Physical properties of GalnAsSb-based type-I quantum well 2.3μm and 2.6μm edge emit... more Physical properties of GalnAsSb-based type-I quantum well 2.3μm and 2.6μm edge emitting lasers are investigated using spontaneous emission and hydrostatic pressure techniques. Temperature dependence spontaneous emission analysis on GalnAsSb/AlGaAsSb (1.6%) compressively strained EEL emitting at 2.3pm shows that at least 81+-5% of the threshold current at room temperature is due to non-radiative recombination. It is also shown that Auger recombination (CHLH and/ or CHSH) is the dominating non-radiative process. It is also shown that non-pinning of the carrier density above threshold causes the external differential efficiency of these 2.3 μm to decrease. There is also evidence of defect related recombination. For the 2.6μm devices made of GalnAsSb/GaSb 1.7% compressively strained quantum well, at least 97+-2% of threshold at room temperature is due to non radiative recombination. It is also shown that Auger current is the dominant process. There is also evidence of hole leakage and defect current in the 2.6μm EELs. T0 analysis show evidence of optical loss process suspected to be IVBA occurring which may couple the effects of non-pinning of the carrier density above threshold to cause the decreasing external differential efficiency observed in the devices. Investigation of GalnAsSb/AlGaAsSb 2.3μm VCSELs shows that the gain peak and cavity mode are aligned at T~260+-10K. The analyses here suggest that for improved performance of the 2.3pm VCSEL, the gain peak should be shifted to higher energies by approximately 10meV. For the GalnAsSb/GaSb 2.6μm VCSEL, the gain peak- cavity mode alignment is estimated to be at higher temperature (T=330+-10K) while the temperature insensitive region is obtained at T~200+-20K. It is estimated that by shifting the gain peak to higher energies (by approximately 8meV), the temperature insensitive region can be shifted to room temperature. Spontaneous emission analysis on 5 stage “W” interband cascade lasers (ICLs)show that at least 93+-2% of threshold current is due to non-radiative recombination. Pressure dependence of threshold current at 100K, 200K and 293K suggest that Auger recombination is the dominant loss process and is significant even at low temperatures. Considering the complex valence band structure of the “W” ICLs, it is possible that the CHLH Auger process is occurring even though the CHSH and CHCC are theoretically shown to be supressed. It is also shown that non-pinning of the carrier density above threshold causes the differential efficiency of the “W” ICL to decrease but IVBA may also be partly responsible
Journal of Data Analysis and Information Processing, 2021
The ability of machine learning techniques to make accurate predications is increasing. The aim o... more The ability of machine learning techniques to make accurate predications is increasing. The aim of this work is to apply machine learning techniques such as Support Vector Machine, Naïve Bayes, Decision Tree, Logistic Regression, and K-Nearest Neighbour algorithms to predict the shelf life of Okra. Predicting the shelf life of Okra is important because Okra becomes harmful for human consumption if consumed after its shelf life. Okra parameters such as weight loss, firmness, Titrable Acid, Total Soluble Solids, Vitamin C/Ascorbic acid content, and PH were used as inputs into these machine learning techniques. Support Vector Machine, Naïve Bayes and Decision Tree each accurately predicted the shelf life of Okra with accuracies of 100%. However, the Logistic Regression and K-Nearest Neighbour achieved 88.89% and 88.33% accuracies, respectively. These results showed that machine learning techniques especially Support Vector Machine, Naïve Bayes and Decision Tree can be effectively applied for the prediction of Okra shelf life.
IEEE Journal of Selected Topics in Quantum Electronics, 2017
The efficiency limiting mechanisms in type-I GaInAsSb-based quantum well (QW) lasers, emitting at... more The efficiency limiting mechanisms in type-I GaInAsSb-based quantum well (QW) lasers, emitting at 2.3, 2.6 and 2.9 µm, are investigated. Temperature characterization techniques and measurements under hydrostatic pressure identify an Auger process as the dominant nonradiative recombination mechanism in these devices. The results are supplemented with hydrostatic pressure measurements from three additional type-I GaInAsSb lasers, extending the wavelength range under investigation from 1.85 to 2.90 µm. Under hydrostatic pressure, contributions from the CHCC and CHSH Auger mechanisms to the threshold current density can be investigated separately. A simple model is used to fit the nonradiative component of the threshold current density, identifying the dominance of the different Auger losses across the wavelength range of operation. The CHCC mechanism is shown to be the dominant nonradiative process at longer wavelengths (> 2 µm). At shorter wavelengths (< 2 µm), the CHSH mechanism begins to dominate the threshold current, as the bandgap approaches resonance with the spin-orbit split-off band.
The success obtained from semiconductor laser devices is dependent on the science of manipulating... more The success obtained from semiconductor laser devices is dependent on the science of manipulating the electron-hole and the photon. While the most useful interaction in the laser is the recombination process that involves the electron and holes to produce a photon, other non-useful processes also occur and in some cases overshadow the preferred recombination process. In this review article, the physics behind radiative and non-radiative recombination processes and loss mechanisms dominant in quantum well semiconductor lasers is presented. The work concludes by suggesting possible solutions based on relevant published works
We present a Scanning Electron Microscopy (SEM) technique for the characterisation of biological ... more We present a Scanning Electron Microscopy (SEM) technique for the characterisation of biological and non-biological samples at nano-scale level. Scanning Electron Microscopy has been around for a long while especially in material science laboratories in developed countries. The SEM has enabled scientist to have a better understanding of microstructure by providing unsurpassed optical magnifications of samples. In this introductory paper, we introduce the techniques of using SEM to capture highly magnified microstructure of a fly found on an African soybean (Glycine max) seed. We are able to estimate the number of lenses in each eye and zoom into features that could describe its life characteristics. Hexagonal lenses are estimated to have sizes ranging from 14 um to 19 um. This paper also presents a finding of a sea coral "pie like structure" on a single grain of sand used for water filtration.
Physical properties of GalnAsSb-based type-I quantum well 2.3&mu;m and 2.6&mu;m edge emit... more Physical properties of GalnAsSb-based type-I quantum well 2.3&mu;m and 2.6&mu;m edge emitting lasers are investigated using spontaneous emission and hydrostatic pressure techniques. Temperature dependence spontaneous emission analysis on GalnAsSb/AlGaAsSb (1.6%) compressively strained EEL emitting at 2.3pm shows that at least 81+-5% of the threshold current at room temperature is due to non-radiative recombination. It is also shown that Auger recombination (CHLH and/ or CHSH) is the dominating non-radiative process. It is also shown that non-pinning of the carrier density above threshold causes the external differential efficiency of these 2.3 &mu;m to decrease. There is also evidence of defect related recombination. For the 2.6&mu;m devices made of GalnAsSb/GaSb 1.7% compressively strained quantum well, at least 97+-2% of threshold at room temperature is due to non radiative recombination. It is also shown that Auger current is the dominant process. There is also evidence of hole leakage and defect current in the 2.6&mu;m EELs. T0 analysis show evidence of optical loss process suspected to be IVBA occurring which may couple the effects of non-pinning of the carrier density above threshold to cause the decreasing external differential efficiency observed in the devices. Investigation of GalnAsSb/AlGaAsSb 2.3&mu;m VCSELs shows that the gain peak and cavity mode are aligned at T~260+-10K. The analyses here suggest that for improved performance of the 2.3pm VCSEL, the gain peak should be shifted to higher energies by approximately 10meV. For the GalnAsSb/GaSb 2.6&mu;m VCSEL, the gain peak- cavity mode alignment is estimated to be at higher temperature (T=330+-10K) while the temperature insensitive region is obtained at T~200+-20K. It is estimated that by shifting the gain peak to higher energies (by approximately 8meV), the temperature insensitive region can be shifted to room temperature. Spontaneous emission analysis on 5 stage “W” interband cascade lasers (ICLs)show that at least 93+-2% of threshold current is due to non-radiative recombination. Pressure dependence of threshold current at 100K, 200K and 293K suggest that Auger recombination is the dominant loss process and is significant even at low temperatures. Considering the complex valence band structure of the “W” ICLs, it is possible that the CHLH Auger process is occurring even though the CHSH and CHCC are theoretically shown to be supressed. It is also shown that non-pinning of the carrier density above threshold causes the differential efficiency of the “W” ICL to decrease but IVBA may also be partly responsible
Journal of Data Analysis and Information Processing, 2021
The ability of machine learning techniques to make accurate predications is increasing. The aim o... more The ability of machine learning techniques to make accurate predications is increasing. The aim of this work is to apply machine learning techniques such as Support Vector Machine, Naïve Bayes, Decision Tree, Logistic Regression, and K-Nearest Neighbour algorithms to predict the shelf life of Okra. Predicting the shelf life of Okra is important because Okra becomes harmful for human consumption if consumed after its shelf life. Okra parameters such as weight loss, firmness, Titrable Acid, Total Soluble Solids, Vitamin C/Ascorbic acid content, and PH were used as inputs into these machine learning techniques. Support Vector Machine, Naïve Bayes and Decision Tree each accurately predicted the shelf life of Okra with accuracies of 100%. However, the Logistic Regression and K-Nearest Neighbour achieved 88.89% and 88.33% accuracies, respectively. These results showed that machine learning techniques especially Support Vector Machine, Naïve Bayes and Decision Tree can be effectively applied for the prediction of Okra shelf life.
IEEE Journal of Selected Topics in Quantum Electronics, 2017
The efficiency limiting mechanisms in type-I GaInAsSb-based quantum well (QW) lasers, emitting at... more The efficiency limiting mechanisms in type-I GaInAsSb-based quantum well (QW) lasers, emitting at 2.3, 2.6 and 2.9 µm, are investigated. Temperature characterization techniques and measurements under hydrostatic pressure identify an Auger process as the dominant nonradiative recombination mechanism in these devices. The results are supplemented with hydrostatic pressure measurements from three additional type-I GaInAsSb lasers, extending the wavelength range under investigation from 1.85 to 2.90 µm. Under hydrostatic pressure, contributions from the CHCC and CHSH Auger mechanisms to the threshold current density can be investigated separately. A simple model is used to fit the nonradiative component of the threshold current density, identifying the dominance of the different Auger losses across the wavelength range of operation. The CHCC mechanism is shown to be the dominant nonradiative process at longer wavelengths (> 2 µm). At shorter wavelengths (< 2 µm), the CHSH mechanism begins to dominate the threshold current, as the bandgap approaches resonance with the spin-orbit split-off band.
The success obtained from semiconductor laser devices is dependent on the science of manipulating... more The success obtained from semiconductor laser devices is dependent on the science of manipulating the electron-hole and the photon. While the most useful interaction in the laser is the recombination process that involves the electron and holes to produce a photon, other non-useful processes also occur and in some cases overshadow the preferred recombination process. In this review article, the physics behind radiative and non-radiative recombination processes and loss mechanisms dominant in quantum well semiconductor lasers is presented. The work concludes by suggesting possible solutions based on relevant published works
We present a Scanning Electron Microscopy (SEM) technique for the characterisation of biological ... more We present a Scanning Electron Microscopy (SEM) technique for the characterisation of biological and non-biological samples at nano-scale level. Scanning Electron Microscopy has been around for a long while especially in material science laboratories in developed countries. The SEM has enabled scientist to have a better understanding of microstructure by providing unsurpassed optical magnifications of samples. In this introductory paper, we introduce the techniques of using SEM to capture highly magnified microstructure of a fly found on an African soybean (Glycine max) seed. We are able to estimate the number of lenses in each eye and zoom into features that could describe its life characteristics. Hexagonal lenses are estimated to have sizes ranging from 14 um to 19 um. This paper also presents a finding of a sea coral "pie like structure" on a single grain of sand used for water filtration.
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