All-glass miniature GHz repetition rate femtosecond laser cavity

Free-space optics allows for design freedom and control, but miniaturization and manufacturability are limited. Here, we present a method for manufacturing complex miniaturized free-space optical systems that combines contactless femtosecond laser-activated alignment with femtosecond laser 3D manufacturing of a substrate incorporating optomechanical elements. Specifically, we demonstrate a palm-sized, all-glass GHz femtosecond laser cavity, whose alignment and lasing operation are permanently tuned in a contactless manner via laser–matter interaction using another femtosecond laser. The manufactured Yb:KYW oscillator shows self-starting mode-locking with a diffraction-limited beam and outputs a stable train of solitons with 182 fs pulse width at 1.0925 GHz repetition rate, for 725 mW incident pump power.