Bare Cavity Mode Research Articles

Observation of a hybrid state of Tamm plasmons and microcavity exciton polaritons.

We present evidence for the existence of a hybrid state of Tamm plasmons and microcavity exciton polaritons in a II-VI material based microcavity sample covered with an Ag metal layer. The bare cavity mode shows a characteristic anticrossing with the Tamm-plasmon mode, when microreflectivity measurements are performed for different detunings between the Tamm plasmon and the cavity mode. When the Tamm-plasmon mode is in resonance with the cavity polariton four hybrid eigenstates are observed due to the coupling of the cavity-photon mode, the Tamm-plasmon mode, and the heavy- and light-hole excitons. If the bare Tamm-plasmon mode is tuned, these resonances will exhibit three anticrossings. Experimental results are in good agreement with calculations based on the transfer matrix method as well as on the coupled-oscillators model. The lowest hybrid eigenstate is observed to be red shifted by about 13 meV with respect to the lower cavity polariton state when the Tamm plasmon is resonantly coupled with the cavity polariton. This spectral shift which is caused by the metal layer can be used to create a trapping potential channel for the polaritons. Such channels can guide the polariton propagation similar to one-dimensional polariton wires.

Characterization of two-threshold behavior of the emission from a GaAs microcavity

We compare two regimes indicative of polariton lasing and photon lasing of a planar GaAs/GaAlAs microcavity with zero detuning between the bare cavity mode and the quantum-well exciton. In particular, we investigate the cavity emission subsequent to nonresonant pulsed excitation. For the ground state emission from the lower energy-momentum dispersion branch we find a two-threshold behavior in the input-output curve where each transition is accompanied by characteristic changes of the in-plane mode dispersion. We demonstrate that the thresholds are unambiguously evidenced in the photon statistics of the emission based on the second-order correlation function. Moreover, the distinct two-threshold behavior is confirmed in the evolution of the emission pulse duration. Our findings show that a comprehensive study of spectral and temporal characteristics of the emission from a semiconductor microcavity can be used to characterize the different emission regimes.

Dynamics of the transition from weak to strong exciton‐photon coupling regime in a GaAs microcavity: angle resolved measurements

AbstractThe emission dynamics of a GaAs microcavity with embedded quantum wells at different angles of observation with respect to the sample normal under conditions of nonresonant picosecond‐pulse excitation is studied. At considerably high excitation densities, above a certain threshold, a very intense, fast, and spectrally narrow (at small angles of observation) component in the PL dynamics appears at short times, with the spectral position corresponding to the bare cavity mode, indicating the onset of lasing in the weak coupling regime. At longer times lasing ceases and the transition from weak to strong coupling regime is observed, as it follows from the spectral positions of the peaks in time‐resolved spectra at different angles of observation.At moderate excitation densities, kinetic dependences of the spectral shift and width of the lower polariton emission line (these parameters are often used to distinguish between strong and weak coupling regimes) as a function of angle of observation (polariton energy) are analyzed. In particular, it is shown that the decay time of the spectral shift is almost independent of the polariton energy and could be used as the characteristic time of the transition from weak to strong coupling regime. On the other hand, the decay time of the emission line broadening strongly depends on the polariton energy, indicating that the linewidth kinetics is essentially determined by the cooling of the electron‐hole system. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Observation of strong coupling through transmission modification of a cavity-coupled photonic crystal waveguide

We investigate strong coupling between a single quantum dot (QD) and photonic crystal cavity through transmission modification of an evanescently coupled waveguide. Strong coupling is observed through modification of both the cavity scattering spectrum and waveguide transmission. We achieve an overall Q of 5800 and an exciton-photon coupling strength of 21 GHz for this integrated cavity-waveguide structure. The transmission contrast for the bare cavity mode is measured to be 24%. These results represent important progress towards integrated cavity quantum electrodynamics using a planar photonic architecture.

Bistability and self-oscillations effects in a polariton-laser semiconductor microcavity

We report an experimental observation of polaritonic optical bistability of the laser emission in a planar semiconductor microcavity with a 100°A GaAs single quantum well in the strong-coupling regime. The bistability curves show crossings that indicate a competition between a Kerr-like effect induced by the polariton population and thermal effects. Associated with the bistability, laser-like emission occurs at the bare cavity mode.

Bistability double-crossing curve effect in a polariton-laser semiconductor microcavity

Departamento de Fisica, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil(Dated: February 1, 2008)We report an experimental observation of polaritonic optical bistability of the laser emission ina planar semiconductor microcavity with a 100˚A GaAs single quantum well in the strong-couplingregime. The bistability curves show crossings that indicate a competition between a Kerr-like effectinduced by the polariton population and thermal effects. Associated with the bistability, laser-likeemission occurs at the bare cavity mode.

Optical bistability and laserlike emission in a semiconductor microcavity

We report the experimental observation of hysteresis in the optical response of a semiconductor microcavity under normal mode coupling regime. A third resonance mode, spectrally lying at the bare cavity mode frequency, suddenly appears in the reflectivity and resonant Rayleigh scattering spectra when increasing the excitation power, resulting in a coexistence of three resonance modes. Bistability loops in both microcavity optical response are found at the energy of this third mode. Associated to the bistability, laserlike emission occurs at the bare cavity mode.

Coexistence of low threshold lasing and strong coupling in microcavities

We report the coexistence of low threshold lasing and strong coupling in a high-quality semiconductor microcavity under near-resonant optical pumping. A sharp laser mode splits from the lower-polariton branch and approaches the bare cavity mode frequency as the pump power increases. The lasing is produced by low density localized exciton states, which are weakly coupled to the cavity mode. The appearance of this lasing mode distinguishes quantum-well excitons into those which are strongly or weakly coupled with the cavity mode.

Polariton Spin Dynamics in II-VI Microcavities

The spin dynamics of cavity polaritons, in the non-linear regime, present a novel and striking behaviour of the degree of polarization of photoluminescence. It reaches its maximum value at a finite time after excitation with a light pulse, and is strongly influenced by the exciton-cavity detuning. In the case of negative detuning, the relaxation towards K ∼ 0 states is governed by the polariton final state stimulated scattering, the emission is counter-polarized with the excitation and the polarization reaches very large negative values. In the case of positive detuning, the emission arises from the bare cavity mode, indicating a transition to the weak coupling regime; nevertheless, a very large positive polarization is observed. In addition to the large degrees of polarization of the emission, an energy splitting is observed between the two circularly polarized components of the photoluminescence, which is directly related to the anomalous behaviour of the polarization.

Numerical investigations of cavity mode instabilities induced by a Gaussian gain medium

The variational equations of Firth [W.J. Firth, Opt. Commun. 22 (1977) 226] are used to study instabilities of the Gaussian mode of a resonator containing a Gaussian gain medium. A series of symmetric two-mirror resonators were chosen for study. When the Rayleigh range of the bare cavity Gaussian mode becomes much greater than the cavity length, and the effective gain spot size drops below that of the bare cavity mode, regions of gain in which the cavity does not have a bound, stable modes appear. This is similar to the results obtained by Firth [W.J. Firth, Opt. Commun. 27 (1978) 267] with a confocal cavity. The results are compared to diffraction calculations for the one of the resonators. The comparison points out some intriguing areas of agreement, and suggest that it may be possible to observe the effects in a real system.

Laser emission from semiconductor microcavities: The role of cavity polaritons

We present an experimental study on the role of cavity polaritons in laser emissions from a GaAs quantum-well microcavity. We show that cavity polaritons play no role in the laser emission process when the cavity is nearly resonant with the excitons. The laser emissions emerge from the bare cavity mode instead of from a cavity-polariton branch and the threshold density is much higher than the saturation density at which cavity polaritons vanish. We also show that the presence of emission doublets near the lasing threshold, which was previously taken as an evidence for laser emission from cavity polaritons, is primarily the result of spatial and/or temporal variations of exciton densities within the excitation volume.