| High power single-transverse-mode vertical cavity surface emitting lasers are desirable for a number of purposes, including 980/1480nm pump source for Erbium doped amplifiers and in communications systems. The highest power achieved from such a device currently is less than 5mW due to small device size. We investigate two different methods for achieving single-transverse-mode operation from medium sized vertical cavity surface emitting lasers to increase the lasing power.; Using an external cavity setup, we use far-field filtering techniques to apply modal discrimination to the higher order modes in the device. Since the higher order modes have a higher divergence and hence more power farther from the beam axis spatially, an aperture placed in the far-field accomplishes this purpose. We incorporate the necessary optics, which comprise a collimating lens, an on axis aperture, and an output coupler, into one optical component in the form of a GRIN rod lens with an apertured reflector deposited on its output endface. With this setup, we obtained a record single-transverse-mode output power of 4.5mW.; We have also designed and fabricated a single-transverse-mode vertical cavity surface emitting laser utilizing a novel concept which creates an index guide, within the device top mirror, by trapping free carriers through hydrogen ion implantation within a circular region of given size. The removal of free carriers causes an increase in refractive index, creating a waveguide. Using fiber optics theory the waveguide is designed to be single mode for a given size by choosing the correct index difference between the cladding and the core, which then sets the doping level in the top mirror.; The devices designed using this concept displayed single-mode behavior up to 1.7*Ith, whereas a typical device of the same size was multi-mode just above threshold. The results were obtained under pulsed current drive due to material with high threshold current densities. Future work includes fabricating and testing devices with higher quality material to obtain results under continuous current drive, and adjusting the doping levels and hydrogen ion implantation energies and doses to optimize the waveguide. |
