A highly efficient photodetector for squeezed light measurement in the gigahertz range

Appl. Phys. Lett. 127, 144001 (2025) · DOI: 10.1063/5.0290396

License: CC BY 4.0.

Abstract

Squeezed light plays a crucial role in state-of-the-art quantum metrology and quantum information experiments. There is significant interest in utilizing squeezed states at high MHz and GHz frequencies. However, past efforts to build suitable photodetectors at these frequencies have yet to yield the required high quantum efficiency. Here, we present the development of a high-frequency balanced photodetector with near-unity quantum efficiency, realized with off-the-shelf components. The detector operates in balanced mode up to approximately 500 MHz, above which the differential frequency response limits its performance. To obtain high sensitivity above 500 MHz, the detector can be efficiently used in an unbalanced homodyne detection scheme. We employ our detector in this unbalanced mode to measure a squeezing comb up to 6.4 GHz, achieving a squeezing level of up to 10.7 dB. By sharing our experience, specifically in identifying the unequal frequency response as a limiting factor, we aim to enable and advance further developments in the field.

Figures

10 panels with data across 4 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

• panel (c): Noise (dBm) against frequency (GHz) with 8 mW on each photodiode: the balanced shot noise (blue), the shot noise of photodiodes D1 (green) and D2 (orange), and the dark noise (yellow). data.csv

Fig. 2

• panel (a): Normalized squeezing comb with unbalanced homodyne detection on photodiode D1: noise relative to shot noise (dB) against frequency (GHz) for shot noise, dark-noise clearance, squeezing and anti-squeezing, dark noise subtracted, with zero-span points (circles). Gray lines mark the levels at the first FSR. The print's shading between shot noise and dark-noise clearance is not drawn. data.csv
• panel (b): Normalized squeezing comb with unbalanced homodyne detection on photodiode D2: noise relative to shot noise (dB) against frequency (GHz) for shot noise, dark-noise clearance, squeezing and anti-squeezing, dark noise subtracted, with zero-span points (circles). Gray lines mark the levels at the first FSR. The print's shading between shot noise and dark-noise clearance is not drawn. data.csv
• panel (c): Normalized squeezing comb with balanced homodyne detection: noise relative to shot noise (dB) against frequency (GHz) for shot noise, dark-noise clearance, squeezing and anti-squeezing, dark noise subtracted, with zero-span points (circles). Gray lines mark the levels at the first FSR. The print's shading between shot noise and dark-noise clearance is not drawn. data.csv

Fig. 3

• panel (a-1): Magnitude (dB) against frequency (GHz) of the transfer functions of photodiodes D1 and D2, with their shot-noise spectra (dark noise subtracted) for reference. The upper plot of printed panel (a); its phase plot is a-2. data.csv
• panel (a-2): Phase (degrees) of the transfer functions of photodiodes D1 and D2 against frequency (GHz), unwrapped so that it runs past 360 degrees. The lower plot of printed panel (a). data.csv
• panel (b): Measured (circles) and predicted (crosses) squeezing and anti-squeezing (dB) for balanced detection against frequency (GHz), at the comb teeth up to 3 GHz. data.csv

Fig. 4

• panel (a): DC output voltage (V) against optical power (mW) for photodiodes D1 and D2 (crosses), each with its linear fit. data.csv
• panel (b-1): Shot-noise spectra of photodiode D1, normalized noise (dB) against frequency (GHz), for nine optical powers from 0.1 to 10.0 mW and the dark noise. Traces are normalized to the 3.5 mW measurement (pink), dark noise subtracted; dashed lines are the expected shot-noise levels. The upper plot of printed panel (b). data.csv
• panel (b-2): Shot-noise spectra of photodiode D2, normalized noise (dB) against frequency (GHz), for nine optical powers from 0.1 to 10.0 mW and the dark noise. Traces are normalized to the 3.5 mW measurement (pink), dark noise subtracted; dashed lines are the expected shot-noise levels. The lower plot of printed panel (b). data.csv

Cite

Dennis Wilken, Jonas Junker, Michèle Heurs. A highly efficient photodetector for squeezed light measurement in the gigahertz range. Appl. Phys. Lett. 127, 144001 (2025). https://doi.org/10.1063/5.0290396

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