Single-photon time-resolved measurements are of great importance in broad application fields, such as ultrafast phenomena, sensing, and quantum information science. Single-photon detectors have limited, temporal resolution, hence, there is need for novel approaches. In this study, we developed an asynchronous optical sampling technique for single-photon time-resolved cross-correlation measurements using a dual-wavelength comb. Employing slightly different repetition frequencies, high-speed and high-time resolution detection was achieved without the need for a mechanical delay stage. Using distinct-color combs for the signal and pump pulses, highly sensitive detection was achieved by efficiently suppressing the strong background caused by the high-power pump. Furthermore, we experimentally demonstrated femtosecond time-resolved measurements at the single-photon level. The signal and pump pulses were derived from the Er and Yb fiber combs. The center wavelengths of the comb were 1560 and 1050 nm, and their repetition frequencies were 107 and 750 MHz. Signal pulses were attenuated to the single-photon level, and the pump pulses were amplified to 1.3 W. The high power and high repetition frequency of the pump enabled highly efficient nonlinear time gating. Temporal characteristics of a weak signal pulse is obtained by photon counting of the generated sum frequency light of the signal and pump using a nonlinear crystal. We obtained the temporal profiles of the single-photon Er comb pulses as a cross-correlation waveform with a half-width of 173 fs and measured the higher-order chirp of a single-photon femtosecond pulse. The developed technique is promising for single-photon-level ultrafast optical applications.
The nonclassical light sources, such as frequency-time entangled photons, are anticipated to offer significant benefits for emerging quantum optical sensing or spectroscopic measurements and manifest on ultrafast time scales (sub-ps to fs). However, the constrained time resolution (ns to ps) of photon-counting detectors poses challenges in comprehensively characterizing their detailed properties on ultrafast time scales. Therefore, we present a novel asynchronous optical sampling (ASOPS) technique utilizing two-color optical frequency combs to demonstrate highly precise and sensitive ultrafast time-resolved cross-correlation measurements at the single-photon level. By employing photon counting statistics, this method successfully reconstructed the picosecond pulse width cross-correlation waveforms at extremely low power level (<1 photon per pulse), while effectively suppressing the residual temporal jitter between the two combs via optically triggered averaging using asynchronous optical sampling of combs. The use of repetition frequency stabilized distinct-wavelength pulses allowed for the effective suppression of strong background light from the pump through spectral filtering, achieving single-photon sensitivity. Subsequently, we parametrically down converted the frequency doubled light from the Er comb in the nonlinear ppKTP waveguide to generate quantum entangled photons at telecom band. A 9.04% Klyshko efficiency with a photon pair generation rate of 0.98 MHz/mW was obtained using heralding detection. Employing the established ASOPS technique to the generated photon pairs enabled the realization of ultrafast time-resolved and quantum mechanical correlation measurements. This paves the way for a versatile and comprehensive manipulation of quantum-entangled photon pairs in the time-domain, with potential applications in ultrafast optical quantum technology and ultrashort fluorescence measurements.
Precision frequency metrology and attosecond pulse generation critically rely on stabilization of the carrier-envelope phase (CEP) of mode-locked lasers. So far, only a relatively small class of lasers has been successfully stabilized to warrant phase jitters of a few hundred milliradians as they are required for the generation of an isolated attosecond pulse. For stabilizing certain laser types, the exact reasons for the observed difficulties (or the lack thereof) is only poorly understood. Here we compare the free-running CEP noise of four different lasers, including a femtosecond Ti:sapphire laser and three mode-locked fiber lasers. This study indicates a correlation between amplitude and frequency fluctuations at low Fourier frequencies for essentially all lasers investigated. This finding is well explained with technical noise sources and thermal coupling mechanisms below the upperstate lifetime of the laser gain material. However, for one of the lasers under test, we observe a broadband amplitude-to-phase coupling mechanism well above the upperstate lifetime. This coupling mechanism is related to a dynamical loss modulation. We verify our explanation by numerical simulations, which identify resonances of the saturable absorber mirror as a possible explanation for the coupling mechanism. In case of high modulation depth and resonantly enhanced saturation characteristics, such a saturable absorber can give rise to broadband conversion of spontaneous emission amplitude noise into phase noise, which may cause, in turn, extremely broadband noise signatures, exceeding a megahertz bandwidth.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.