Effect of carriers on the optical properties of AlGaAs/GaAs interdiffused quantum well lasers

The carrier-induced effects in the change of refractive index on the GaAs/AlWGa1-W as square quantum well (SqQw) and diffused quantum well (DFQW) was investigated. Band-filling, bandgap shrinkage, and free- carrier absorption were included. Carrier concentrations from 1016 to 1018 cm-3 were considered. The energy levels and their associated wavefunctions in the SqQW or DFQW structures are calculated by solving both the Schroedinger and the Poisson equations self-consistently. It is followed by the absorption change, which is defined as the difference between the absorption coefficient with carrier injection in QW and that without carrier injection. The refractive index change can be obtained by applying Kramers-Kronig Transformation. These results obtained are useful in the design of devices, such as lasers, optical phase, modulators and switches. Thus, it is important to know the carrier-induced energy shift in GaAs/AlWGa$_1-W) as quantum well structures.published_or_final_versio

The effect of interdiffusion on the intersubband optical propertiesin a modulation-doped quantum-well structure

The linear and nonlinear (based on optical field intensity) intersubband absorptions in conduction band, and its change in refractive index in AlGaAs-GaAs interdiffused quantum wells (QWs) are presented. The calculation of the electron energy levels and the envelope wave functions in a modulation doped interdiffused QWs with screening effects are considered. QW interdiffusion shows a wavelength tunability of the intersubband absorption peaks and refractive index dispersions. This shifting of the transition energies is also demonstrated here to be a useful technique for broad-band and multicolor photodetector application. In addition, it can serve to remove noise, such as minor peaks and dispersions, in the optical spectra.published_or_final_versio

Quantum well intermixing for photonic IC applications

Photonic IC is an attractive information processing means to fully utilize the enormous bandwidth carried by the optical signals. The full integration of photonics devices, such as tunable lasers, modulators and photodetectors have to be developed and which can be obtain by using the Quantum Well Intermixing technology. This paper will explore on the wavelength tunability using different Quantum Well Intermixing techniques, such as impurity induced diffusion and impurity-free vacancy diffusion. Emphasis will be put on the development of very recent innovations and applications.published_or_final_versio

Advances in intermixed quantum well devices

Quantum well composition intermixing is a thermal induced interdiffusion of the constituent atoms through the hetero-interface. The intermixed structures created by both impurity induced and impurity free or vacancy promoted processes have recently attracted high attention. The interdiffusion mechanism is no longer confined to a single phase diffusion for two constituent atoms, but it can now consist of two or multiple phases and/or multiple species, such as three cations interdiffusion and two pairs of cation-anion interdiffusion. A review on the impact of intermixing on device physics is presented with many interesting features. For instance, both compressive or tensile strain materials and both blue or red shifts in the bandgap can be achieved depending on the types of intermixing. The recent advancement in intermixing modified optical properties, such as absorption, refractive index as well as electro-optic effects are discussed. In addition, this paper places a strong emphasis on the device application of the intermixing technology. The advantage of being able to tune the material provides a way to improve the performance of photodetectors and modulators. Attractive distributed-feedback and vertical cavity laser dynamics have been shown due to some unique device physics of the quantum well intermixing. Several state-of-the-art results will be summarized with an emphasis on its future development and directions.published_or_final_versio

Refractive index of interdiffused AlGaAs/GaAs quantum well

A model is developed for the polarization dependent refractive index of interdiffused AlGaAs/GaAs quantum well at room temperature for wavelengths ranging from 0.6 to 2 µm. The present model is based on a semianalytic and semiempirical method through the Kramers–Krönig transformation. The multi-quantum-well structures, including the exciton effect and above barrier gap contributions, are fully considered in this model. The distinct structures at energies of the E0,E0 + 0,E1, and E2 critical points are revealed. Moreover, the birefringence at room temperature is also analyzed in the wavelength range varying from 0.7 to 1.0 µm. The calculated refractive index results are in satisfactory agreement with the experimental measurements over the quantum well band edge, i.e., 0.8–0.9 µm. The effect of interdiffusion on the change of refractive index is discussed. The polarization dependent absorption coefficients are also calculated with all the bound excitons, and results agree well with experiments. These results are important, since refraction index in a particular wavelength region of interest, where experimental data are not available, can be determined and thus are very useful in the design of devices. ©1997 American Institute of Physics.published_or_final_versio

Optical properties of an InGaAs-InP interdiffused quantum well

A comprehensive model is developed for the calculation of polarization-dependent absorption coefficients and refractive index of the InGaAs-InP interdiffused multiple-quantum-well at room temperature for wavelengths ranging from 1.1 to 2.4 μm. Groups III and V types of interdiffusion are considered separately. The as-grown structure is a latticed-matched In0.53Ga0.47As-InP structure with a well width of 60 Å. The optical transitions consist of a full quantum-well calculation together with Γ,X, and L valleys contributions and through the Kramers-Kronig transformation to link the real and imaginary parts of the dielectric functions. The results show that group-III-only interdiffusion produces compressive strain and results in a band-edge red shift and refractive index enlargement, while the tensile strain induced by group-V-only interdiffusion results in a vice verse effect. This provides a left and right tunable band edge and positive and negative index steps dependent on the interdiffusion process. A small and constant birefringence of 0.005 at around 1.55 μm can also be obtained over a 50-nm wavelength range by using group-V-only interdiffusion. These properties have strong implications in realizing a tunable and high-performance device as well as for photonic integrations.published_or_final_versio

Interdiffused as a means of fabricating parabolic quantum wells for the enhancement of the non-linear third order susceptibility by triple resonance

Interdiffusion of a standard AlGaAs/GaAs quantum well is proposed as a viable alternative to the complex techniques necessary to fabricate parabolic quantum wells. The extent of the linear diffusion is optimized in order to produce an energy-level ladder if four almost equally spaced eigenstates. The calculated third-order susceptibility of 2700 (nm/V)2 is comparable with that of the parabolic quantum well, which is more than six orders of magnitude compared to that of the bulk GaAs. ©1996 American Institute of Physicspublished_or_final_versio

Quantum well intermixing: materials modeling and device physics

Quantum well composition intermixing is a thermal induced interdiffusion of the constituent atoms through the heterointerface. The intermixed structures created by both impurity induced and impurity free or vacancy promoted processes have recently attracted high attention. The interdiffusion mechanism is no longer confined to a single phase diffusion for two constituent atoms, but it can now consist of two or multiple phases and/or for multiple species, such as three cations interdiffusion and two pairs of cation-anion interdiffusion. A review on the impact of intermixing on device physics is presented with many interesting features. For instance, both compressive or tensile strain materials and both blue or red shifts in the bandgap can be achieved depending on the types of intermixing. The recent advancement in intermixing modified optical properties, such as absorption, refractive index as well as electro-optics effects are discussed. In addition, this paper will place a strong emphasis on the device application of the intermixing technology. The advantage of being able to tune the material provides a way to improve the performance of photodetectors and modulators. Attractive distributed-feedback and vertical cavity laser dynamics have been shown due to some unique device physics of the quantum well intermixing. Several state-of-the-art results will be summarized with an emphasis on its future development and directions.published_or_final_versio

Single versus double ion implantation defined AlGaAs/GaAs quantumwell waveguide

The purpose of this work is to investigate ion implantations on a two-dimensional optical waveguide structure. The waveguide structure, to be analyzed here consists of an AlGaAs-GaAs MQW on a thick AlGaAs buffer layer.published_or_final_versio