Extended Data Fig. 10: Comparison of operational stability of lasers based on type-(I+II) QDs and rhodamine 6G dye.

Comparison of laser output intensity as a function of time for a solution of type-(I+II) QDs (r = 2.6 nm, l = 1.7 nm, h = 2.2 nm, and d = 0.3 nm) (blue circles) and rhodamine 6G dye (pale red and red squares). In both cases, the gain medium was excited by 532 nm, 5 ns, 10 Hz second harmonic pulses of a Nd:YAG laser. The QDs were dispersed in toluene, and rhodamine 6G was dissolved in a mixture of methanol and ethylene glycol (5:95 %, v/v). During the measurements, both solutions were in ‘static form’, that is, they were not stirred, flowed or otherwise agitated. During the stability test, the type-(I+II) QDs were excited using a per-pulse fluence of approximately 50 mJ cm⁻². The rhodamine 6G dye was excited using a per-pulse fluence of 15 mJ cm⁻² (pale red) and 50 mJ cm⁻² (red); the former intensity corresponded to excitation near the lasing threshold (14 mJ cm⁻²). The dye laser output intensity decreased continuously during the test. The initial rapid decay could be fitted to an exponential relaxation with a time constant of 30 min.