We document the lasing performance of a waveguiding layer of Ti:sapphire, of $\sim 12-\mathit{\mu }\mathrm{m}$ thickness, grown by pulsed laser deposition from a 0.12–wt. % Ti₂O₃ Ti:sapphire single-crystal target onto an undoped $z$-cut sapphire substrate. Lasing around 800 nm is observed when the waveguide layer is pumped by an argon-ion laser running on all-blue-green lines, with an absorbed power threshold of 0.56 W, with high-reflectivity $\left(R>98\%\right)$ mirrors. With a 5% pump duty cycle and a $T=35\%$ output coupler, a slope efficiency of 26% with respect to absorbed power is obtained, giving quasi-cw output powers in excess of 350 mW.