Figure 4.

Observation of Purcell enhancement for GaSe thin film emission in a tunable microcavity. (a) PL traces under excitation with a pulsed laser at 415 nm, measured at T = 4.2 K using a streak-camera (spectral resolution of 0.2 nm). The traces are obtained by integrating the PL signal centered at 613 nm within the bandwidth of ≈2 nm in the spectrum measured by the streak-camera. The red curve shows the full-cavity PL decay, for which a lifetime of 70 ps is found. The blue trace shows PL decay with a lifetime of 700 ps in a film in the half-cavity configuration. (b) Photoluminescence power dependence for a GaSe film in a microcavity. PL measurements were performed at T = 4.2 K by varying the excitation power of a continuous-wave 532 nm laser. At high laser powers, a clear saturation of the GaSe film PL is observed (blue squares) when measured without the top concave mirror. In the full cavity, the cavity mode PL (red squares), fed by the GaSe film emission, shows no saturation. In the graph, the excitation power of the cavity mode is corrected by the measured transmission through the top mirror.