A silicon photonic chip is provided. An active silicon layer that includes a photonic device is on a front side of the silicon photonic chip. A silicon substrate that includes an etched backside cavity is on a backside of the silicon photonic chip. A microlens is integrated into the etched backside cavity. A buried oxide layer is located between the active silicon layer and the silicon substrate. The buried oxide layer is an etch stop for the etched backside cavity.