Electron beams can acquire designed phase modulations by passing through nanostructured material phase plates. These phase modulations enable electron wavefront shaping and benefit electron microscopy, spectroscopy, lithography, and interferometry. However, in the fabrication of electron phase plates, the typically used focused-ion-beam-milling method limits the fabrication throughput and hence the active area of the phase plates. Here, we fabricated large-area electron phase plates with electron-beam lithography and reactive-ion-etching. The phase plates are characterized by electron diffraction in transmission electron microscopes with various electron energies, as well as diffractive imaging in a scanning electron microscope. We found the phase plates could produce a null in the center of the bright-field based on coherent interference of diffractive beams. Our work adds capabilities to the fabrication of electron phase plates. The nullification of the direct beam and the tunable diffraction efficiency demonstrated here also paves the way towards novel dark-field electron-microscopy techniques.

A complete description of the work may be found here.

We demonstrate saturated internal detection efficiency at 1550 nm wavelengths for meander-shaped superconducting nanowire single-photon detectors made of 3 nm thick MoSi films with widths of 1 and 3 μm and active areas up to 400 × 400 μm². Despite hairpin turns and a large number of squares (up to 10⁴) in the device, the dark count rate was measured to be ∼10³ cps at 99% of the switching current. This value is about two orders of magnitude lower than the results reported recently for short MoSi devices with shunt resistors. We also found that 5 nm thick MoSi detectors with the same geometry were insensitive to single near-infrared photons, which may be associated with different levels of suppression of the superconducting order parameter. However, our results obtained on 3 nm thick MoSi devices are in good agreement with predictions in the frame of a kinetic-equation approach

A complete description of the work may be found here.

Our group participated to the CLEO2020 conference with four talks. You can find the recordings at the following links:

• Dr. Mina Bionta Towards Integrated Attosecond Time-Domain Spectroscopy (00:02:05) [also featured in the talk: What’s Next in Ultrafast Optics – Hot Topics at CLEO: 2020]

• Marco Colangelo Superconducting nanowire single-photon detector on thin-film lithium niobate photonic waveguide (01:30:48) [also featured in the talk: What’s Next in Integrated Photonics – Hot Topics at CLEO: 2020]

• Marco Turchetti Low-Energy Optical Pulse Detection Using Biased Plasmonic Nanoantenna (00:02:33)

• Dr. Di Zhu – highlighted talk (30 min) – Photon-Number Resolution Using Superconducting Tapered Nanowire Detector (00:59:41)

Time- and number-resolved photon detection is crucial for quantum information processing. Existing photon-number-resolving (PNR) detectors usually suffer from limited timing and dark-count performance or require complex fabrication and operation. Here, we demonstrate a PNR detector at telecommunication wavelengths based on a single superconducting nanowire with an integrated impedance-matching taper. The taper provides a kΩ load impedance to the nanowire, making the detector’s output amplitude sensitive to the number of photon-induced hotspots. The prototyping device was able to resolve up to four absorbed photons with 16.1 ps timing jitter and <2 c.p.s. device dark count rate. Its exceptional distinction between single- and two-photon responses is ideal for high-fidelity coincidence counting and allowed us to directly observe bunching of photon pairs from a single output port of a Hong-Ou-Mandel interferometer. This detector architecture may provide a practical solution to applications that require high timing resolution and few-photon discrimination.

A complete description of the work may be found here.