Photonics and Optoelectronics

43-55

Authors: Abhay Kumar Singh

The intensive effort has made to design new amorphous chalcogenide alloy for the photovoltaic as well as other optoelectronics applications. This work describes a short over view on photovoltaic materials, the relevance of inorganic photovoltaic materials, the development history of Cu (InGa) Se (CIGS) photovoltaics, prospects of chalcogenide photovoltaics. Along with the successful synthesis of Cu20(In14Ga9)Se45Te12 (CIGST-1) and Cu25(In16Ga9)Se40Te10 (CIGST-2) chalcopyrite materials in amorphous form. Structural analysis of the bulk materials was performed from the X-ray diffraction (XRD), Field Emission Scanning Microscope (FSEM), Differential Thermal Analyzer (DTA) and micro Raman analysis. While, the presence of elemental concentrations has been confirmed from the Energy Dispersive Spectroscopy (EDS). Subsequently, thermally evaporated thin films surface morphology and roughness parameter have been analyzed by using the Atomic Force Microscopy (AFM). The 100nm thin films, current-voltage (I-V) and resistance-voltage (R-V) characteristics at room temperature and in the temperature range upto 200℃, under applied voltage range upto 40 V have also been discussed. Outcomes of the structural analysis demonstrates bulk materials have an overall amorphous structure, and their thermally evaporated deposited thin films have low roughness. Structural analysis also reveal bulk CIGST-2 composition has single phase amorphous structure. This material thin film has a smooth surface morphology with a lower and higher values of I and R at room temperature. While, in the temperature range up to 200℃ it has a higher and lower I and R respectively. The physical variation in these materials could be explained with the help of the chemical bond theory of solids.

65-69

Authors: Shilpa Jindal, Neena Gupta

The transmission of four active users has been illustrated with 5 WDM × 4 TDM × 4 CODE channel at 20 Gbps data rate 3 Dimensional Optical Code Division Multiple Access system based on newly designed Model A having signature sequences in temporal domain, spectral domain and spatial domain with optical orthogonal codes, cubic congruent operator from algebra theory respectively, using Galois field GF (5) with varying receiver attenuation on optsim simulation software. The results, numerically shown in terms of bit error rate and graphically represented in terms of eye diagram and signal strength, indicate that the novel 3D coding technique is designed to support four users with good BER with variable attenuation at the front end of the receiver.

74-77

Authors: M. Yin, R. Jones

As a factor to limit higher lasing temperature, the rapid lasing intensity degradation in mid-infrared InGaSb/ InAlGaSb quantum well (QW) laser diode has been found and analysed. Due to higher resistance, defects, produced and developed by driving current in p-cladding layer, destroy lattice structure and make the lasing intensity decay. SEM result confirms the defects appeared in p-cladding layer and induced by driving current. Non-radiative recombination induced by defects in the structure is confirmed to result in the optical emission decay at higher temperatures, through the analysis of the electroluminance.