A fully solution-processed organic microcavity laser in the strong light-matter coupling regime

Abstract

Solid-state semiconductor lasers underpin technologies from telecommunications and data storage to sensing, medical diagnostics, and emerging quantum communication. Polaritons-hybrid exciton-photon states have further extended this reach, enabling room-temperature quantum effects such as low-threshold lasing and single-photon nonlinearities. Organic semiconductors are ideal for polaritonics due to their large exciton binding energy, strong optical nonlinearities, and straightforward processing, making them attractive for both classical and quantum photonics. While solution-processed organic films have been widely explored, their optical cavities have almost always been fabricated using vacuum deposition, limiting the realization of truly scalable and low-cost devices. Here, we report the first organic laser microcavities fabricated entirely by solution processing, which operate in the strong coupling regimeThe resulting platform can be driven reliably to high excitation densities, where we observe a reversible, interaction-driven redistribution of the polariton condensate, revealing a distinct polariton lasing behaviour in organic microcavities. Together, the fabrication approach and the observed lasing dynamics establish a route toward scalable polaritonic and quantum photonic technologies and provide new opportunities for studying nonlinear polariton physics in organic systems.

Figures (19)

• Figure 1: (a) Schematic illustration and corresponding scanning electron microscopy image of the all-solution-processed microcavity composed of alternating Nafion and titanium hydroxide/poly(vinyl alcohol) hybrid films as distributed Bragg reflectors (DBRs), with a 260-nm-thick DPAVB:polystyrene film as the active layer. (b) Schematic of the spin-coating process used for DBR fabrication. Each DBR pair is deposited through the following steps: (1) spin coating of titanium hydroxide/poly(vinyl alcohol) solution, (2) annealing, (3) spin-coating of Nafion, and (4) annealing.
• Figure 2: (a) Reflectivity spectrum of the polariton microcavity at normal incidence (black line), overlaid with the absorption (blue shaded) and emission (green shaded) spectra of the active material. The red peak corresponds to the photoluminescence (PL) from the lower polariton band bottom. The black dashed box shows the DPAVB molecule while the blue dashed box highlights the ASE region
• Figure 3: (a) Power-dependent LP photoluminescence intensity (black dots) and linewidth (blue dots). $\Delta$ is the exciton-cavity detuning and Q is determined from five low-fluence measurements integrated over small collection angles. (b) Representative LP photoluminescence spectra recorded below and above the lasing threshold. (c–e) Angle-resolved LP emission below threshold (c) and above threshold (d, e). A sharp collapse of the emission into the bottom of the LP dispersion is observed at threshold (d), followed by a progressive blueshift and redistribution at higher excitation densities (e). The white dashed line in c-e) is a polynomial fit to the LP dispersion at 0.5 $P_{\mathrm{th}}$, showing that the condensate remains confined within the below-threshold LP branch. The left-hand side of panels (c–e) is plotted on a linear scale to highlight qualitative spectral evolution, while the right-hand side uses a logarithmic scale to visualize how well the condensate remains confined within the LP dispersion. (f, g) Michelson interferograms of the condensate at 1.1 $P_{\mathrm{th}}$ and 4.5 $P_{\mathrm{th}}$, respectively. (f) Just above threshold, clear interference fringes emerge, indicating the buildup of spatiotemporal coherence. (g) At higher excitation densities, the fringes extend over the entire excitation area but become less distinct.
• Figure 4: Real-space evolution of the polariton condensate. (a–c) Emission profiles under Gaussian pumping at different excitation powers: below threshold (a), just above threshold ($\sim$1.4$P_{\mathrm{th}}$, b), and at high power ($\sim$9.4$P_{\mathrm{th}}$, c). The condensate first forms at the pump center before redistributing outward into a reversible annular profile. (d) Power-dependent emission intensity extracted at increasing radial distances from the pump center. The central emission saturates at high fluence, while off-center regions brighten with progressively higher thresholds, consistent with repulsive polariton–reservoir and polariton-polariton interactions driving outward flow.
• Figure 5: Thermalization of the polariton condensate. (a–c) Real-space resolved emission spectra under Gaussian pumping at different excitation powers above threshold: a) $\sim$3.3$P_{\mathrm{th}}$, b) $\sim$5.3$P_{\mathrm{th}}$, and c) $\sim$13.1$P_{\mathrm{th}}$. (d-f) Fits of the thermal tail to the Maxwell-Boltzmann distribution, with the obtained fit temperatures indicated along with 95% confidence bounds. The solid black lines mark the data range included in the least-squares fitting. The data (red) are obtained by integrating over the spatial axis between the horizontal gray lines in (a-c), from -30µm to 30µm. Fit residuals are plotted in linear scale on the right‑hand y‑axis in the same (arbitrary) intensity units as the spectra. For root‑mean‑squared error (RMSE) and fit window sensitivity analysis, see Supplementary Fig. \ref{['S_fig:fit_analysis']}.