Unidirectional emission with ultra-small divergence angle in deformed pentagonal microcavities

Unidirectional emission, one of the key technologies to achieve large-scale photonic integration, plays an important role in optical antennas, high-performance grating couplers, and energy-efficient lasers. At the same time, high chirality has demonstrated its potential application in highly sensitive optical sensors and coherent light sources with miniaturized sizes. Here, we designed a deformed circular-sided pentagonal microresonator (CPM) with low refractive index material for the combination of unidirectional light emission and high chirality. Two typical materials of polymer and silica are studied. For the polymer CPM, unidirectional emission with a divergence angle as small as 3° is predicted by constructing a notch at the vertex, and the chirality is 0.831. For the silica CPM, a divergence angle for unidirectional emission down to 10° and chirality as high as 0.9623 is predicted by introducing a channeling waveguide. The far-field emission pattern and chirality change drastically upon the attachment of a nanoparticle, predicting an ideal platform for a low-cost, portable, and highly sensitive nanoparticle detector.