Showing papers by "Hongyu Luo published in 2023"

Q-switched Er3+/Dy3+ codoped ZrF4 fiber laser: continuously tunable pulse generation from 3.06 to 3.62 µm

Abstract: In this Letter, we report on widely tunable pulse generation from a red-diode-clad-pumped mid-infrared (mid-IR) Er3+/Dy3+ codoped ZrF4 fiber laser, for the first time, to the best of our knowledge. Using a Fe2+:ZnSe crystal, continuously tunable Q-switched pulses across the range of 3.06–3.62 µm have been attained, which not only represents the widest range (in wavelength domain) from a pulsed rare-earth-doped fiber laser at any wavelength, but also almost entirely covers the strong absorption band of C-H bonds in the mid-IR, providing a potential way for gas detection and polymer processing. In addition, the commercial InAs quantum-well-based saturable absorbers (SAs) have been employed instead, and the obtained longest Q-switching wavelength of 3.39 µm is slightly shorter than 3.444 µm determined by its nominal direct bandgap of 0.36 eV.

Near-infrared pumped, octave-tunable, on-chip mid-infrared Raman soliton source.

Abstract: This article proposes and numerically demonstrates a widely tunable on-chip Raman soliton source based on a cascaded As2Se3 waveguide. The cascaded sub-waveguides (input and output) with varying widths act as nonlinear devices, while a tapered waveguide is arranged between them to achieve low-loss transmission. The input waveguide provides anomalous dispersion in the near-infrared band, thereby enabling the 1.96 µm source for Raman soliton self-frequency shift (SSFS) pumping. The output waveguide exhibits large anomalous dispersion and good mode confinement in the mid-infrared band thus supporting further SSFS process. A 2.29∼4.57 µm tunable Raman source is theoretically realized in this on-chip platform. This work presents a simple and easy-to-implement strategy to extend the tuning range of on-chip sources. Notably, to the best of our knowledge, this is the first demonstration of the cascading strategy for SSFS process in an on-chip platform. The proposed tunable source has great potential in integrated spectroscopy, gas sensing, and LiDAR applications.

Efficient Raman pulse fiber laser pumped by a dissipative soliton resonance pulse near 2 µm.

Abstract: A high-efficiency Raman conversion from 1.987 µm to 2.177 µm is demonstrated experimentally in 45 m GeO2-doped silica fiber, adopting a dissipative soliton resonance (DSR) rectangular pulse as the pump. Over the entire spectral distribution, the spectral purity of the first-order Raman pulse is up to 96.8%, suggesting a nearly complete pump depletion before the onset of cascaded Raman shifts. The corresponding pump-to-Raman conversion efficiency of 67.4% is the highest up to date in this spectral region. Meanwhile, a large Raman pulse energy of 1.03 µJ was obtained at the repetition rate near MHz level, corresponding to 0.893 W average power. In the total output, the Raman-dominated spike has a Full Width Half Maximum (FWHM) of 1.18 ns far narrower than DSR's pulse duration of 10.25 ns. The results indicate that DSR is a promising candidate for developing efficient Raman nanosecond pulse fiber laser in mid-infrared (MIR) region.

Efficient cascaded Raman pulse generation in an all-fiber configuration based on 2 μm electronically modulated pulse pumping

Abstract: Stimulated Raman Scattering (SRS) is an important nonlinear process in optical fibers that can realize the MIR wavelength shift from our existing pump source. In this paper, we experimentally investigated an efficient 2.19- and 2.42 μm cascaded Raman pulse fiber laser that was composed of 2 μm electronically modulated pulse source, one typically three-stage Tm-doped fiber amplifier and a segment of commercially nonlinear fiber. A simple single-pass configuration was built to avoid the bandwidth limitation of optical components for Raman pulse generation at longer wavelengths.