We present a faster repumping scheme for strontium magneto-optical traps operating on the broad
5s21S0−5s5p1P1 laser cooling transition. Contrary to existing repumping schemes, we directly address lost atoms that spontaneously decayed to the
5s4d1D2 state, sending them back into the laser cooling cycle by optical pumping on the
5s4d1D2−5s8p1P1 transition. We thus avoid the
∼100μs-slow decay path from
5s4d1D2 to the
5s5p3P1,2 states that is part of other repumping schemes. Using one low-cost external-cavity diode laser emitting at
448nm, we show our scheme increases the flux out of a 2D magneto-optical trap by
60% compared to without repumping. Furthermore, we perform spectroscopy on the
5s4d1D2−5s8p1P1 transition and measure its frequency
ν88Sr=(668917515.3±4.0±25)MHz. We also measure the frequency shifts between the four stable isotopes of strontium and infer the specific mass and field shift factors,
δνSMS88,86=−267(45)MHz and
δνFS88,86=2(42)MHz. Finally, we measure the hyperfine splitting of the
5s8p1P1 state in fermionic strontium, and deduce the magnetic dipole and electric quadrupole coupling coefficients
A=−4(5)MHz and
B=5(35)MHz. Our experimental demonstration shows that this simple and very fast scheme could improve the laser cooling and imaging performance of cold strontium atom devices, such as quantum computers based on strontium atoms in arrays of optical tweezers.