We demonstrate room temperature heralded single photon generation in a CMOS-compatible silicon nanophotonic device. The strong modal confinement and slow group velocity provided by a coupled resonator optical waveguide produced a large four-wave-mixing nonlinearity coefficient gamma_eff =4100 W-1 m-1 at telecommunications wavelengths. Spontaneous four-wave-mixing using a degenerate pump beam at 1549.6 nm created photon pairs at 1529.5 nm and 1570.5 nm with a coincidence-to-accidental ratio exceeding 20. A photon correlation measurement of the signal (1529.5 nm) photons heralded by the detection of the idler (1570.5 nm) photons showed antibunching with g(2)(0)=0.19 +/- 0.03. The demonstration of a single photon source within a silicon platform holds promise for future integrated quantum photonic circuits

We present the design and characterization of a modern near-infrared photon counting module, able to exploit the best performance of InGaAs/InP single-photon avalanche diodes for the detection of fast and faint optical signals up to 1.7 μm. Such instrument is suitable for many applications, thanks to the user-friendly interface and the fully adjustable settings of all operating parameters. We extensively characterized both the electronics and the detector, and we validated such instrument up to 133 MHz gate repetition frequency, for photon-counting and photon-timing applications, with very clean temporal response and excellent timing performance of less than 100 ps.

Low noise single-photon sources are a critical element for quantum technologies. We present a heralded single-photon source with an extremely low level of residual background photons, by implementing low-jitter detectors and electronics and a fast custom-made pulse generator controlling an optical shutter (a LiNbO3 waveguide optical switch) on the output of the source.\ud This source has a second-order autocorrelation g(2)(0) = 0.005, and an output noise factor (defined as the ratio of the number of noise photons to total photons at the source output channel)\ud of 0.25(1)%. These are the best performance characteristics reported to date

We present a new compact system for time-domain diffuse optical spectroscopy of highly scattering media operating in the wavelength range from 1100 nm to 1700 nm. So far, this technique has been exploited mostly up to 1100 nm: we extended the spectral range by means of a pulsed supercontinuum light source at a high repetition rate, a prism to spectrally disperse the radiation, and a time-gated InGaAs/InP single-photon avalanche diode working up to 1700 nm. A time-correlated single-photon counting board was used as processing electronics. The system is characterized by linear behavior up to absorption values of about 3.4 cm(-1) where the relative error is 17%. A first measurement performed on lipids is presented: the absorption spectrum shows three major peaks at 1200 nm, 1400 nm, and 1700 nm.

We experimentally investigate the smallest germanium waveguide cavity resonators on silicon that can be designed to work around 1.55 µm wavelength and observe an almost 30-fold enhancement in the collected spontaneous emission per unit volume when compared to a continuous germanium film of the same thickness. The enhancement is due to an effective combination of (i) excitation enhancement at the pump wavelength, (ii) emission enhancement (Purcell effect) at the emission wavelength, and (iii) effective beaming by the nanoresonators, which act as optical antennas to enhance the radiation efficiency. Our results set a basis for the understanding and engineering of light emission based on subwavelength, CMOS-compatible nanostructures operating at telecommunication wavelengths.Over the last decade germanium has been proposed as one of the most promising materials for light detection, modulation, and emission in silicon-photonics architectures [1][2][3]. Its direct bandgap, which is only about 140 meV larger than the fundamental indirect band-gap [4], ensures excellent absorption and promising emission properties, which recently led to the realization of integrated photodetectors [5][6][7][8], electroluminescent devices [9,10], and to the demonstration of optically-pumped [11] and electrically-pumped [12] Ge lasers. An attractive feature of the Ge optical properties is the overlap between the direct emission band and the conventional telecommunication window around the 1.55 µm wavelength. Along the road towards integrated Ge light sources, significant efforts have been devoted to material engineering in terms of strain [13][14][15][16][17] and doping [18,19], in order to make radiative recombination more effective and create the conditions for population inversion and gain [20,21]. Also photonic engineering has been applied in order to establish cavity resonances at the desired emission wavelengths. Cavities based on photonic crystals have played a major role in this field, achieving large emission enhancement factors and high directionality [22][23][24]. A particularly appealing perspective, leading to compact and cost-effective solutions, is the direct shaping of the active Ge material as a cavity for photons, which allows one to spectrally purify, enhance, and re-direct photon emission. While this concept has been successfully applied to the development of waveguide [11,25], photonic-crystal [26], and disk resonators [27], the overall size of these photonic devices was generally much larger (from several µm to mm size) than the free-space operating wavelength λ 0 , although, in principle, the volume of a resonant dielectric cavity can be as small as about (λ 0 /2n) 3 , n being the refractive index of the dielectric. It is one of the main paradigms of nano-optics that size reduction of modal volumes can increase light-matter interaction and boost light emission, also possibly reducing the threshold for lasing. Moreover, the trend towards smaller light sources is clearly driven by the perspective integration of nano-d...