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Anand Gopinath, Associate Fellow

Modeling of Vertical Cavity Lasers and Integrated Optical Circuits

The Vertical Cavity Surface Emitting Laser (VCSEL) is one of the new laser structures developed in the past ten years. The great advantage of this structure is that standard microelectronics techniques may be used to fabricate the device, and expensive cleaving of the crystals and alignment of the facets normal to cleave planes are avoided. The disadvantage of these devices is that devices with diameters of the order of 10 mm and larger quickly become multimode, and the spectrum of emission has many lines. These researchers are conducting an experimental project to find means of keeping these devices single model for all diameter sizes. To perform this project, these devices need to be modeled in considerable detail, and to this end, these researchers are in the process of writing a vector wave solver in the cylindrical coordinates, a code has already been written for current flow in p-i-n diodes, and this is being extended for the heterostructure diodes and will be extended to the cylindrical geometry. A heat flow code has also been written, and this needs to be extended to the cylindrical geometry. These are now being put together for a self consistent VCSEL model.

In this project, these researchers are using vector edge elements in the cylindrical r-z geometry with rotational symmetry. Current plans are for the f variation in the form of ejmf, with m = 0, 1, 2, . . . The x-y edge element code has been written and is being debugged. These researchers are now converting this to the cylindrical geometry. A version of the temperature calculations of the VCSEL has already been written in Cartesian coordinates and needs to be converted to the cylindrical coordinate system. These researchers have also written a kp code for calculating the gain of quantum well structures with and without strain, and this is used to calculate the gain of the wells with current drive. The rate equations need to be rewritten since the earlier version had convergence problems. These researchers are now putting all these programs together to run a self-consistent solver for the VCSEL. However, considerable time has to be spent getting all these programs to work together.

Further work is investigating integrated optics. This project includes integrated switch structures using semiconductor laser amplifiers as the switch elements, integrated semiconductor laser amplifiers Faraday rotation isolator, dielectric waveguide amplifiers, and dielectric waveguide amplified spontaneous emission sources. All these devices require waveguide mode solvers, with and without gain/loss, and in the case of the Faraday rotation isolator, anisotropic media. For this purpose, the x-y finite element code has been written and is being extended to cover most cases.

This information is available in alternative formats upon request by individuals with disabilities. Please send email to alt-format@msi.umn.edu or call 612-624-0528.

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