Polarization bistability of vertical cavity lasers under external optical injection

The polarization bistability of VCLs is studied theoretically with the consideration of dielectric Bragg reflectors, surface coatings, carrier induced refractive index inside the active layer as well as the intensity and wavelength of the injected light. The VCL has a built-in index guided structure and a GaAs-Al0.3Ga0.7As quantum well active layer. A rate-equation model is developed. It is shown that all-optical switching and memory operation can be achieved in VCLs by external optical injection, however, devices with suitable design of surface coating and Bragg reflectors are required.published_or_final_versio

Dynamic behavior of vertical-cavity surface-emitting lasers

A quasi-three-dimensional dynamic model of index-guided vertical-cavity surface-emitting lasers is developed. Detailed structure of Bragg reflectors and lateral optical confinement are considered into the model. A three-dimensional waveguide problem is reduced to one dimension by using the effective-index method. The dynamic response of optical field is solved by the time-domain algorithm. In addition, the lateral variation of carrier concentration, refractive index, and spontaneous-emission profile are also determined in a self consistent manner. Using this model, the influence of carrier transport and hot carriers on the dynamic behavior of vertical-cavity surface emitting lasers is studied. It is found that these nonlinearities have significant influence on the relaxation-oscillation frequency and modulation bandwidth of the devices.published_or_final_versio

Theoretical analysis of polarization bistability in vertical cavity surface emitting semiconductor lasers

The polarization bistability of vertical cavity surface emitting lasers under external optical injection is analyzed theoretically. It is found that on the condition where the optical gain is blue-shifted relative to the cavity mode, the bistable characteristics of VCSEL's can be improved significantly: (1) low optical power of the external injection light is required, (2) the influence of self-heating effects is minimized, and (3) wide bistable hysteresis loop width can be maintained. Furthermore, it is also shown that the reflectivity of Bragg reflectors should also be optimized to improve the performance of VCSEL's as bistable switches.published_or_final_versio

Double-tapered-waveguide distributed feedback lasers for high-power single-mode operation

Theoretical analysis of double-tapered-waveguide distributed feedback semiconductor laser for stable single-mode and high-power operation is presented. It is found that the single-mode behavior of a distributed feedback laser with large coupling-length product can be improved significantly by the double-tapered-waveguide structure.published_or_final_versio

An improved time-domain traveling-wave model for vertical-cavity surface-emitting lasers

The use of the time-dependent transfer matrix and wide-angle beam propagation method is proposed to improve the computational speed and accuracy of a recently developed time-domain traveling-wave model of vertical-cavity surface-emitting lasers. With suitable utilization of the transfer matrix, significant reduction of the total execution time of the traveling-wave model can be obtained. In addition, the use of the wide-angle beam propagation method can minimize the calculation error of the traveling-wave model due to the diffraction of light from the small aperture of the laser cavity.published_or_final_versio

A quasi-three-dimensional large-signal dynamic model of distributed feedback lasers

A simple, but powerful, quasi-three-dimensional large-signal dynamic model of distributed feedback semiconductor laser is presented. The transient response of lasers is analyzed by using a combined beam propagation method and time-domain algorithm that is capable of including the longitudinal and lateral variation of the optical-mode and carrier density profiles. In addition, the spontaneous emission noise, the nonuniform current injection resulting from the variation of Fermi-voltage as well as that of the refractive index distribution are also taken into consideration. Using this model, the influence of nonuniform waveguide structure on the static and dynamic responses of distributed feedback lasers is analyzed. In addition, a novel double tapered waveguide distributed feedback laser is proposed for stable single-mode operation at high power.published_or_final_versio

Enhancement of mode stability in vertical cavity surface emitting lasers with diffused quantum wells structure

The use of diffused quantum well structures to enhance single transverse mode operation in vertical cavity surface emitting GaAs-AlGaAs QW semiconductor lasers is proposed and analyzed theoretically.published_or_final_versio

Semiconductor lasers using diffused quantum-well structures

We assess the relative merits and prospects of using diffused quantum-well (QW) structures in semiconductor lasers. First, different techniques to achieve interdiffusion are analyzed and compared. Second, recent development of semiconductor lasers using interdiffusion technique is also discussed. Third, the optical properties of diffused QWs are studied. In addition, novel design of diffused QWs structures to maintain stable single-mode operation in semiconductor lasers is proposed. Finally, brief discussion and conclusion are given.published_or_final_versio

Single mode operation of impurity-induced disordering large area vertical cavity surface emitting lasers

Vertical-cavity surface-emitting lasers (VCSELs) with suitable interdiffusion quantum wells profile by the use of selective impurity-induced disordering is proposed for high power single mode operation in large area devices. It is shown that the transverse optical confinement in the quantum well active region formed by the diffusion profile counteracts the influence of carrier spatial hole burning for VCSELs biased at high injection current. Results indicate that a single mode operation can be maintained in VCSELs with the diameter of core region equal to 50µm.published_or_final_versio

Identifying smart design attributes for Industry 4.0 customization using a clustering Genetic Algorithm

Industry 4.0 aims at achieving mass customization at a mass production cost. A key component to realizing this is accurate prediction of customer needs and wants, which is however a challenging issue due to the lack of smart analytics tools. This paper investigates this issue in depth and then develops a predictive analytic framework for integrating cloud computing, big data analysis, business informatics, communication technologies, and digital industrial production systems. Computational intelligence in the form of a cluster k-means approach is used to manage relevant big data for feeding potential customer needs and wants to smart designs for targeted productivity and customized mass production. The identification of patterns from big data is achieved with cluster k-means and with the selection of optimal attributes using genetic algorithms. A car customization case study shows how it may be applied and where to assign new clusters with growing knowledge of customer needs and wants. This approach offer a number of features suitable to smart design in realizing Industry 4.0