Optically pumped semiconductor (OPS) vertical external-cavity surface-emitting lasers (VECSELs) are an important category of power scalable lasers with a wide range of applications in bio photonics, medicine technologies and for example spectroscopy. The possibility of band-gap engineering, a laser emission in the fundamental Gaussian mode and the technical simplicity leads to ongoing growth of the area of applications for these tunable laser sources. The open laser resonator allows inserting frequency selective and converting intra-cavity elements as well as absorptive elements to create mode locking. In addition, intra cavity gas cells allow absorption spectroscopy. Aiming on spectroscopic applications for rubidium one important absorption line is located at 780 nm. Nowadays, laser emission in this spectral range has not been shown by VECSELs, neither in direct nor in frequency doubled emission although the available III-V semiconductor materials would provide such a band-gap. A very low charge carrier confinement may be the main challenge here.
We present several strategies to create gain structures based on the AlGaAs- and the AlGaAs/AlGaInP material system. The expected high thermal sensitivity can be counteracted by realizing this VECSEL structure also as a membrane external-cavity surface-emitting laser (MECSEL) to improve the heat transfer out of the active region. Investigations comparing barrier pumping with in-well pumping are also possible. A MECSEL would be in both cases beneficial here as not absorbed pump light is just transmitted instead of being absorbed in the DBR creating unnecessary heat.
Hermann Kahle, Kostiantyn Nechay, Jussi-Pekka Penttinen, Antti Tukiainen, Sanna Ranta, and Mircea Guina, "MECSELs and VECSELs for rubidium spectroscopy with direct emission around 780 nm (Conference Presentation)," Proc. SPIE 10515, Vertical External Cavity Surface Emitting Lasers (VECSELs) VIII, 105150A (Presented at SPIE LASE: January 29, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2290307.5751425832001.
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