  We report on our initial attempt to characterize the intrinsic frequency
response of metal-clad nanolasers. The probed nanolaser is optically biased and
modulated, allowing the emitted signal to be detected using a high-speed
photodiode at each modulation frequency. Based on this technique, the prospect
of high-speed operation of nanolasers is evaluated by measuring the D-factor,
which is the ratio of the resonance frequency to the square root of its output
power (fR/P_out^2). Our measurements show that for nanolasers, this factor is
an order of magnitude greater than that of other state-of-the-art directly
modulated semiconductor lasers. The theoretical analysis, based on the rate
equation model and finite element method simulations of the cavity is in full
agreement with the measurement results.
