Towards visible-wavelength passively mode-locked lasers in all-fibre format

Huang

Advanced Optical Materials

et al. 2021

Palladium diselenide (PdSe2) exhibits considerable potential for application in broadband optoelectronic devices. In this work, the broadband nonlinear optical performance and ultrafast carrier dynamics from ultraviolet to near‐infrared of a trilayer PdSe2 are systematically studied. PdSe2 is found to achieve a giant saturable absorption performance. The modulation depth is 22.47% at 520 nm, whereas the nonsaturable loss and saturation intensity are only 3.83% and 15.47 GW cm−2, respectively, which are better than those of many 2D semiconductors. Based on these findings, a PdSe2‐based visible light thresholder is proposed, its function is to extract an undetectable pulse signal drowned in strong stochastic noise and thereby improve the signal‐to‐noise ratio. Pump–probe technique, along with first‐principles calculation and transient absorption spectra, reveals the intrinsic recombination mechanism, including Auger scattering and trap saturation. This work is expected to establish the foundation for the development of next‐generation PdSe2‐based devices in optoelectronics and visible light communication.

Section: Resultsmentioning

confidence: 99%

Broadband Nonlinear Photoresponse and Ultrafast Carrier Dynamics of 2D PdSe₂

Huang

Advanced Optical Materials

et al. 2021

Laser & Photonics Reviews

“…Under the pump power of 1750 mW, a maximum amplified power of 440 mW is obtained without any saturation, corresponding to a maximum pulse energy and peak power of 4 nJ and 280 W. Conspicuously, the overall performance is substantially enhanced compared with the performance achieved in the former work using NALM (0.3 nJ and 3.1 W). [ 29 ] The limitation on amplified power mainly stems from the damage of the ZBLAN fiber facet. Due to the relatively small diameter of the core and inner cladding, more pump power is unable to be coupled into the gain fiber.…”

Section: Resultsmentioning

confidence: 99%

“…The performance is significantly advanced compared with our previous work (0.3 nJ and 3.1 W) in visible temporal mode‐locking regime only. [ 29 ] This work offers a new way not only for ultrafast fiber lasers reaching visible wavelength, but also for exploring the dynamic characteristics of spatiotemporal mode‐locked pulses in the visible spectral region.…”

Section: Introductionmentioning

confidence: 99%

Visible‐Wavelength Spatiotemporal Mode‐Locked Fiber Laser Delivering 9 ps, 4 nJ Pulses at 635 nm

Ruan

Xiao

Zou

et al. 2022

Self Cite

Spatiotemporal mode‐locking (STML) in fiber lasers are of interest in applications such as optical communications, nonlinear imaging, and precision machining. To date, STML fiber lasers in the near‐infrared region have been well demonstrated, yet operation at visible wavelengths is still challenging. Here, a STML picosecond fiber laser at 635 nm with the implementation of Pr3+$^{3+}$/Yb3+$^{3+}$ co‐doped few‐mode fiber and nonlinear polarization rotation technology is reported. By solving the modified generalized multimode nonlinear Schrödinger equation, the 635 nm STML formation is theoretically predicted and analyzed. The stable 635 nm STML with a 9 ps pulse duration, which is two orders of magnitude narrower than previously reported, is realized experimentally. Moreover, spatiotemporal profiles are illustrated by investigating the locking of transverse and longitudinal modes simultaneously. By further establishing visible ultrafast fiber amplifier, the 635 nm average power is boosted up to 440 mW, corresponding to a maximum pulse energy and peak power of 4 nJ and 280 W, respectively. The experimental results are in good agreement with the numerical simulations. This work helps to understand nonlinear dynamics in STML fiber laser and directly generate large‐energy ultrashort pulses in visible region.

“…From an application perspective, the proposed scheme is capable of producing near-chirp-free solitons in normal-dispersion cavities without external compression, especially attractive for wavelength below 1.3 μm where silica fiber dispersion is typically normal 50 – 52 . Such principle can be extended to propagate near-chirp-free soliton over long distance in normal-dispersion regimes with periodically spaced SMF and PMF.…”

Section: Discussionmentioning

confidence: 99%

Phase-matching-induced near-chirp-free solitons in normal-dispersion fiber lasers

Mao

et al. 2022

Light Sci Appl

Direct generation of chirp-free solitons without external compression in normal-dispersion fiber lasers is a long-term challenge in ultrafast optics. We demonstrate near-chirp-free solitons with distinct spectral sidebands in normal-dispersion hybrid-structure fiber lasers containing a few meters of polarization-maintaining fiber. The bandwidth and duration of the typical mode-locked pulse are 0.74 nm and 1.95 ps, respectively, giving the time-bandwidth product of 0.41 and confirming the near-chirp-free property. Numerical results and theoretical analyses fully reproduce and interpret the experimental observations, and show that the fiber birefringence, normal-dispersion, and nonlinear effect follow a phase-matching principle, enabling the formation of the near-chirp-free soliton. Specifically, the phase-matching effect confines the spectrum broadened by self-phase modulation and the saturable absorption effect slims the pulse stretched by normal dispersion. Such pulse is termed as birefringence-managed soliton because its two orthogonal-polarized components propagate in an unsymmetrical “X” manner inside the polarization-maintaining fiber, partially compensating the group delay difference induced by the chromatic dispersion and resulting in the self-consistent evolution. The property and formation mechanism of birefringence-managed soliton fundamentally differ from other types of pulses in mode-locked fiber lasers, which will open new research branches in laser physics, soliton mathematics, and their related applications.