Lateral Waveguiding Properties of VCSELs for Integrated Optical Monitoring

We have investigated experimentally the optical behaviour of a Vertical-Cavity Surface-Emitting Lasers (VCSEL) when it is used as a lateral waveguide. This provides a better understanding of the mechanisms involved in VCSEL optical power monitoring by integrated lateral detection. The lateral optical spectra as well as the waveguide transmission spectrum have been measured. Their analysis and comparison demonstrate that the lateral signal is mostly coming from the spontaneous emission escaping laterally from the VCSEL and that light is filtered during the propagation and detection processes. This allows us to explain previous results obtained in two different configurations of lateral detection. These results are useful to optimize the lateral detection performances for concrete applications in monitoring or telemetry systems.