Resonance fluorescence of single In(Ga)As quantum dots emitting in the telecom C-band

An emission wavelength around $1550 nm$ (telecom C-band) is highly appealing for nonclassical light sources, among others, due to the absorption minimum in standard glass fibers. In particular, semiconductor quantum dots at this wavelength promise to provide the outstanding results achieved with this emitter type in the near-infrared spectral region. Here, we study resonance fluorescence from InAs/GaAs quantum dots emitting in the telecom C-band under continuous wave and pulsed excitation. For the prior case, the quantum dot is excited in the strong driving regime and the characteristic Mollow triplet is observed allowing to draw conclusions on the nature and quantitative influence of different decoherence mechanisms on the emission. Furthermore, under pulsed excitation, highly pure single-photon emission (⁠$g(2)(0)=0.023 ± 0.019$⁠) is demonstrated and a measurement of the photon indistinguishability (⁠$VTPI=0.144 ± 0.015$⁠; full width at half maximum of the time window for post-selection of $(305 ± 33)ps$ with an associated maximally attainable value $VTPI,p=0.955$⁠) is presented. In the process of making the emission properties of telecom quantum dots comparable to their well-established counterparts emitting in the near-infrared spectral region, these results represent a benchmark and provide valuable information for future optimization of sample structures.