Browsing by Subject "Pigments"

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Open Access
Blue InGaN/GaN-based quantum electroabsorption modulators
(IEEE, 2006) Sarı, Emre; Nizamoğlu, Sedat.; Özel, Tuncay; Demir, Hilmi Volkan
We introduce InGaN/GaN-based quantum electroabsorption modulator that incorporates ∼5 nm thick In0.35Ga0.65N/GaN quantum structures for operation in the blue spectral range of 420-430 nm. This device exhibits an optical absorption coefficient change of ∼6000 cm-1 below the band edge at highly transmissive, blue region (at λ peak=424 nm) with a 6 V swing and emits blue light (at λpeak=440 nm) with an optical output power of 0.35 mW at a 20 mA current injection level. Unlike infrared III-V quantum modulators, this blue modulator shows a blue shift in its electroabsorption (for λ < 418 nm) with increasing applied field accross it, due to high alternating polarization fields in its quantum structures; this electroabsorption behavior is opposite to the conventional quantum confined Stark effect that features common red shift. This device holds great promise for > 10 GHz optical clock injection directly into silicon CMOS chips in the blue because of its low parasitic in-series resistance (< 100 Ω) and the possibility to make smaller device mesas for low capacitance (1.2 fF for a 10μm×10μm mesa size). Considering high-speed operation and high responsivity of silicon-on-insulator (SOI) photodetectors in the blue range, unlike in the infrared, this approach eliminates the need for on-chip hybrid integration of Si CMOS with III-V photodetectors. Furthermore, the efficient electroluminescence of this device makes it feasible to consider on-chip blue laser-modulator integration for a compact optical clocking scheme. © 2006 IEEE.
Open Access
White light generation with CdSe/ZnS core-shell nanocrystals and InGaN/GaN light emitting diodes
(IEEE, 2006) Nizamoğlu, Sedat; Özel, Sedat; Sarı, Emre; Demir, Hilmi Volkan
We present hybrid white light sources that integrate CdSe/ZnS core-shell nanocrystals on blue InGaN/GaN light emitting diodes (LED). We report on the demonstrations of white light generation using yellow nanocrystals (λPL=580 nm) hybridized on a blue LED (λEL= 440 nm) with tristimulus coordinates of x=0.37 and y=0.25, correlated color temperature of Tc=2692 K, and color rendering index of R a=14.6; cyan and red nanocrystals (λPL=500 nm and 620 nm) on a blue LED (λEL=440 nm) with x=0.37, y=0.28, T c=3246 K, and Ra=19.6; and green, yellow, and red nanocrystals (λPL=540 nm, 580 nm, and 620 nm) on a blue LED (λEL=452 nm) with x=0.30, y=0.28, Tc =7521 K, and Ra=40.9. © 2006 IEEE.