I. Tin-vacancy electronic structure model A. Tin-vacancy Hamiltonian B. Microwave drive of spin qubit C. Microwave drive results D. Realizing a lambda scheme II. Characterization of tin-vacancy lambda scheme parameters III. Modelling all-optical coherent control A. Analytical model B. Master equation model C. Gate fidelities IV. Sample fabrication V. Equipment set-up A. Experimental details on primary optical system B. Experimental details on second optical system C. Measurement conditions for main-text data VI. Coherent population trapping model and simulations VII. Intensity-correlation measurement under resonant excitation VIII. Ramsey signal analysis A. Serrodyne frequency ω S B. Two-photon detuning δ C. Differential AC Stark effect ∆ AC D. Ramsey simulation IX. Spin lifetime T 1 measurement