Simulating laser diodes saves time, money

WORLDWIDE--Can meticulously researched and many-layered physics-simulation software developed over a period of many years in academia be of any use in the commercial world? If the physics is related to semiconductor-laser operation, and the software allows a laser manufacturer to reduce the number of steps in designing and developing a new laser diode, the software can be very useful indeed.

Jun 1st, 2009

WORLDWIDE--Can meticulously researched and many-layered physics-simulation software developed over a period of many years in academia be of any use in the commercial world? If the physics is related to semiconductor-laser operation, and the software allows a laser manufacturer to reduce the number of steps in designing and developing a new laser diode, the software can be very useful indeed.

Simulase, a software package introduced by Nonlinear Control Strategies (NLCSTR; Tucson, AZ) is quite a bit more intricate than the laser-diode modeling software that most laser engineers are used to; one reason is that it is the summation of 15 years of research at institutions such as the College of Optical Sciences at the University of Arizona and Philipps Universität at Marburg.

Jörg Hader, senior scientist at NLCSTR and an associate research professor at the University of Arizona, describes the need for software complexity in the design of semiconductor emitters. “The processes that determine the light generation in a semiconductor are microscopic interactions between electrons and photons. Because there is an incredibly high number of electrons present in the semiconductor and all are interacting with each other as well as with the surrounding lattice (phonons) and photons, these processes are complicated microscopic many-body interactions,” he says. Existing commercial software models macroscopic heat, carrier and light dynamics; however, describing the generation (or loss) of light in the laser’s active region has been done only at a general level, he notes.

If a working device needs to be optimized, the engineer will simply change some small aspect of the original design; this will cost very little. But to develop a truly optimized device or a fairly new design, these steps generally have to be repeated multiple times; as a result, the costs can multiply by 5 to 20 times, Hader explains.

“Quite often, one has to grow several test samples to adjust the growth conditions in order to really hit the design specs,” he says. For a complicated structure like a VECSEL--which might require diamond heat spreaders, heat sinks, and possibly antireflection coatings--this can take a technician days before even the first growth of the complete structure can be attempted.

The new software cuts down these iterations by telling the engineer how quantitatively correct the crucial aspects of the proposed device will be, including lasing wavelength, threshold, tuning, and so on. Its abilities have been verified by taking existing complex semiconductor-laser designs, entering their parameters into the software, and confirming that the simulation matches the actual laser performance, all without iteration.

--John Wallace


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