(a) Experimental setup. Two pulsed lasers in ASOPS pump-probe configuration are combined by an objective lens (0.55 NA) and focused into the transducer substrate interface where the probe beam is captured by a second objective (0.42 NA) and detected in a photodiode. The system is built around a microscope to enable complementary optical imaging. A fluorescence detection arrangement allows the state of a cell to be assessed. (b) Transducer and sample arrangement. The pump beam is absorbed while the probe beam is transmitted by the transducer (with dimensions Au = 20 nm, ITO = 140 nm and Au = 20 nm) to allow detection while protecting the cell from optical exposure. The substrate is sapphire to prevent temperature rise.