All-optical production of ⁷Li Bose-Einstein condensation using Feshbach resonances

We show an all-optical method of making ⁷Li condensates using the tunability of the scattering length in the proximity of a Feshbach resonance. We report the observation of two Feshbach resonances on the |F=1,m_F=0⟩ state. A narrow (broad) resonance of 7 G (34 G) width is detected at 831±4 G (884₋₁₃⁺⁴ G). The position of the scattering length zero crossing between the resonances is found at 836±4 G. The broad resonance is shown to be favorable for runaway evaporation which we perform in a crossed-beam optical-dipole trap. Starting directly from the phase-space density of a magneto-optical trap we observe a Bose-Einstein condensation threshold in less than 3 s of forced evaporation.