Abstract

Long-wavelength tunable vertical-cavity surface-emitting lasers (VCSELs) are finding their way into applications like optical fiber communications and spectroscopy where spectral purity and a narrow laser linewidth Δν are particularly important. However, mechanical thennal noise, i.e. Brownian motion of the micro-electro-mechanical system (MEMS), has been reported to add a significant contribution to the linewidth of [1] electro-statically tunable (Δν>lGHz, without feedback) and [2] optically pumped (Δν>200MHz) MEMS VCSELs. We report the linewidth of a hybrid MEMS VCSEL combining an InP-based active component incorporating 7 InGaAlAs quantum wells and a buried tunnel junction (BTJ, Ø =10μm) and a concave AlGaAs/GaAs MEMS DBR with electro-thermal actuation for broadband wavelength tuning up to 60mn around 1.55μm. We equipped the VCSEL with comparatively heavy and stiff (compressively strained) membrane (16.5 pairs, thickness=4μm, Ø=250μm, beam width=70μm, -length=125μm, radius of curvature R=2.4mm). The tuning speed is not affected as the thennal response (f_3dB~500Hz) is below the mechanical resonance frequency of the MEMS. The two-chip VCSEL assembly is mounted onto a SMA type connector. All measurements are perfonned at room temperature (20°C, Peltier-controlled) in continuous wave (cw) operation. The singlemode VCSEL emits output power up to P=0.9mW with high sidemode suppression (>30dB) even at threshold current of 3mA. More infonnation on the device structure, technology, and characteristics can be found elsewhere.

© 2007 IEEE