Proposed enhancement of side-mode suppression ratio in /spl lambda//4 shifted distributed feedback lasers with nonuniform diffused quantum wells

Abstract

An enhancement of the side mode suppression ratio, by utilizing interdiffused quantum wells, of a X/4 shifted distributed feedback laser is demonstrated theoretically. It is found that by introducing a diffusion step along the longitudinal direction of the quantum-well active region, the suppression ratio can be improved significantly for large nL (>2.6) devices. The maxim~m power for single longitudinal mode operation is increased by more than 50 mW.

Comprehensive modeling of diffused quantum-well vertical-cavity surface-emitting lasers

“…The ions diffuse thermally into the active layer due to the concentration gradient. The annealing process can be described by the diffusion equation given as follows: (2) where is the impurity concentration and ( 10 cm s ) is the diffusion coefficient of the impurity at a specific annealing temperature. It is assumed that no impurity is escaped from the device to the surrounding such that the corresponding boundary conditions are given by 1) at the edge of the device;…”

“…If is assumed to be time independent, and its derivatives can be determined and utilized as the constant coefficients of (6). Hence, in (6) can be solved numerically as if in (2). The extent of interdiffusion inside the QW active layer is characterized by a diffusion length defined as 7where is the well width, is the initial concentration of indium and is the annealing time.…”

“…Recently, Fabry-Pérot and distributed feedback (DFB) semiconductor lasers with diffused QW's structures have been proposed for high-power single-longitudinal-mode operation [2], [3]. This is because the longitudinal distribution of refractive index inside the laser cavities can be varied by the interdiffusion technique.…”

“…In this paper, a comprehensive numerical model to analyze the influence of interdiffusion on the steady static performance of VCSEL is presented. One major advantage of this model over the previous works [2]- [5] is the consideration of the implanted ions profile inside the laser cavity after rapid thermal annealing. Hence, the nonuniform distribution of electrical conductivity and absorption loss can be evaluated.…”

Theoretical analysis of diffused quantum-well lasers and optical amplifiers

“…The calculated bandgap energy of DFQW is also a crucial parameter for optimizing the operation wavelength, particularly for those optical devices that are sensitive to the absorption edge such as waveguide-type electroabsorption modulators, photodetectors and passive waveguides. Recently, some interesting Fabry-Perot and distributed feedback (DFB) laser structures using DFQW have been proposed [17], [18], even though there is no experimental demonstration due to the complexity of the proposed structures.…”