Waveguide-integrated niobium- nitride detectors for on-chip quantum nanophotonics.

NbN-based detectors can detect light from the granular regime (single or few photons) up to weak continuous photon fluxes at wavelengths ranging from visible light up to mid-IR. The article reports our recent results on a novel linear detector, the waveguide-integrated hot electron bolometer (HEB) capable to measure photon fluxes of large coherent beams in a regime in which superconducting nanowire single photon detectors (SNSPDs) are not efficient due to their strong nonlinearity. SNSPDs, photon number resolving detectors and amplitude multiplexing readout schemes, all integrated on photonic circuits are also discussed in the paper.

Photon-counting and analog operation of a 24-pixel photon number resolving detector based on superconducting nanowires.

We investigate the transition from the photon-counting to the linear operation mode in a large-dynamic range photon-number-resolving-detector (PNRD). A 24-pixel photon-number-resolving-detector, based on superconducting nanowires in a series configuration, has been fabricated and characterized. The voltage pulses, generated by the pixels, are summed up into a single readout pulse whose height is proportional to the detected photon number.

Superconducting series nanowire detector counting up to twelve photons.

We demonstrate a superconducting photon-number-resolving detector capable of resolving up to twelve photons at telecommunication wavelengths. It is based on a series array of twelve superconducting NbN nanowire elements, each connected in parallel with an integrated resistor. The photon-induced voltage signals from the twelve elements are summed up into a single readout pulse with a height proportional to the detected photon number.

Integrated autocorrelator based on superconducting nanowires.

We demonstrate an integrated autocorrelator based on two superconducting single-photon detectors patterned on top of a GaAs ridge waveguide. This device enables the on-chip measurement of the second-order intensity correlation function g(2)(τ). A polarization-independent device quantum efficiency in the 1% range is reported, with a timing jitter of 88 ps at 1300 nm.

Ultrasensitive N-photon interferometric autocorrelator.

We demonstrate a novel method to measure Nth-order (N=1,2,3,4) interferometric autocorrelation with high sensitivity and temporal resolution. It is based on the combination of linear absorption and nonlinear detection in a superconducting nanodetector, providing much higher efficiency than methods based on all-optical nonlinearities. Its temporal resolution is only limited by the quasiparticle energy relaxation time, which is directly measured to be in the 20 ps range for the NbN films used in this work.

Nanoscale optical detector with single-photon and multiphoton sensitivity.

We present the first nanoscale (down to approximately 50 x 50 nm(2)) detector displaying single-photon sensitivity and a nanosecond response. This type of nanodetector can also be operated in multiphoton mode, where the detection threshold can be set at N = 1, 2, 3, or 4 photons, thus allowing the mapping of photon number statistics on the nanoscale. Its operation principle based on that of hot-spot formation in superconducting nanowires allies the temporal resolution and sensitivity of superconducting single-photon detectors with subwavelength resolution and photon number discrimination.