Optical Pulse-Drive for the Pulse-Driven AC Josephson Voltage Standard

Abstract

We developed an optical pulse-drive for the operation of the Josephson Arbitrary Waveform Synthesizer (JAWS) using a fast photodiode (PD) operated at 4 K, close to the JAWS chip. The optical pulses are transmitted to the PD by an easily removable optical fiber attached to it. A bare-lensed PD is mounted by flipchip technique to a custom-made silicon-carrier chip. This carrier chip is equipped with coplanar waveguides to transmit the electrical pulses from the PD to the JAWS chip mounted on a separate printed circtuit board (PCB). The main components of this optical setup are a laser source, a high-speed Mach-Zehnder modulator, and the modulator driver. The waveform pattern is supplied by a commercial pulse pattern generator providing up to 15 GHz electrical return-to-zero (RTZ)-pulses. Unipolar sinusoidal waveforms were synthesized. Using a JAWS array with 3000 junctions, an effective output voltage of 6.6 mV root mean square (RMS) at the maximum available clock-frequency of 15 GHz was achieved. Higher harmonics were suppressed by more than 90 dBc at laserbias operation margins of more than 1 mA. Index Terms-AC Josephson voltage standard, Josephson arbitrary waveform synthesizer, SNS Josephson junction, sigma-delta modulation, optical pulse-drive, flip-chip technology. I. INTRODUCTION A FTER many years since the first realization of a pulsedriven AC Josephson voltage standard [1], recent developments in increasing the effective output voltage to 1 V root mean square (RMS) or even more [2]-[5] show that the use of a pulse-driven Josephson voltage standard is an important approach for voltage metrology. This AC Josephson voltage standard is often called "Josephson Arbitrary Waveform Synthesizer" (JAWS) and it is already used in several NMIs for metrology applications [6]-[15]. For the application in JAWS, the Josephson junctions are operated by short current pulses to Manuscript

Josephson voltage standards as toolkit for precision metrological applications at PTB

“…The optical fiber transfers the light pulses to the high-speed (28 Gbit s −1 ) InGaAs PDs at 4 K. Using a one-channel optical pulse-drive, unipolar sine waves were synthesized with stable operation margins using a 3000 junctions JAWS array in a signal frequency range from 60 Hz up to 10 kHz. With clock frequencies up to 15 GHz 6.6 mV rms voltage were generated (Kieler et al 2019). Following to this, a two-channel optical pulse-drive setup for generation of bipolar waveforms was established at PTB (figure 8).…”

“…Many further papers on implementation techniques, measurement setups, investigations and waveform synthesis (Ireland et al 2017, 2019, Bardalen et al 2020, Karlsen et al 2020, Nissilä et al 2021, Brevik et al 2022 indicate that the optical drive is a very active field with high potential for applications.…”

Stacked Josephson Junction Arrays for the Pulse-Driven AC Josephson Voltage Standard

“…For example, the implementation of different types of on-chip power dividers was successfully realized already [6], [7]. Another approach of implementing an optical pulse-drive with on-chip photodiodes (operated at 4 K) showed already first promising results [8],…”

Bipolar photodiode module operated at 4 K

“…In the EMPIR projects Q-WAVE and QuADC, the use of cryogenically operated PDs were demonstrated [5][6][7][8][9]. In these projects, InGaAs PDs were flip-chip bonded to silicon substrates and optical fibers were connected by use of epoxy bonded glass alignment sleeves.…”