Abstract

This work demonstrated a high-resolution spectrum obtained from a single ultra-short high-frequency signal pulse using a new analog optical auto-correlation method that revolutionizes the signal detection and measurement technique. It provides unprecedented capability to reach the fundamental limit in Physics. This technique allows us to increase the observation/measurement time by converting a Radio Frequency (RF) signal in the optical domain and keeping the “live-signal” in a fiber-optic-recirculation-loop circuit over an extended time that could be a million times longer than the pulse width. The dispersion delay of the two RF modulation sidebands is used to perform an analog time correlation. It effectively stretches time by million times. As a result, it provides a frequency-space “snapshot” of ultra-short events without the need for a high-speed analog-to-digital converter (ADC). A single 30 ns-short two-tone pulse separated by 25 MHz was resolved in a 50 GHz wideband real-time frequency spectrum. This technique allowed us to push the physical limit in the spectral resolution of an ultra-short signal and enable a new technology to manipulate, process, and analyze ultra-short electromagnetic signals and transient events. It also provokes a fundamental question: Is the uncertainty principle limiting the frequency determination for a wave in a continuum state?

Photonic sampling analog-to-digital conversion based on time and wavelength interleaved ultra-short optical pulse train generated by using monolithic integrated LNOI intensity and phase modulator

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Single-shot cross-correlation of counter-propagating, short optical pulses using random quasi-phase-matching

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Single-shot terahertz spectroscopy using pulse-front tilting of an ultra-short probe pulse

Yoichi Kawada, Takashi Yasuda, Atsushi Nakanishi, Koichiro Akiyama, and Hironori Takahashi
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