We describe an optical sensor using photonic quantum ring lasers and resonance-enhanced photodetectors for the purpose of counting object discrimination. Due to the angle-dependent peak wavelength shift characteristics of the photonic quantum ring laser, an emission at an angle of 0ϳ30 deg from a perpendicular direction was reflected and absorbed in the resonance-enhanced photodetector, with a peak responsivity of 0.107 A/W at 757 nm. The use of the photonic quantum ring laser at an optimized angle in this monolithically integrated system, based on a distributed Bragg partial reflector structure, can lead to a compact, low cost, dust-free optical sensor and counter.

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