Polariton laser using single micropillar GaAs-GaAlAs semiconductor cavities (0710.2060v3)

Abstract: Polariton lasing is demonstrated on the zero dimensional states of single GaAs/GaAlAs micropillar cavities. Under non resonant excitation, the measured polariton ground state occupancy is found to be as large as $10^{4}$. Changing the spatial excitation conditions, competition between several polariton lasing modes is observed, ruling out Bose-Einstein condensation. When the polariton state occupancy increases, the emission blueshift is the signature of self-interaction within the half-light half-matter polariton lasing mode.

• The paper demonstrates polariton lasing with ground state occupancy reaching up to 10^4 in 0D micropillar cavities under non-resonant excitation.
• It distinguishes polariton lasing from Bose-Einstein condensation by revealing a sharp threshold and spectral blueshift driven by polariton self-interaction.
• The study combines experimental and theoretical analyses to explore efficient polariton scattering in confined GaAs/GaAlAs structures, paving the way for novel coherent light sources.

Overview of Polariton Lasing in GaAs/GaAlAs Micropillar Cavities

The research paper titled "Polariton laser using single micropillar GaAs-GaAlAs semiconductor cavities" by Daniele Bajoni et al. presents a detailed paper on polariton lasing within micropillar cavities fabricated from GaAs/GaAlAs materials. The paper focuses on the properties and dynamics of polariton states under non-resonant excitation and provides insights into the distinction between polariton lasing and Bose-Einstein condensation.

Polariton Lasing in Micropillar Cavities

The authors demonstrate polariton lasing observed within zero-dimensional (0D) states of single GaAs/GaAlAs micropillar cavities. Under non-resonant excitation, they report a significant ground state occupancy of polaritons that reaches up to $10^4$. This state is characterized by a distinct threshold behavior, with a corresponding strong increase in emission intensity, emphasizing a macroscopic occupation of a single quantum state.

Theoretical and Experimental Foundation

The paper is anchored on the interesting properties of massive bosons. While Bose-Einstein condensation is associated with the accumulation of bosons in a single state at thermal equilibrium below a critical temperature, polariton lasing involves stimulated scattering towards the polariton ground state, driven by high occupancy.

The paper explains that in GaAs/GaAlAs micropillar cavities, optical modes are well defined due to the confinement in all spatial directions. This confinement results in a discrete and discernable energy spectrum, which removes wave-vector conservation constraints found in two-dimensional cavities. As a result, the scattering of polaritons in these micropillar cavities is notably efficient, facilitating the observation of polariton lasing.

Numerical Results and Observations

Significant numerical observations include:

• A transition from strong to weak coupling regimes at higher excitation powers, where conventional photon lasing overlaps with polariton lasing but under different conditions.
• Spectral blueshift associated with polariton lasing is attributed to self-interaction among polaritons within highly occupied states.
• In experiments, the emission spectra highlight a significant boost in integrated intensity, showcasing lasing behavior not consistent with a thermodynamic phase, hence ruling out Bose-Einstein condensation.

Practical and Theoretical Implications

This paper presents implications both theoretically and practically. Theoretically, it gives insight into the polariton self-interaction mechanisms and the unique behavior of 0D systems. On the practical side, these findings suggest potential advancements toward developing novel coherent light sources such as an electrically pumped polariton laser. Such systems might leverage the low effective mass of polaritons to achieve high-temperature lasing, which can be critical for integrated photonic applications.

Future Developments in AI and Quantum Technologies

The paper signifies promising future directions, particularly in realizing solid-state matter-wave lasers that can complement and enrich the capabilities of existing laser technologies. Furthermore, polariton-based systems could play a transformative role in enhancing quantum computing and communication technologies, given their unique interaction dynamics and the potential for achieving high coherence states at relatively higher temperatures.

In conclusion, the rigorous exploration of polariton dynamics in microstructured cavities by Bajoni et al. not only elucidates the fundamental aspects of polariton lasing but also heralds new opportunities for advanced photonic devices and systems within the AI and quantum technology landscape.