arXiv subjects

Jaani Nissilä

Publications and source records attributed to Jaani Nissilä.

3 recordsLinked to original sources

arXiv2025

In-situ electro-optic sampling of microwave signals under cryogenic conditions and for superconducting applications

We demonstrate a cryogenic electro-optic sampling (EOS) setup that allows for the measurement of microwave signals at arbitrary positions on a cryogenic chip-scale device. We use a Josephson Arbitrary Waveform Synthesizer (JAWS) to generate quantum-accurate voltage signals and measure them with the EOS setup, allowing for the calibration of its response, yielding traceability of the microwave measurements to a quantum standard. We use the EOS setup to determine the time-domain response of ultrafast cryogenic photodiodes and the electrical reflection coefficient, i.e., the S11 scattering parameter, in a superconducting transmission line. Finally, we introduce an optical femtosecond pulse source which can be used to study the fidelity of superconducting transmission lines and terminations, as well as reflections from elements like Josephson junction arrays imbedded in them.

physics.optics↗

arXiv2023

Cryogenic fiber-coupled electro-optic characterization platform for high-speed photodiodes

We have developed a cryogenic characterization platform for ultrafast photodiodes, whose time domain responses are extracted by electro-optic sampling using femtosecond laser pulses in a pump-probe configuration. The excitation of the photodiodes with the pump beam and the electro-optic sampling crystals with the probe beam are realized in a fully fiber-coupled manner. This allows us to place the characterization platform in almost any temperature environment. As application example, we characterize the time-domain response of commercial p-i-n photodiodes with a nominal bandwidth of 20 GHz and 60 GHz at temperatures of 4 K and 300 K and in a large parameter range of photocurrent and reverse bias. For these photodiodes, we detect frequency components up to approximately 250 GHz, while the theoretical bandwidth of our sampling method exceeds 1 THz. Our measurements demonstrate a significant excitation power and temperature dependence of the photodiodes' ultrafast time responses, reflecting, most likely, changes in carrier mobilities and electric field screening. Since our system is an ideal tool to characterize and optimize the response of fast photodiodes at cryogenic temperatures, it has direct impact on applications in superconducting quantum technology such as the enhancement of optical links to superconducting qubits and quantum-accurate waveform generators.

physics.optics↗

arXiv2023

Supporting quantum technologies with an ultra-low loss silicon photonics platform

Photonic integrated circuits (PICs) are expected to play a significant role in the ongoing second quantum revolution, thanks to their stability and scalability. Still, major upgrades are needed for available PIC platforms to meet the demanding requirements of quantum devices. In this paper, we present a review of our recent progress in upgrading an unconventional silicon photonics platform towards such goal, including ultra-low propagation losses, low fibre coupling losses, integration of superconducting elements, Faraday rotators, fast and efficient detectors, as well as phase modulators with low loss and/or low energy consumption. We show the relevance of our developments and of our vision in two main applications: quantum key distribution - to achieve significantly higher key rates and large-scale deployment - and cryogenic quantum computers - to replace electrical connections to the cryostat with optical fibres.

physics.optics↗