F. Rahman

INVESTIGATION OF MATERIAL GAIN OF In0.90Ga0.10As0.59P0.41/InP LASING NANO-HETEROSTRUCTURE

In this paper, we have proposed a step separate confinement heterostructure (SCH) based lasing nano-heterostructure In0.90Ga0.10As0.59P0.41/InP consisting of single quantum well (SQW) and investigated material gain theoretically within TE and TM polarization modes. In addition, the quasi Fermi levels in the conduction and valence bands along with other lasing characteristics like anti-guiding factor, refractive index change with carrier density and differential gain have also been investigated and reported. Moreover, the behavior of quasi Fermi levels in respective bands has also been correlated with the material gain. Strain dependent study on material gain and refractive index change has also been reported. Interestingly, strain has been reported to play a very important role in shifting the lasing wavelength of TE mode to TM mode. The results investigated in the work suggest that the proposed unstrained nano-heterostructure is very suitable as a source for optical fiber based communication systems due to its lasing wavelengths achieved at ~1.35 μm within TM mode, while ~1.40 μm within TE mode.

Qualitative analysis of gain spectra of InGaAlAs/InP lasing nano-heterostructure

This paper deals with the studies of lasing characteristics along with the gain spectra of compressively strained and step SCH based In0.71Ga0.21Al0.08As/InP lasing nano-heterostructure within TE polarization mode, taking into account the variation in well width of the single quantum well of the nano-heterostructure. In addition, the compressive conduction and valence bands dispersion profiles for quantum well of the material composition In0.71Ga0.21Al0.08As at temperature 300 K and strain ~1.12% have been studied using 4 × 4 Luttinger Hamiltonian. For the proposed nano-heterostructure, the quantum well width dependence of differential gain, refractive index change and relaxation oscillation frequency with current density have been studied. Moreover, the G–J characteristics of the nano-heterostructure at different well widths have also been investigated, that provided significant information about threshold current density, threshold gain and transparency current density. The results obtained in the study of nano-heterostructure suggest that the gain and relaxation oscillation frequency both are decreased with increasing quantum well width but the required lasing wavelength is found to shift towards higher values. On behalf of qualitative analysis of the structure, the well width of 6 nm is found more suitable for lasing action at the wavelength of 1.55 μm due to minimum optical attenuation and minimum dispersion within the waveguide. The results achieved are, therefore, very important in the emerging area of nano-optoelectronics.

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.

Strain profile in GaN/AlGaN nano-heterostructure

The variations in the strain with different material compositions in the model of GaN/AlGaN heterostructure have been reported. The significant strain produced due to lattice mismatch at the interface of thin epitaxial layers in the structure has been observed only in the quantum region that lies between 100 nm and 188 nm. Moreover, the strain in the quantum region is found to be tensile along both x and y directions, but compressive in nature along z-direction.

Modal gain study for SQW and MQWs based nano-heterostructures

This paper reports the behavior of modal gain versus current density for single quantum well (SQW) and multiple quantum wells (MQWs) based lasing nano-heterostructures of InGaAlAs/InP with in TE mode. The model is based on simple separate confinement heterostructure (SCH). In general, the modal gain has been found to increase with increase in current density. Moreover, less threshold current density is required for SQW but for MQWs, a very high threshold current density is required. The results obtained in the simulation of hetero structures suggest that maximum gain with high quality lasing beam appears at the wavelength of 1.55 μm. The achieved wavelength gives a minimum optical attenuation in the optical fiber communication systems.