Article

# Enhanced Light Extraction by Photonic Quasi-Crystals in GaN Blue LEDs

Univ. of Bath, Bath, UK
(Impact Factor: 2.83). 09/2009; 15(4):1269 - 1274. DOI: 10.1109/JSTQE.2009.2016674
Source: IEEE Xplore

ABSTRACT

The far-field profile of photonic quasi-crystal patterned and unpatterned LEDs, fabricated from commercial epitaxial substrates by electron beam lithography, has been measured prior to lapping and dicing. Emission enhancements reach a maximum of 62%, and are strongly dependent on the filling factor. Qualitative agreement is achieved between 2-D finite-difference time-domain calculations and the experimental data.

### Full-text

Available from: Wang Nang Wang,
0 Followers
·
• Source
• "Photonic quasi-crystal cladding results in unusual characteristics which are not noticeable in photonic crystal cladding. Over the years, photonic quasi-crystals have been playing an indispensable role for enhancing the light extraction in III-Nitrides based light-emitting diodes (LEDs) [17], [18] and Organic LEDs [19]. In addition, they also help increase the light trapping capability in thin film silicon solar cell [20]. "
##### Article: Large Pitch Photonic Quasi-Crystal Fiber Amplifier
[Hide abstract]
ABSTRACT: We design an ytterbium-doped large pitch photonic quasi-crystal fiber (PQF) for amplifying high-energy ultrashort laser pulses. The proposed fiber exhibits unique properties such as very large mode area (4660 $\mu\hbox{m}^{2}$), less attenuation (0.42 dB/km), high overlapping factor (0.55 for the fundamental mode), and low bending loss. These properties help amplify with high-average power ultrashort pulses with less distortion and high efficiency. To meet these requirements, we design a fiber with optimum gain filtering as well as loss filtering. From the numerical simulation of the analytical model, we confirm that the large pitch PQF plays an indispensable role in amplifying high-energy ultrashort pulses.
IEEE Photonics Journal 06/2012; 4(3):943-951. DOI:10.1109/JPHOT.2012.2201147 · 2.21 Impact Factor
• ##### Article: Photonic Quasi-Crystal Light Emitting Diodes, - comparisons of device performance with pattern pitch
[Hide abstract]
ABSTRACT: In this paper we discuss theoretical modelling methods for the design of photonic crystal and photonic quasi-crystal (PQC) LEDs - and apply them to the analysis of the extraction enhancement performance and shaping of the emitted beam profile of PQC-LED structures. In particular we investigate the effect of the pitch of the PQC patterning, and consider the physical mechanisms giving rise to performance improvements. In addition, we examine the relative contributions to performance improvements from effective index reduction effects that alter the conditions for total internal reflection at the device air interface, and from photonic crystal scattering effects that give rise to radically improved extraction performance. Comparisons are made with the performance of recently fabricated devices.
Proceedings of SPIE - The International Society for Optical Engineering 04/2010; 7713. DOI:10.1117/12.853796 · 0.20 Impact Factor
• ##### Article: High-efficiency Photonic Quasi-crystal Light Emitting Diodes Incorporating Buried Photonic Crystal Structures.
[Hide abstract]
ABSTRACT: In this paper we investigate the utilization of a patterned photonic crystal layer positioned below the Multiple Quantum Well region of a p-side up LED to improve light extraction and investigate the benefit of adding additional top surface photonic crystal patterning to the same device. Performance for each design is evaluated in terms of angular extraction efficiency and far field angular beam profile for fixed lattice geometry and a range of etch depths. We show that a buried photonic crystal lattice improves extraction for emission angles below the critical angle for total internal reflection, and does not have a detrimental effect over the normal extraction cone of the LED. An improvement of (33% to 57% in extraction efficiency is obtained using a buried photonic crystal lattice alone. The introduction of additional top surface patterning has potential to further improve the extraction efficiency up to 73%, and to tailor the shape of the emission profile.
Proceedings of SPIE - The International Society for Optical Engineering 08/2010; 7784. DOI:10.1117/12.860585 · 0.20 Impact Factor