Single-photon Hong-Ou-Mandel interference measures microcomb soliton pulse duration without amplification
Researchers measured femtosecond Kerr soliton pulses in microresonators via fourth-order quantum interference, without amplification or dispersion compensation, in a laboratory demonstration.
A study in Science Advances demonstrates a way to measure the temporal structure of dissipative Kerr solitons in optical microresonators using Hong-Ou-Mandel quantum interference. Such solitons underpin chip-scale frequency combs, with applications from coherent telecommunications to precision spectroscopy. science.org
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Conventional ultrafast diagnostics handle these pulses poorly. Their low energy and broad spectral bandwidth require optical amplification and careful dispersion compensation, which, according to the authors, can substantially distort the waveform.
In the new scheme, the soliton stream is attenuated to the single-photon level and fourth-order interference is measured. From it the authors directly retrieve near transform-limited pulse durations without amplification or dispersion management. The result stayed accurate after propagation through 25 kilometers of standard fiber.
The same interferogram gives access to temporal separations in multisoliton states. Intersoliton separations turn into additional interference dips at the corresponding delays, which enabled subpicosecond characterization of the intracavity temporal structure. science.org
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The authors describe the approach as immune to amplification and dispersion distortions and as a tool for studying complex soliton physics. The work is a laboratory demonstration of the measurement method.
