The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Thank you for reading principles of optics electromagnetic theory of propagation interference and diffraction of light. As you may know, people have search hundreds times for their favorite novels like this principles of optics electromagnetic theory of propagation interference and diffraction of light, but end up in harmful downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they are facing with some infectious bugs inside their computer.

Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

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.

/pdf/light-emitting-diodes-ubzde6g9qc.pdf

Light-emitting diodes

Over the past decade, advances in LEDs have enabled the potential for wide-scale replacement of traditional lighting with solid-state light sources. If LED performance targets are realized, solid-state lighting will provide significant energy savings, important environmental benefits, and dramatically new ways to utilize and control light. In this paper, we review LED performance targets that are needed to achieve these benefits and highlight some of the remaining technical challenges. We describe recent advances in LED materials and novel device concepts that show promise for realizing the full potential of LED-based white lighting.

LEDs for Solid-State Lighting: Performance Challenges and Recent Advances

Blue light-emitting diodes with a light extraction efficiency of 73% are reported. The InGaN–GaN devices use a photonic-crystal structure for superior optical mode control; their performance has been characterized experimentally and modelled theoretically.

III -nitride photonic-crystal light-emitting diodes with high extraction efficiency

We report on continuous wave lasing characteristics of GaN vertical cavity surface emitting lasers (VCSELs). The VCSEL operates at room temperature under current injection by using highly reflective distributed Bragg reflectors (DBRs) made up of transparent ${\rm ZrO}_{2}$ and ${\rm SiO}_{2}$ film stacks. Together with high reflectivity and the wide stop band of the DBR, the long cavity of 6 $\mu{\rm m}$ allows multimode lasing oscillation with narrow mode spacing of 2.9 nm. In addition, a short cavity structure of 2 $\mu{\rm m}$ is fabricated and shows quasi-single mode operation. The spacing of the lasing modes shows a clear dependence of the actual cavity lengths with fairly good agreement to theory taking account of the refractive index dispersion.

Continuous Wave Operation of GaN Vertical Cavity Surface Emitting Lasers at Room Temperature

An n-type buffer layer composed of n-type GaN, an n-type cladding layer composed of n-type AlGaN, an n-type optical confinement layer composed of n-type GaN, a single quantum well active layer composed of undoped GaInN, a p-type optical confinement layer composed of p-type GaN, a p-type cladding layer composed of p-type AlGaN, and a p-type contact layer composed of p-type GaN are formed on a substrate composed of sapphire. A current blocking layer formed in an upper portion of the p-type cladding layer and on both sides of the p-type contact layer to define a ridge portion is composed of a dielectric material obtained by replacing some of nitrogen atoms composing a Group III-V nitride semiconductor with oxygen atoms.

Semiconductor light-emitting device and method for fabricating the same

We have integrated the surface photonic crystal (PhC) on GaN-based blue light-emitting diodes (LEDs) for the first time in order to enhance the extraction efficiency of the LEDs. With the finite-difference time-domain method, we have calculated 3.6-fold enhancement in light output. The theoretical calculations have revealed that the optimum pitch of the PhC is much longer than the emission wavelength when the distance between the PhC and the active layer of LEDs is short. This design enables PhC formation on chemically stable GaN surfaces. In addition, an indium tin oxide (ITO)-based transparent electrode is formed directly on the surface of PhC to realize light emission from the whole area of the LED. The fabricated PhCs have increased the light output of blue LEDs by 1.5 times compared with the LEDs without PhC. We have demonstrated that PhC will realize highly efficient solid-state lighting with GaN-based LEDs.

https://iopscience.iop.org/article/10.1143/JJAP.43.5809/pdf

High-extraction-efficiency blue light-emitting diode using extended-pitch photonic crystal

This report reveals that diffusion of hydrogen induces gradual degradation in InGaN-based laser diodes (LDs). The increase in nonradiative recombination centers (NRCs) in the LDs has been attributed to diffusion-related phenomena. Factors other than NRCs, such as the threshold carrier density Nth, can increase threshold current Ith. Those factors, however, were not fully investigated. Moreover, the diffusant responsible for the degradation of the LDs has not been univocally identified yet. To separately evaluate the roles of NRCs and Nth in increasing Ith, this report analyzes the stress-induced variation of nonradiative recombination lifetime τnr and lasing wavelength λl. It is revealed that the density of NRCs increases at the first stage of gradual degradation, followed by a rise in Nth. In addition, this report proposes a novel model for the time-variation of 1/τnr to investigate the diffusion-related degradation. By using this model, we extrapolate the value of the diffusion coefficient of diffusants involved in the degradation in InGaN-based LDs. The proposed analysis methods and obtained results are useful for understanding the physics of LD degradation.

Analysis of Diffusion-Related Gradual Degradation of InGaN-Based Laser Diodes

This paper reports an extensive analysis of the properties of the deep level responsible for the degradation of InGaN-based laser diodes. The analysis is based on combined optical measurements and Deep-Level Transient Spectroscopy (DLTS) investigation. Results indicate that stress induces a significant increase in threshold current of the devices, which is strongly correlated to the increase in the concentration of a deep level (DL) detected by DLTS. The DL involved in the degradation process is located 0.35–0.45 eV below the conduction band. 2D simulation indicates that degradation occurs within the quantum-well region.

Shinichi Takigawa

Papers

Continuous Wave Operation of GaN Vertical Cavity Surface Emitting Lasers at Room Temperature

Semiconductor light-emitting device and method for fabricating the same

High-extraction-efficiency blue light-emitting diode using extended-pitch photonic crystal

Analysis of Diffusion-Related Gradual Degradation of InGaN-Based Laser Diodes

Investigation of the deep level involved in InGaN laser degradation by deep level transient spectroscopy