Unlike a VCSEL, in which two mirrors are incorporated in the chip’s layers to form the optical cavity, in a VECSEL (Vertical External-Cavity Surface Emitting Laser) one of the two mirrors is external to the stack structure. As a result, the cavity includes a free-space region typically about 1 cm. This arrangement allows a larger area of the device to be pumped and therefore more power can be extracted – as much as 30 W. The external cavity also allows intracavity techniques such as frequency doubling, single frequency operation and femtosecond pulse mode-locking.
The results presented in this short article has been obtained by the ‘Institut d’Electronique du Sud’ (IES). The high-rate capability of the ZOOM Spectra laser spectrum analyzer allowed the IES to observe a phenomenon that lasts less than 1 millisecond on a 0.5 nm spectral range at the starting of a VECSEL emitting around 1010 nm.
After the start of the driver current, the laser spectrum is measured over time at high rate. A monotonic increase of the wavelength with several regular hopping modes is observed, combined with an increase of the emitted power. The spectrum is stationary after 0.5 µs. This results on a combination of the lasing effect start and the thermal stabilization of the micro-chip.