In this work, design of a photonic crystal (PhC) based structure is proposed for efficient splitting of light from broadband Light Emitting Diode (LED) into multiple narrowband sources. InP based transverse junction LED is considered. A vertical stack of two-dimensional (2D) square lattice PhC made up of GaAs/air is placed on top of this LED. 2D periodicity of the PhC is in the vertical plane of the top surface of the LED. On removal of a few GaAs rods the broadband light is focussed by effect of superlensing on the resulting T-type channel. The simulated result is studied by creation of curved air hole on the superlensing PhC. Only TM polarized light of specific wavelength ranges from the LED source is considered for narrowbands splitting as the TE polarized light does not have suitable bandgap there. © 2017, Springer Science+Business Media New York.

RAJIB CHAKRABORTY

Applied Optics and Photonics

R GHOSH

K K GHOSH

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Optical and Quantum Electronics

Analysis has been done of improvement of forward directional light extraction efficiency of light emitting diodes (LEDs) by surface patterning of different types of one-dimensional profiles on indium-zinc-oxide films developed recently by our group using sol-gel technique. Finite-difference time-domain simulations by MEEP software have been used for this purpose. From the analysis, it is found that the patterned film is suitable for near-infrared LED. The optimized structure, which gives maximum improvement at around 1.040 μm wavelength, is determined and fabricated using soft lithography. Further enhancement of the light output of the LED with the fabricated gratings is possible by introducing an interlayer within the top contact layer. The mathematical formulation of the coupling of light in structured/multilayered surfaces is also discussed. © 2015 Optical Society of America.

Applied Optics

Further enhancement of light extraction efficiency from light emitting diode using triangular surface grating and thin interface layer

A 1D binary periodicstructure with defect has been analysed using Transfer Matrix Method. For a particular nine layered structure of SiO2 and InP, a number of full stop bands (in other words, zero passbands or forbidden bands) at different regions of the spectrum under investigation are observed. Introducing a central spatial defect in the system by adjusting the layer width, it is possible to achieve an extremely narrow passband centred on 1554.9 nm in the 7th forbidden band. Moreover by varying the defect width, the number of passbands can be increased. These passbands have flat and 100% stopband and hence can be better candidate to drop single or multiple frequencies in WDM systems. It is further observed that with increase in the number of layers and/or defect width, the number of mini pass bands outside the original forbidden band also increases. Also by FDTD simulation it is seen that the field is localised within the defect for the passband frequency. © 2012 Elsevier B.V. All rights reserved.

Journal	Data powered by TypesetOptical and Quantum Electronics
Publisher	Data powered by TypesetSpringer New York LLC
ISSN	0306-8919