An overview of the recent developments in the field of cylindrical vector beams is
provided. As one class of spatially variant polarization, cylindrical vector beams
are the axially symmetric beam solution to the full vector electromagnetic wave
equation. These beams can be generated via different active and passive methods.
Techniques for manipulating these beams while maintaining the polarization symmetry
have also been developed. Their special polarization symmetry gives rise to unique
high-numerical-aperture focusing properties that find important applications in
nanoscale optical imaging and manipulation. The prospects for cylindrical vector
beams and their applications in other fields are also briefly discussed.

Cylindrical vector beams: from mathematical concepts to applications

An introduction to heat transfer

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Soon after the discovery of lasers in the 1960s it was realized that laser therapy had the potential to improve wound healing and reduce pain, inflammation and swelling. In recent years the field sometimes known as photobiomodulation has broadened to include light-emitting diodes and other light sources, and the range of wavelengths used now includes many in the red and near infrared. The term “low level laser therapy” or LLLT has become widely recognized and implies the existence of the biphasic dose response or the Arndt-Schulz curve. This review will cover the mechanisms of action of LLLT at a cellular and at a tissular level and will summarize the various light sources and principles of dosimetry that are employed in clinical practice. The range of diseases, injuries, and conditions that can be benefited by LLLT will be summarized with an emphasis on those that have reported randomized controlled clinical trials. Serious life-threatening diseases such as stroke, heart attack, spinal cord injury, and traumatic brain injury may soon be amenable to LLLT therapy.

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The Nuts and Bolts of Low-level Laser (Light) Therapy

Light is often thought of in terms of radial polarization, but longitudinal polarization is also possible, and it has some intriguing possibilities for particle acceleration. Binary optics, combined with a high-numerical-aperture lens, is a potential route to achieving light with this unusual property.

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Creation of a needle of longitudinally polarized light in vacuum using binary optics

Light-emitting diodes (LEDs) come in many varieties and with a wide range of radiation patterns. We propose a general, simple but accurate analytic representation for the radiation pattern of the light emitted from an LED. To accurately render both the angular intensity distribution and the irradiance spatial pattern, a simple phenomenological model takes into account the emitting surfaces (chip, chip array, or phosphor surface), and the light redirected by both the reflecting cup and the encapsulating lens. Mathematically, the pattern is described as the sum of a maximum of two or three Gaussian or cosine-power functions. The resulting equation is widely applicable for any kind of LED of practical interest. We accurately model a wide variety of radiation patterns from several world-class manufacturers.

Modeling the radiation pattern of LEDs

Light extraction analysis of GaN-based light-emitting diodes (LEDs) with Monte Carlo ray tracing is presented To obtain high light extraction efficiency, periodic structures introduced on the top surface and/or on the substrate of various types of LED are simulated, including wire bonding, flip chip and Thin GaN Micro pyramid array with an apex angle from 20° to 70° is shown to effectively improve the light extraction efficiency In addition, for an LED encapsulated within an epoxy lens, the patterned substrate with pyramid array is found to be a more effective way to increase light extraction efficiency than the surface texture

Light extraction analysis of GaN-based light-emitting diodes with surface texture and/or patterned substrate

A novel LED modeling algorithm for precise three-dimensional light pattern simulation is proposed and demonstrated. We propose to use normalized cross correlation to verify the validity of the simulation in one-dimensional intensity patterns as well as two-dimensional irradiance patterns in various midfield distances and to provide feedback to achieve a successful model. The model is demonstrated to obtain an average of 99% in normalized cross correlation between the simulation light pattern and experimental measurement for a truncated inverse pyramid LED.

Precise optical modeling for LED lighting verified by cross correlation in the midfield region

An efficient LED lamp that illuminates the street with high quality is presented. The luminaire shows high optical efficiency, high optical utilization factor, low glare, and illuminates the street with high uniformity. The concept is simple but effective: a cluster of LEDs with TIR lenses are put inside a reflective box, which is covered with a microlens sheet; the reflective cavity improves efficiency by light recycling; each TIR lens collimates the LED light for the microlens array; and the microlens sheet uniformly distributes light only into the street. We verify its feasibility by Monte Carlo ray-tracing for the main types of road lighting arrangements: central, zigzag, and single-side pole positions.

High-performance LED street lighting using microlens arrays

A design for focusing an incoming light into an ultrasmall spot with a long depth of focus is proposed. We use a phase plate with three concentric regions to modulate the incoming light from radial polarization into outward-inward-outward polarization. The analysis shows that the design is more suitable for a lens with a high numerical aperture because much energy is concentrated in the main lobe of the focus spot.

Ching Cherng Sun

Papers

Modeling the radiation pattern of LEDs

Light extraction analysis of GaN-based light-emitting diodes with surface texture and/or patterned substrate

Precise optical modeling for LED lighting verified by cross correlation in the midfield region

High-performance LED street lighting using microlens arrays

Ultrasmall focusing spot with a long depth of focus based on polarization and phase modulation.