News

New Paper: “Free space-coupled superconducting nanowire single photon detectors for infrared optical communications”

This paper describes the construction of a cryostat and an optical system with a free-space coupling efficiency of 56.5% +/- 3.4% to a superconducting nanowire single-photon detector (SNSPD) for infrared quantum communication and spectrum analysis. A 1K pot decreases the base temperature to T = 1.7 K from the 2.9 K reached by the cold head cooled by a pulse-tube cryocooler. The minimum spot size coupled to the detector chip was 6.6 +/- 0.11 μm starting from a fiber source at wavelength λ = 1.55 μm. We demonstrated efficient photon counting on a detector with an 8 x 7.3 μm^2 area. We measured a dark count rate of 95 +/- 3.35 kcps and a system detection efficiency of 1.64% +/- 0.13%. We explain the key steps that are required to further improve the coupling efficiency.

Francesco Bellei, Alyssa P. Cartwright, Adam N. McCaughan, Andrew E. Dane, Faraz Najafi, Quinyuan Zhao, and Karl K. Berggren. Free space-coupled superconducting nanowire single photon detectors for infrared optical communications. ArXiv151105786 Phys. (2015). at <http://arxiv.org/abs/1511.05786>

New Book Chapter: “Self-assembly of block copolymers by graphoepitaxy”

We have written a book chapter about the self-assembly of block copolymers by graphoepitaxy. In the fabrication of a desired block copolymer (BCP) nanostructure for a particular application, a key challenge is the control of the BCP microdomain assembly. Graphoepitaxy is a solution for this challenge. Graphoepitaxy provides multifaceted mechanisms to order and directing microdomains and to fabricate complicated single-layer or multilayer structures over large areas. Topographical templates can be fabricated using different top-down lithography or self-forming methods. These templates direct the self-assembly through key mechanisms such as commensurability, lateral ordering, and confinement effect. Hence, many different morphologies, either equilibrium or nonequilibrium, can be controlled to produce desired nanopatterns. To date, BCP graphoepitaxy has been employed in many applications, from nanoelectronics to medical filters and memory storage to biological substrates.

The book chapter by S. M. Nicaise, A. Tavakkoli K. G. and K. K. Berggren, “Self-assembly of block copolymers by graphoepitaxy”, In: Directed self assembly of block co-polymers for nano-manufacturing, R. Gronheid and P. Nealey, Woodhead Publishing, 197-230 (2015).

Microsystems Technology Laboratory (MTL) annual report is published

A showcase of MTL’s diverse and creative research, this report contains 147 abstracts submitted by 40 research groups. The QNN group’s contributions can be found here:

Driving Stage for SFQ Circuits using a Single Nanocryotron

Modeling Superconducting Nanowire Circuits

Free-Space Coupled Superconducting Nanowire Single-Photon Detectors for Mid-IR Optical Communications

Measuring the Timing Jitter of WSi SNSPDs with Integrated nTron Readout

Templated Self-Assembly of Block Copolymer Thin Films Under Lithographic Confinement

Lithographic Control of Surface and Volume Plasmons in Aluminum

Interaction-Free Measurement by Three-Crystal Electron Interferometer

Membrane Nano-Gratings for Electron Diffraction