High-speed visible VCSEL for POF data links

We report on two AlGaInP-based visible VCSEL designs based on different current confinement schemes, ion implantation and selective oxidation, and we compare the respective performances with a particular interest on the modulation properties. The implanted device operated continuous wave (CW) up to 40 degrees Celsius. Threshold current of 7 mA, threshold voltage of 2.5 V and maximum optical power of 0.3 mW were measured at room temperature. The small signal modulation responses were fitted using a 3-poles model, allowing the estimation of various parameters such as resonance frequency, damping factor and parasitic cut-off. The maximum 3dB- bandwidth was shown to be 2.1 GHz, limited both by thermal and parasitic effects. 'Error-free' transmission at 1 Gb/s was demonstrated through 50-meter of graded-index POF. The selectivity oxidized devices achieve much higher output power (1.8 mW for the 10 micrometer opening diameter) with threshold current as low a 1.5 mA and threshold voltage of 2.1 V at room temperature, and operate CW up to 49 degrees Celsius. The maximum 3 dB-bandwidth was 4.5 GHz. Modulation current efficiency factor up to 2.8 GHz/(root)[mA] was measured.