Transient hole-burning with a diode laser: a study of bacteriochlorophyll-a in a glass on a microsecond time scale

Abstract

We demonstrate transient hole-burning (THB) on a time scale of a few microseconds with a temperature- and current-controlled diode laser. The S1 ← S0 0-0 transition (Qy) of bacteriochlorophyll-a (BChl-a) in the glass triethylamine (TEA) was studied at λ = 780 nm, between 1.2 and 4.2 K. The burning mechanism of the transient holes is population storage in the triplet state. The decay time of the holes, of about 140 μs, is determined by the triplet-state lifetime of BChl-a. The transient holes were found to broaden by less than 10% when probed as a function of delay between 15 and 600 μs. They have the same width within experimental error (< 10%) as permanent holes detected a few minutes after being burnt. The results show that in the glass TEA there is no significant spectral diffusion in a time span of 7 orders of magnitude, i.e. between 15 μs and a few minutes. From a comparison of burning fluences used to obtain permanent and transient holes of the same depth, the efficiency of permanent hole-burning at T = 4.2 K was determined for this sample to be about 10−4.