Compact Plasmonic Distributed-Feedback Lasers as Dark Sources of Surface Plasmon Polaritons

Plasmonic modes in optical cavities can be amplified through stimulated emission. Using this effect, plasmonic lasers potentially provide chip-integrated sources of coherent surface plasmon polaritons (SPPs). However, while have been experimentally demonstrated, they not generated propagating plasmons as their primary output signal. Instead, typically involve significant emission free-space photons that are intentionally outcoupled from the cavity by Bragg diffraction or leak reflector edges due to uncontrolled scattering. Here, we report a simple design allows for straightforward extraction lasing mode SPPs minimizing photon leakage. We achieve 10-μm-long distributed-feedback consisting Ag periodically patterned with ridges coated thin layer colloidal semiconductor nanoplatelets gain material. The designed second-order feedback direct experimental examination lasing-mode profile real- and momentum-space, good agreement coupled-wave theory. In contrast, demonstrate first-order-feedback remain dark above threshold signal leaves SPPs, highlighting potential such on-chip plasmons.