Picosecond time resolved studies of nonradiative relaxation in ruby and alexandrite

Abstract

Dynamics of the nonradiative transitions between the 4T2 pump band and the 2E storage level of the trivalent chromium ion in ruby and alexandrite crystals is studied using the picosecond excite‐and‐probe absorption technique. A 527‐nm picosecond pulse excites the 4T2 state of the Cr3+ ion, and an infrared picosecond probe pulse monitors the subsequent growth and decay of population in the excited states as a function of pump‐probe delay. An upper limit of 7 ps is determined for the nonradiative lifetime of the 4T2 state in ruby. A vibrational relaxation time of 25 ps for the 4T2 band in alexandrite is estimated. The time to attain thermal equilibrium population between the 2E and 4T2 levels of alexandrite following excitation of the 4T2 band is estimated to be ∼100 ps.