Abstract
Efficient and fast on-demand single photon sources have been sought after as critical components of quantum information science. We report an efficient and tunable single photon source based on an InAs quantum dot (QD) embedded in a photonic crystal cavity coupled with a highly curved μ-fibre. Exploiting evanescent coupling between the μ-fibre and the cavity, a high collection efficiency of 23% and Purcell-enhanced spontaneous emissions are observed. In our scheme, the spectral position of a resonance can be tuned by as much as 1.5 nm by adjusting the contact position of the μ-fibre, which increases the spectral coupling probability between the QD and the cavity mode. Taking advantage of the high photon count rate and the tunability, the collection efficiencies and the decay rates are systematically investigated as a function of the QD–cavity detuning.
Highlights
By changing the fibre contact position, originated from an effective refractive index change[28]
Where Q and V are the quality factor and the mode volume of the cavity mode, respectively; ε 0n2 is the dielectric permittivity for the cavity photon; ω and ω c are the frequencies of an emitter and the cavity, respectively; and Γ c is the linewidth of the cavity mode. μ eff is an effective dipole moment coupled with a cavity mode, which is defined by μeff
From the numerical simulations (Fig. 1d), we found that the resonant wavelength of a cavity mode is tunable by moving the contact position of the μ -fibre
Summary
A μ -fibre-coupled SPS based on a PhC cavity with an embedded QD is demonstrated. From the measured SP count rate of 300 kHz, total fibre collection efficiency ξ is estimated to be 23%; it remains over 5% until the cavity mode is detuned by 8 times the cavity linewidth. On-resonant QD lifetime is measured to be 200 ps, which shows strong Purcell enhancement compared to the QD lifetime in bulk GaAs. By changing the μ -fibre contact position, the detuning dependence of the decay rate is investigated. Since the QD is not located at the energy maximum of the cavity mode, both the SE factor and Purcell factor are degraded compared to the calculation. The curved μ -fibre-coupled PhC cavity system has strong points. It shows an efficient collection of single photons with a Purcell-enhanced SE rate. The total collection efficiency of 23% directly into the single mode fibre compares well with other efficient SPSs8,10,49
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