Fig. 4

Response of the virus laser to ligand-binding. a Spectra of V2 before (cyan) the addition of cp-mAb at 1.3 × 10¹⁶ photons pulse⁻¹ and after (light green) the addition of the antibody at 1.4 × 10¹⁶ photons pulse⁻¹. Each scatter point is the mean of four measurements at each wavelength and the curves are fits to the sum of two Voigt peak functions (dark blue) and a Lorentzian peak function (green). b Threshold behaviour of V2 before and after the addition of cp-mAb, same colours as (a). Lines represent individual fits of the data to equation (26). c Time-dependence of the intensity at 523.5 nm at pump energies initially above threshold at 1.3 × 10¹⁶ photons pulse⁻¹ ± 4.7% (purple) and below threshold at 1.6 × 10¹⁵ photons pulse⁻¹ ± 4.4% (green). The concentration of cp-mAb, which is a ligand bound by M13, in the gain medium after mixing increases in steps from 0 fmol mL⁻¹ to 9 fmol mL⁻¹, 29 fmol mL⁻¹ and then 90 fmol mL⁻¹. The arrows indicate when cp-mAb was added to the reservoir, and the lengths of the arrows are proportional to the amount added to the reservoir at each step. The squares and error bars represent the mean and standard deviation, respectively, of 7 measurements taken at each point in the time series. The variation in intensity at each time point is caused by small fluctuations in the pump energy and random variations in the response of the intensity to pumping. See Supplementary Figs. 7, 8 and 9 for all of the collected data. Source data are provided as a Source Data file