Photothermal resistivity alignment of optical fibers to SNSPD

TL;DR

This paper introduces a simple optoelectronic method for aligning optical fibers to SNSPDs by using the photothermal response of the nanowire, enabling high-precision, robust fiber-to-detector alignment.

Contribution

The authors present a novel fiber alignment technique leveraging temperature-dependent resistivity changes in SNSPDs caused by optical heating, offering improved accuracy and robustness over existing methods.

Findings

Achieved sub-micron alignment precision.

Method is insensitive to fiber angle and height variations.

Provides an alternative to back-reflection or transmission-based alignment.

Abstract

We demonstrate a straightforward optoelectronic fiber alignment technique for superconducting nanowire single-photon detectors (SNSPDs) that exploits the temperature-dependent resistance of the nanowire under optical absorption. The target nanowire is illuminated via the fiber, and the local absorption of light heats the wire, causing a change in its resistivity. Scanning the fiber over the nanowire, the change in its resistivity is monitored by lock-in amplifier, mapping the spatial photothermal response correlated to absorption and coupling efficiency. The maximum of the response corresponds to optimal fiber-SNSPD alignment. This method allows for aligning the fiber to the center of the meander with sub-micron precision. The response is robust to variations in the angle and height of the fiber, providing an alternative or complement to fiber-to-chip alignment methods based on the back-reflection or transmission measurement.