04 Aug 2008 Polflips, which cause sudden power failure in some laser pulses, disturb spectroscopic measurements. This effect is essentially due to the high amount of symmetry in the SM VCSEL; the polarization state is unstable. As a result, the symmetry has to be broken. The additional application of a "subwavelength grating" on the output coupler mirror was successfully implemented by the scientists at ULM-Photonics. As a result only one polarization direction can resonate. This means that the polarization is stabilized by the design, but unfortunately not defined. Such polarization stabilized SM VCSELs are available at 850 nm. |
