Design, growth and characterization of a semiconductor membrane laser gain structure with broadband emission in the 720-760 nm wavelength range
Rajala, Patrik (2020)
2020
Teknis-luonnontieteellinen DI-ohjelma - Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2020-10-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202010087260
https://urn.fi/URN:NBN:fi:tuni-202010087260
Tiivistelmä
Membrane external-cavity surface-emitting lasers (MECSEL) represent the newest advancements when it comes to vertically emitting semiconductor lasers, and they offer various new possibilities to the design and performance of this subgroup of semiconductor lasers. While known for their great beam properties, relatively high emission powers, power scalability, stability and reliability, vertically emitting lasers have not been reported to have particularly high tuning ranges, even though this is a highly desired feature of e.g. solid state lasers.
In this study, a MECSEL structure for very broadband emission in the yet unreported wavelength range of 720-760 nm is first designed, then epitaxially grown and finally characterized. To achieve this, deep understanding of the prerequisites for both lasing and epitaxial growth is required and thus the most important aspects of the physical background concerning the topic are first presented. The main emphasis in the design phase was on the simulation of the energy band structure, electric field inside the structure during operation and strain induced by the structure with three kinds of quantum wells in a single MECSEL structure. In the growth phase the focus was on the growth of quaternary GaInAsP quantum wells with molecular beam epitaxy, while the characterization phase emphasized the evaluation of the quality of the epitaxially grown membrane. In addition to these phases, the structures grown were also tested in a laser setup to assess the quality and viability of the MECSEL’s design.
At best a tuning range of 14.1 THz from 717 nm to 742 nm with maximum output power of 0.2 W was demonstrated. While the tuning range presented was not particularly wide, strong evidence in the form of additional lasing measurements as well as photoluminescence measurements was given to support the design solution of using several different kinds of quantum wells in a single MECSEL structure to reach high emission bandwidths in the future. Several possibilites and points of interest, particularly to increase both the emission bandwidth and emission power with future gain structures, were identified and presented. Laser emission on as short a wavelength as 715 nm from a vertically emitting laser utilizing quantum wells was also presented, which was unreported prior to this study. A process of physically stacking MECSELs and using them as gain amplifying medium, as well as lasing results demonstrating the viability of this process, were also presented for the first time.
In this study, a MECSEL structure for very broadband emission in the yet unreported wavelength range of 720-760 nm is first designed, then epitaxially grown and finally characterized. To achieve this, deep understanding of the prerequisites for both lasing and epitaxial growth is required and thus the most important aspects of the physical background concerning the topic are first presented. The main emphasis in the design phase was on the simulation of the energy band structure, electric field inside the structure during operation and strain induced by the structure with three kinds of quantum wells in a single MECSEL structure. In the growth phase the focus was on the growth of quaternary GaInAsP quantum wells with molecular beam epitaxy, while the characterization phase emphasized the evaluation of the quality of the epitaxially grown membrane. In addition to these phases, the structures grown were also tested in a laser setup to assess the quality and viability of the MECSEL’s design.
At best a tuning range of 14.1 THz from 717 nm to 742 nm with maximum output power of 0.2 W was demonstrated. While the tuning range presented was not particularly wide, strong evidence in the form of additional lasing measurements as well as photoluminescence measurements was given to support the design solution of using several different kinds of quantum wells in a single MECSEL structure to reach high emission bandwidths in the future. Several possibilites and points of interest, particularly to increase both the emission bandwidth and emission power with future gain structures, were identified and presented. Laser emission on as short a wavelength as 715 nm from a vertically emitting laser utilizing quantum wells was also presented, which was unreported prior to this study. A process of physically stacking MECSELs and using them as gain amplifying medium, as well as lasing results demonstrating the viability of this process, were also presented for the first time.