M. J. Siddiqui

An extensive study on simple and GRIN SCH-based In0.71Ga0.21Al0.08As/InP lasing heterostructures

In this paper, we have proposed a model for simple and graded index (GRIN) separate confinement heterostructure (SCH)-based In0.71Ga0.21Al0.08As/InP single-quantum-well lasing heterostructures and studied the energy band structure along with conduction and valence band envelope functions and band offsets. Under theoretical simulation, we have determined the behavior of quasi-Fermi levels in both the conduction and valence bands. Moreover, we have also calculated various important lasing characteristics and the optical gain of the lasing structure as a function of lasing wavelength in transverse electric (TE) and transverse magnetic (TM) modes. For both types of lasing structures, optical gain in the TE mode has been reported to be larger than that in the TM mode. In the TE mode the maximum optical gain for simple and GRIN structures has been achieved at lasing wavelengths of 1.55 and 1.38 μm, respectively, while in the TM mode the values of maximum optical gain for both types of the structures are found to be the same, i.e. at 1.34 μm. Since the optical attenuation within the waveguide is found to be minimum at 1.55 μm, the simple SCH-based In0.71Ga0.21Al0.08As/InP lasing structures are suggested to be preferred to the GRIN SCH-based lasing structures of InGaAlAs/InP material systems.

Quantum Well Width Effect on Intraband Optical Absorption in Type-II InAs/AlSb Nano-Scale Heterostructure

In this paper, we have studied theoretically the effect of width variation of quantum well on energy dispersion curves and transverse electric (TE) and transverse magnetic (TM) Intraband optical absorption coefficients in type-II InAs/AlSb nanoscale heterostructure by utilizing eight bands Kohn–Luttinger Hamiltonian. The outcomes of the calculations made in this work suggest that the optical absorption and transition energies can be enhanced by reducing the width of quantum well (active) region of the designed heterostructure. One more observation is that the polarization modes have no effect on the behaviour of change in transition energy with change in well width.

Carrier dependent gain characteristics of InGaP/GaAs nano-heterostructure

This paper reports the lasing characteristics of SCH based InGaP/GaAs nano-heterostructure such as anti-guiding factor (a substantial parameter for optical gain), material gain, mode gain, and carrier induced refractive index change. The simulation studies also cover the variation in material gain and mode gain with respect to lasing wavelength and photonic energy. Furthermore, gain calculations have also been reported for different carrier concentrations. The theoretical results achieved reveal that maximum gain of 2921.535 /cm appears at wavelength 0.625 μm and corresponding photonic energy is 1.98 eV. In addition, the analysis also shows that the proposed nano heterostructure provides more optical gain in TE polarization mode than TM mode. A significant gain achieved at lasing wavelength promises the utility of proposed structure in optical fibre communication systems.

Gain investigation on strained InGaA1As/InP lasing nano-heterostructure

In this paper we have reported various lasing characteristics of strained InGaAlAs/InP nano-heterostructure. Under the effect of strain, behavior of material gain with lasing wavelength and current density has been studied and reported. In addition, differential gain and refractive index change with carriers has also been calculated. The maximum material gain for compressive strained heterostructure appears at the wavelength of 1.55 μm while for tensile strained heterostructure, it appears at the wavelength of 1.70 μm, The achieved results show that compressive strained structure is very important in the optical fiber based communication systems due to low attenuation.

Modeling and simulation of AlGaAs/GaAs SQW laser for optical communication system

This paper aims to report various lasing characteristics of AlGaAs/GaAs single quantum well laser for optical communication systems. Under modeling and mathematical simulation, we have calculated anti-guiding factor, gain compression, differential gain, peak material gain as a function of carrier density, and convolution optical gain of AlGaAs/GaAs SQW laser as function of wavelength and photonic energy. On behalf of calculations, we have shown that the modeled SQW laser has maximum optical gain at ∼ 0.83 µm. The results obtained ensure the usefulness of the AlGaAs/GaAs SQW SCH laser in communication systems based on optical fiber.

Optimization of d-doped AlInAs/InGaAs HEMT performance using spacer layer and d-doping

In this paper efforts have been made to optimize the performance of delta (δ) doped 0.5 µm gate length InP based In<inf>0.53</inf>Ga<inf>0.47</inf>As/In<inf>0.52</inf>Al<inf>0.48</inf>As high electron mobility transistor with the help of some parameters as δ-doping and spacer layer thickness variation. We perform characterization studies on high density two-dimensional electron gas (2DEG), conduction band discontinuity (ΔEC), threshold voltage (V<inf>th</inf>), transconductance (g<inf>m</inf>), cut-off frequency (f<inf>T</inf>), confined in lattice-matched InP based d-doped In<inf>0.53</inf>Ga<inf>0.47</inf>As/In<inf>0.52</inf>Al<inf>0.48</inf>As quantum wells HEMT grown by molecular beam epitaxy (MBE) on InP substrate. The impact of parameters (δ doping and spacer layer) variation on the conduction band discontinuity, high density 2DEG and optimization of the performance of HEMT has been analysed. These values then utilize to optimize figure of merit such as transconductance and cut-off frequency of device.