arXiv subjects

Kangwen Yang

Publications and source records attributed to Kangwen Yang.

3 recordsLinked to original sources

arXiv2026

Observation of spectral mode splitting in a pump-enhanced ring cavity for mid-infrared generation

We report on experimental and theoretical investigation of mode-splitting dynamics in a ring cavity under the perturbation of fractional Bragg reflection from a periodically-poled nonlinear crystal. Counterintuitively, pronounced mode splitting in the spectral domain could been observed even with a tiny intensity reflection of 0.0003. The breaking of running-wave operation in the ring-cavity configuration resulted in comparable circulating fields in forward- and counter-propagation directions, which thus dramatically reduced the enhancing factor for the resonating field. In contrast, a linear cavity with intrinsically bidirectional operation was immune to the small intra-cavity reflection. Therefore, the linear-cavity layout could provide an expedient solution for a given internal reflection to obtain more stable and higher enhancement, which was confirmed by comparative studies of mid-infrared generation based on pump-enhanced difference frequency conversion. The underlying mechanism was further modeled by numerical simulations, which agreed well with experimental results. These findings could not only shed light on the understanding of the exotic feature of concatenated optical cavities, but also provide a useful guide to practical design of enhancement cavities for cavity-based frequency conversion with periodically-poled nonlinear crystals.

physics.optics↗

arXiv2026

High-precision passive stabilization of repetition rate for a mode-locked fiber laser based on optical pulse injection

We have proposed and implemented a novel scheme to obtain high-precision repetition rate stabilization for a polarization-maintaining mode-locked fiber laser. The essential technique lies in the periodic injection of electronically modulated optical pulses into a nonlinear amplifying loop mirror within the laser resonator. Thanks to the nonlinear cross-phase modulation effect, the injected pulses referenced to an external clock serves as a stable and precise timing trigger for an effective intensity modulator. Consequently, synchronous mode-locking can be initiated to output ultrafast pulses with a passively stabilized repetition rate. The capture range of the locking system reaches to a record of 1 mm, which enables a long-term stable operation over 15 hours without the need of temperature stabilization and vibration isolation. Meanwhile, the achieved standard deviation is as low as 100 $\mu$Hz with a 1-s sample time, corresponding to a fluctuation instability of 5.0$\times10^{-12}$. Additionally, the repetition rate stabilization performance based on the passive synchronization has been systematically investigated by varying the average power, central wavelength and pulse duration of the optical injection.

physics.optics↗

arXiv2023

Ultra-high-speed coherent anti-Stokes Raman spectroscopy with a hybrid dual-comb source

Coherent anti-Stokes Raman scattering (CARS) spectroscopy with time-delayed ultrashort pulses and a single-pixel photodetector has shown great potential for spectroscopic imaging and transient studies in chemistry and biological research. However, those systems rely on mechanical delay lines or two asynchronous optical combs with inflexible repetition frequencies, technically limiting their acquisition speeds. Here, we demonstrate a hybrid dual-comb CARS system involving a broadband fiber laser and a highly-flexible, frequency-modulated electro-optic comb. We achieve multiplex CARS spectra (2800-3200 cm-1), with a moderate resolution (22 cm-1), at a maximum refresh rate of 1 MHz, limited by the radio-frequency synthesizer we use. Fast spectroscopic CARS imaging is demonstrated for liquid mixtures. Our system enables spectral measurements in the high-wavenumber C-H stretching region at a record speed that is an order of magnitude higher than state-of-the-art systems, which may open up new opportunities for fast chemical sensing and imaging.

physics.optics↗