High power and ultra-low noise VECSEL for high dynamic range and wideband microwave optical links

We describe a compact, ultra-low noise and high-power laser implemented in a wideband externally-modulated optical link. The laser is based on a Vertical External Cavity Surface Emitting Laser designed for free-relaxation-oscillations operation, i.e. in the so-called class-A regime. Thanks to a specific design of the 1/2-VCSEL, a metamorphic Bragg mirror and a report on a copper substrate, an optical power of 110 mW is obtained at 1.55μm in the single frequency regime. The Class-A VECSEL exhibits a relative intensity noise below -170 dB/Hz over a wide frequency bandwidth, from 300 MHz to 40 GHz, except at the laser free spectral range (20.4 GHz). A VECSEL-based optical link and a low RIN Class-B DFB-laser-based optical link are implemented and compared in terms of gain and noise factor. Thanks to its flat and ultra-low noise over a wide frequency bandwidth, the VECSEL outperforms the DFB laser, in particular for frequencies larger than 30 GHz.