Investigation of hybrid microlens integration with vertical-cavity surface-emitting lasers for free-space optical...

In a novel one-step process, a vertical-cavity surface-emitting laser (VCSEL, operation wavelength of 980 nm) is integrated with a hybrid microdiffractive lens by focused ion beam milling (FIBM) for use in freespace optical links. A hybrid microlens with a diameter of 100 m, numerical aperture of 0.56, and sag height of 4.196 m, combined with a diffractive lens with continuous relief and 6 annuli, was designed and fabricated in one step by FIBM on the back of a VCSEL with a GaAs substrate for beam collimation. A previous VCSEL integrated with a pure diffractive lens had a half-divergence angle of 0.6 degrees ; the half-divergence angle of the VCSEL with the hybrid microlens was improved to 0.3 degrees . Test results show that athermalization with respect to the variation in operating temperature can be realized with the hybrid microlens.