A monolithic multi-wavelength LED based on selective dielectric cap intermixing is investigated experimentally. The proposed LED is fabricated on a QW structure and it has an independent wavelength intensity power control for each wavelength. The device consists of three regions that have been intermixed to varying extents of SiO2 thicknesses then annealed at 975°C for 20s.The regions are blue shifted by amounts that depend on the thickness of a SiO2 capping film. Contact stripes are then evaporated on each region as intensity power control to emit its respective wavelength. Experimental results showed an independently tri-wavelength emission of 797nm, 780nm and 775nm.
KEYWORDS: Optical fibers, Absorption, Single mode fibers, Gamma radiation, Oxygen, Cladding, Signal attenuation, Chemical species, Standards development, Surgery
This article presents the effect of low-dose gamma-ray irradiation on a newly developed randomly distributed holes
optical fiber (RDHF). The single-mode fiber has a cladding diameter of 125 μm and 0.21 dB/km attenuation in the 1550
nm wavelength. The effect of gamma irradiation on the presented fibers was studied by comparing their transmission
performance at 1550 nm wavelength with standard single-mode telecommunication fiber (SMF). RDHF along with SMF
were irradiated with 0.662 MeV gamma-rays at absorbed dose rate of 4 mGy(Si)/hr and total dose of 1.5 Gy(Si). Results
revealed that the performance of optical fiber under irradiation is not only dependent on the bulk material but also on the
physical structure of the fiber.
Monitoring of chemical species is important to a number of industrial and energy related industries. This paper presents a comparison of two fiber optic sensing schemes which are demonstrated for the detection of acetylene and carbon monoxide. The first sensor configuration utilizes the newly developed random hole optical fiber and detects gases entering into the holes in the fiber through the interaction with the evanescent field. The second scheme utilizes a hollow micro-capillary tube based fiber optic sensor system. In both systems, the detection of the chemical species is accomplished by analysis of the infrared absorption spectra produced by the species present in the path of the optical signal. The effect of varying pressure, micro-capillary tube diameter, capillary tube length, and gas species is presented.
It is suggested by this investigation, that light emission from Porous Silicon is due to the recombination of excitons generated in different locations. The majority of excitons generate from the nano-size crystalline silicone. However, excitons generated from amorphous silicon/SiO2 interface are also contributing to the whole excitons population in the material. Further, it is suggested that all excitons are confined and recombine in amorphous region.
Several models were presented in literature to explain the photoluminescence of porous silicon, suggesting carriers originate in Si nano-structure and recombine on the surface. None of the models have a clear justification on such carriers generation and carriers dynamics with respect to the mass conservation law, since the carriers are known to originate in one place and recombine in other. In this investigation a qualitative model, namely, the Virtual Band Model (VBM) is proposed to fill in the gabs which are raised in literature.
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