Increasing the reliability of DFB lasers on glass: the approach of encapsulation by wafer bonding

Erbium-doped integrated DFB lasers on glass exhibit a thermal stability and a very narrow linewidth that has been proven useful for many applications ranging from DWDM and Optomicrowave transmissions to airborne LIDAR. If the technologies used for the Erbium-doped active waveguides can differ (alumina, phosphate and silicate glasses have been reported among others), the laser cavity is always obtained thanks to a long Bragg grating implemented on the chip surface. Realizing cm-long submicrometric structure is a challenge that has been successfully overcome, but having such fragile features exposed on the top of a device entails several problems of packaging when reliability is concerned. Until now, this key issue has been addressed by depositing a conformal thin-film on the device surface, which is a complicated task since the deposited layer should be conformal, match the proper refractive index and respect the thermal budget of the process flow. In this paper, we present a different approach for the realization of Er-doped DFB lasers on glass where the grating-based cavity is implemented on a passive wafer that is then flip-chipped and wafer bonded on an Erbiumdoped phosphate glass containing active ion-exchanged waveguides. First results proved that a stable emission at a wavelength of 1.55 μm has been achieved for a fiber-coupled output power of more than 1mW.