In certain embodiments, a system for controlling a position of a focal point of a laser beam comprises a beam expander, a scanner, an objective lens, and a computer. The beam expander controls the focal point of the laser beam and includes a mirror and expander optical devices. The mirror has a surface curvature that can be adjusted to control a z-position of the focal point. The expander optical devices direct the laser beam towards the mirror and receive the laser beam reflected from the mirror. The scanner receives the laser beam from the beam expander and manipulates the laser beam to control an xy-position of the focal point. The objective lens receives the laser beam from the scanner and directs the beam towards the target. The computer receives a depth instruction, and sets actuation parameters to control the surface curvature of the mirror according to the depth instruction.
