Laser diode stabilisation for coherent driving of rare earth ions

We report on the frequency stabilisation of an extended cavity diode laser for the coherent driving of thulium ions. This stabilisation loop uses a single locking point on an intra-cavity electro-optic crystal. It uses neither the diode current, nor any piezoelectric actuator, making its conception simple, versatile, and independent of the diode itself. Thanks to this, the laser linewidth with respect to the reference cavity is reduced well below 1 kHz. The laser coherence time is then much longer than the atomic coherence lifetime of the thulium ions. The performances of this stabilised source are used in basic coherent driving experiments in a Tm³⁺:YAG crystal. Efficient inversion of population by single adiabatic transfer and creation of narrow absorption lines by repetitive excitations are achieved.