Efficient fiber-coupled single-photon sources based on quantum dots

Date: 
Monday, February 26, 2018 - 4:00pm
Speaker: 
Raphael Daveau
Speaker's Institution: 
Niels Bohr Institute

Many photonic quantum information processing applications would benefit from a high brightness, fiber-coupled source of triggered single photons. Sources based on quantum dots coupled to nanophotonic waveguides are very promising candidates as they feature a near-unity emitter-waveguide coupling efficiency. The main challenge remains to implement an efficient way to transfer the photons off-chip to an optical fiber.

First, I will present a high-purity source of indistinguishable single photons where the efficient off-chip coupling is ensured by transferring the photons from a waveguide taper to a lensed fiber. Quasi-resonant and resonant excitation is performed on the quantum dots as a means to generate highly indistinguishable photons. A single-photon purity larger than 99.4 % and a photon indistinguishability of up to 94 ± 1% are measured by using p-shell excitation combined with spectral filtering.

In the second part of the talk, I will show that evanescent coupling from a tapered waveguide to a microfiber can be used as an alternative and more efficient way to directly transfer photons to a fiber.  A coupling efficiency from chip to fiber up to 80 % is demonstrated, thereby making a single-photon source with an efficiency on the order of 10-15 %. These two studies open a clear pathway towards the creation of an efficient fiber-coupled source of indistinguishable single photons.