Power scaling and thermal lensing in 825 nm emitting membrane external-cavity surface-emitting lasers

We present a membrane external-cavity surface-emitting laser (MECSEL) operating around 825 nm at room temperature. With a tuning range of 22 nm, the MECSEL fills the spectral gap between 810 nm and 830 nm, and extends the wavelength coverage of this category of high beam quality semiconductor lasers. For high power operation, the pump spot size and cavity mode size can be enlarged in MECSELs. We apply this technique and demonstrate power scaling. The maximum output power is increased from 0.7 W to 1.4 W. Investigations on the beam quality reveal thermal lensing with a marginally changing M² value close to the diffraction limit.