point-of-care diagnostics down to the consumer level and on the other hand to powerful systems with exceptional depth penetration and sensitivity.

https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics/volume-21/issue-9/091310/New-frontiers-in-time-domain-diffuse-optics-a-review/10.1117/1.JBO.21.9.091310.pdf

New frontiers in time-domain diffuse optics, a review

A gas inlet system for a wafer processing reactor includes a tubular gas manifold conduit adapted to be connected to a gas inlet port of the wafer processing reactor; and gas feeds including a first feed for feeding a first gas into the tubular gas manifold conduit and a second feed for feeding a second gas into the tubular gas manifold conduit. Each feed has two or more injection ports connected to the tubular gas manifold conduit at a first axial position of the tubular gas manifold conduit, and the injection ports of each of the gas feeds are evenly distributed along a circumference of the tubular gas manifold conduit at the first axial position.

Gas Supply Manifold And Method Of Supplying Gases To Chamber Using Same

The invention describes a heating system ( 100 ) and a corresponding method of heating a heating surface ( 180 ) of an object ( 150, 950 ) to a processing temperature of at least 100° C., wherein the heating system ( 100 ) comprises semiconductor light sources ( 115 ), and wherein the heating system ( 100 ) is adapted to heat an area element of the heating surface ( 180 ) with at least 50 semiconductor light sources ( 115 ) at the same time. The heating system ( 100 ) may be part of a reactor for processing semiconductor structures. The light emitted by means of the semiconductor light sources ( 115 ) overlaps at the heating surface ( 180 ). Differences of the characteristic of one single semiconductor light source ( 115 ) may be blurred at the heating surface ( 180 ) such that a homogeneous temperature distribution across a processing surface of a, for example, wafer may be enabled.

Heating system comprising semiconductor light sources

Projection systems have found widespread use in conference rooms and other professional applications during the last decade and are now entering the home TV market at a considerable pace. Projectors as small as about one litre are able to deliver several thousand screen lumens and are, with a system efficacy of over 10 lm W −1 , the most efficient display systems realized today. Short arc lamps are a key component for projection systems of the highest efficiency for small-size projection displays. The introduction of the ultra high performance (UHP) lamp system by Philips in 1995 can be identified as one of the key enablers of the commercial success of projection systems. The UHP lamp concept features outstanding arc luminance, a well suited spectrum, long life and excellent lumen maintenance. For the first time it combines a very high pressure mercury discharge lamp with extremely short and stable arc gap with a regenerative chemical cycle keeping the discharge walls free from blackening, leading to lifetimes of over 10 000 h. Since the introduction of the UHP lamp system, many important new technology improvements have been realized: burner designs for higher lamp power, advanced ignition systems, miniaturized electronic drivers and innovative reflector concepts. These achievements enabled the impressive increase of projector light output, a remarkable reduction in projector size and even higher optical efficiency in projection systems during the last years. In this paper the concept of the UHP lamp system is described, followed by a discussion of the technological evolution the UHP lamp has undergone so far. Last, but not least, the important improvements of the UHP lamp system including the electronic driver and the reflector are discussed. (Some figures in this article are in colour only in the electronic version)

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UHP lamp systems for projection applications

In this method an arc-length control value, indicating the current length of a discharge arc of the gas-discharge lamp (1), is monitored and the lamp (1) is driven in a first operation mode (OMP) with a first current wave-shape when the arc-length control value indicates that the arc-length is higher than a switching threshold, which first current wave-shape is selected to result in a tip (31) growing on an electrode (30) of the lamp (1), and the lamp (1) is driven in a second operation mode (OMn) with a second current wave-shape when the arc-length control value indicates that the arc-length is lower than a switching threshold, which second current wave-shape is selected such that the tip (31) on the electrode (30) is at least partly melted back. In this method an operating frequency of the lamp is switched from a first frequency value (fi) to a second frequency value (f2), which second frequency • (f 2) value is higher than the first frequency value (fi)', if a first time criterion pertaining to a duration of driving of the lamp (1) in the second operation mode (OMn) is fulfilled and the operating frequency is switched from the second frequency value (f2) to the first frequency value (fi), if a second time criterion pertaining to a duration of driving of the lamp (1) in the first operation mode (OMP) is fulfilled.

Method and driving unit for driving a gas-discharge lamp

Easy system design, compactness and a uniform power distribution define the basic advantages of high power VCSEL
systems. Full addressability in space and time add new dimensions for optimization and enable “digital photonic
production”. Many thermal processes benefit from the improved control i.e. heat is applied exactly where and when it is
needed. The compact VCSEL systems can be integrated into most manufacturing equipment, replacing batch processes
using large furnaces and reducing energy consumption. This paper will present how recent technological development of
high power VCSEL systems will extend efficiency and flexibility of thermal processes and replace not only laser
systems, lamps and furnaces but enable new ways of production.
High power VCSEL systems are made from many VCSEL chips, each comprising thousands of low power VCSELs.
Systems scalable in power from watts to multiple ten kilowatts and with various form factors utilize a common modular
building block concept. Designs for reliable high power VCSEL arrays and systems can be developed and tested on each
building block level and benefit from the low power density and excellent reliability of the VCSELs. Furthermore
advanced assembly concepts aim to reduce the number of individual processes and components and make the whole
system even more simple and reliable.

High-power VCSEL systems and applications

A method and a circuit arrangement for operating a discharge lamp, in particular during the first hours of operation after lamp manufacture, are described. The method and the circuit arrangement are provided in particular for high-pressure gas discharge lamps (HID or high intensity discharge lamps or UHP or ultra high performance lamps). Furthermore, a lighting unit with a discharge lamp and such a circuit arrangement and a projection system with a projection display and such a lighting unit are described. Switching-over between various modes of operation with different operating frequencies serves to avoid that the burning voltage of the lamp drops into a region of a minimum voltage of a lamp driver unit below which the latter can no longer drive the lamp with its rated power or a desired power.

Pavel Pekarski

Papers

Heating system comprising semiconductor light sources

UHP lamp systems for projection applications

Method and driving unit for driving a gas-discharge lamp

High-power VCSEL systems and applications

Method and circuit arrangement for operating a discharge lamp