Pulsation of InGaAs Photodiodes in Liquid Helium for Driving Josephson Arrays in AC Voltage Realization

Abstract

A commercially available InGaAs p-in photodiode chip has been custom packaged and high-speed operated in liquid helium. The photodiode was driven by light pulses using a dc-biased 1310-nm laser, a Mach-Zehnder modulator, and a return-to-zero pulse pattern generator up to 15 GHz clock frequencies, which produced pulse widths down to 77 ps and maximum peak current heights above 10 mA. With the prospect of using this photodiode assembly to operate pulse-driven Josephson junction arrays for ac voltage realization, pulsation modes with constant pulse width and varying pulse density were applied to the diode, which resulted in consistent pulse shapes for bit rates as high as 7.5 Gb/s. This could yield realizable peak voltages as high as 15.525 µV per Josephson junction. Time-lapse pulse measurements were performed over the span of 90 min, which demonstrated good waveform stability. Using the measured current waveforms, the behavior of a typical Josephson junction was simulated according to the Stewart-McCumber model, which resulted in an operational margin of 2 mA for the first Shapiro step.

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

“…This could directly explain the limitations for higher sigma-delta code amplitudes. However, when investigated with a sampling oscilloscope, the full width at half maximum of the optical pulses was about 80 ps at 4 K [23], which matches electrical pulses that have been successfully used with this JAWS array.…”

“…Providing a relatively large lens diameter of 100 µm, it is easy to implement it to the setup for a robust and reliable operation. Detailed optimizations and investigations of the high-speed performance at room-temperature and 4 K were performed [21], [22] and the optical pulse setup is described [23]. Finally, the PD produces the electrical pulses, which are transferred over a comparable short distance of about 4 cm from the custom-made silicon-based PD-chip-carrier (PDCC) to the JAWS chip (see Fig.…”

“…We also note that for A ΣΔ > 0.3 the JAWS is not on quantized operation margins anymore and higher harmonics appear in the frequency spectrum. A detailed analysis of the optical generated pulses and comparison with the electrical pulses from the PPG in [23] was performed. It was discovered that the optical pulses show about 1.5 times larger rise/fall time compared to the electrical pulses at highest clock rates.…”

“…As part of a collaboration between Justervesenet, University of South-Eastern Norway (USN), NPL and PTB, the development of an optical drive for a JAWS system was also begun [18]- [23].…”

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.…”