Spectral hole burning in the trivalent thulium ion

Spectral hole burning is reported for the trivalent thulium ion with measurements on the (3)H(6)(1) ? (3)H(4)(1) transition of LaF(3):Tm(3+) and two sites (A and B) of CaF(2):Tm(3+) at 1.5 K. Hole burning occurs by population storage in the metastable (3)F(4) level. The holes were scanned by an electric-field ramp applied directly to the sample, the frequency being calibrated by burning multiple holes with a frequency-modulated laser. This yielded the hole widths as well as the Stark coefficients for the transition studied, which are 8.3 kHz/V cm(-1) parallel to the C(2) axis (LaF(3):Tm(3+)) and for CaF(2):Tm(3+) are 25 kHz/V cm(-1) (site A), and 4.6 kHz/V cm(-1) (site B) for fields along the (001) direction. From the polarization behavior of the holes, the sites in CaF(2) are assigned to the F(-)-compensated C(4nu) and C(3nu) sites, respectively.