Rovibrational optical cooling performed by broadband multimode diode laser in a Rb₂ supersonic beam

In this work, we have investigate optical rovibrational cooling of Rb₂ molecules in a thermal supersonic beam. Broadband multimode diode lasers were spectrally shaped using a 4F grating configuration, in order to performed optical transitions from X¹Σ_g⁺ ground state to the B¹Π_u excited potential in the 680-700 nm range. The optical shaping system is composed of a high efficiency transmission grating, a cylindrical lens and a digital micromirror device (DMD), which presents a theoretical resolution of 0.6 cm^-1. The molecules were detected by photoionization technique, through transitions from the X¹∑_g⁺ → B¹Π_u using a pulsed dye laser at 682 nm, and then photoionized by a 532 nm pulsed laser 5 ns later. The results indicate that we are able to pump most of the molecules to v_X=0, J_X≤10 using an appropriated optical shaping. Spectroscopy of the 2¹Σ_u⁺ was also performed in the 480 nm range, using this cold rovibrational sample. Simulations indicate that the optical pumping results should be improved by applying a virtually imaged phased array system.