Delayed formation of coherence in the emission dynamics of high-Q nanolasers

Abstract

In the realization of ultrasmall semiconductor lasers, cavity-QED effects are used to enhance spontaneous emission and enable the lasing threshold to be crossed with gain contributions from only a few solid-state emitters. Operation in this regime fosters correlation effects that leave their fingerprint especially in the emission dynamics of nanolasers. Using time-resolved photon-correlation spectroscopy, we show that in a quantum-dot photonic-crystal nanolaser emitting in the telecom band, second-order coherence associated with lasing is established on a different timescale than the emission itself. By combining measurements with a microscopic semiconductor laser theory, we attribute the origin to carrier-photon correlations that give rise to non-Markovian effects in the emission dynamics that are not captured by laser rate-equation theories. Our results have direct implications with respect to the modulation response, repetition rate, noise characteristics, and coherence properties of nanolasers for device applications.

Real time g(2) monitoring with 100 kHz sampling rate

“…Hereby only those field modes that overlap spectrally, spatially and temporally with the LO are amplified. From the recorded field quadratures, the second-order correlation function g (2) (0) may then be calculated by evaluating the statistical moments of a sufficient number of samples according to equations (5)(6)(7). The time resolution of this experiment is determined by three numbers: First, the temporal resolution ∆τ is given by the duration of one LO pulse, as during this time the signal photons are amplified.…”

“…An adequate measurement of the coherence properties of light requires an experimental setup with a temporal resolution at least comparable to the coherence time of the light field under investigation. Since the first demonstrations of photon bunching using two photomultipliers [4], detector technology has advanced significantly in terms of sensitivity and quantum efficiency [5][6][7]. Also, several experimental techniques have been developed in order to allow for studies of photon correlations at short timescales.…”

Time‐Resolved Second‐Order Coherence Characterization of Broadband Metallic Nanolasers

“…The leading edge of the pump pulse generates carriers in the higher QW or barrier states and these carriers rapidly relax into the lower QW states yielding spontaneous emission ( g 2 (0) > 1). [ 32 ] As the intensity of the pump pulse increases in time, population becomes sufficiently strong and the system is driven into the regime of coherent emission ( g 2 (0) = 1). [ 32 ] As nanolaser cavities have an ultrafast response, at the trailing edge of the pulse envelope (where the intensity of the pump pulse is low), SE dominates over coherent emission, leading to g 2 (0) > 1.…”

“…[ 32 ] As the intensity of the pump pulse increases in time, population becomes sufficiently strong and the system is driven into the regime of coherent emission ( g 2 (0) = 1). [ 32 ] As nanolaser cavities have an ultrafast response, at the trailing edge of the pulse envelope (where the intensity of the pump pulse is low), SE dominates over coherent emission, leading to g 2 (0) > 1. [ 32 ] Moreover, for higher excitation densities, stimulated emission is maintained for a longer time resulting in an asymmetry in the time‐resolved data (Figure 4b).…”

Thermal, Quantum Antibunching and Lasing Thresholds from Single Emitters to Macroscopic Devices

“…This model applies to atoms and ions with suitable energy level structure, and also to shallow quantum dots (possessing two localized levels) at temperatures low enough to neglect Coulomb and phonon interactions. Assuming that detuning and coupling coefficients with the mode are identical [7,16] is justified by numerical simulations for emitters with 10% random variations of detuning and coupling coefficients. In these simulations all emitters' variables -started from random initial conditions -after a transient converge to common values that match extremely well those obtained using the same parameters and expectation values for all emitters, see SM Fig.…”