Intraband hole burning of colloidal quantum dots

CdSe, InP, and ZnO colloidal quantum dots of 1.5-2.5 nm radius show <3 meV homogeneous width at 10 K for the midinfrared 1 S-e- 1 P-e intraband transition around 300 meV. A weak temperature dependence leads to a homogeneous width of less than 10 meV at 200 K for 2.3 nm radius CdSe. The strength of the LO-phonon replica is in quantitative agreement with expectations from bulk parameters.