Saturable absorption properties and ultrafast photonics applications of HfS3.

In this Letter, we focus on investigating the ultrafast photonics applications of two-layer HfS3 nanosheets. We prepared two-layer HfS3 nanosheets and carried out experiments to study their nonlinear saturable absorption properties. The results showed that the two-layer HfS3-based saturable absorber exhibited a modulation depth of 16.8%. Additionally, we conducted theoretical calculations using first principles to estimate the structural and electronic band properties of the two-layer HfS3 material. Furthermore, we utilized the two-layer HfS3 materials as SAs in an erbium-doped fiber cavity to generate mode-locked laser pulses. We measured a repetition frequency of 8.74 MHz, a pulse duration of 540 fs, and a signal-to-noise ratio of 77 dB. Overall, our findings demonstrate that the two-layer HfS3 material can serve as a reliable saturable absorber, possessing properties comparable to currently used two-dimensional materials. This expands the application fields of HfS3 materials and highlights their potential for advanced optoelectronic devices.

A mini-review on gene delivery technique using nanoparticles-mediated photoporation induced by nanosecond pulsed laser.

Nanosecond pulsed laser induced photoporation has gained increasing attention from scholars as an effective method for delivering the membrane-impermeable extracellular materials into living cells. Compared with femtosecond laser, nanosecond laser has the advantage of high throughput and low costs. It also has a higher delivery efficiency than continuous wave laser. Here, we provide an extensive overview of current status of nanosecond pulsed laser induced photoporation, covering the photoporation mechanism as well as various factors that impact the delivery efficiency of photoporation. Additionally, we discuss various techniques for achieving photoporation, such as direct photoporation, nanoparticles-mediated photoporation and plasmonic substrates mediated photoporation. Among these techniques, nanoparticles-mediated photoporation is the most promising approach for potential clinical application. Studies have already been reported to safely destruct the vitreous opacities in vivo by nanosecond laser induced vapor nanobubble. Finally, we discuss the potential of nanosecond laser induced phototoporation for future clinical applications, particularly in the areas of skin and ophthalmic pathologies. We hope this review can inspire scientists to further improve nanosecond laser induced photoporation and facilitate its eventual clinical application.

InSb-based saturable absorbers for ultrafast photonic applications.

Sb-related III-V compounds have recently gained great research interest owing to their excellent optical and electrical characteristics, which provide many possibilities in photonics and electronics. This study investigated the application of InSb films in ultrafast photonics. An InSb film was fabricated on the tapered zone of a microfiber, and its saturation intensity, modulation depth, and non-saturable loss were determined as 119.8 MW cm-2, 23.5%, and 27.3%, respectively. The structure of the electronic band and density of states of InSb were theoretically calculated. Notably, mode-locked and Q-switched fiber lasers were realised by incorporating the InSb-microfiber device into two different Er-doped fiber cavities. In the Q-switching state, the narrowest pulse duration was measured as 1.756 µs with a maximum single-pulse energy of 221.95 nJ and a signal-to-noise ratio of 60 dB. In the mode-locking operation, ultrafast lasers with a high signal-to-noise ratio (70 dB), a pulse width as narrow as 265 fs and a repetition rate of 49.51 MHz were acquired. Besides, the second-harmonic mode-locked state was built with an output power of 13.22 mW. In comparison with the reported laser performance with 2D materials as saturable absorbers, the InSb-based mode-locked and Q-switched fiber lasers proposed herein exhibit better comprehensive performance.

GaSb Film is a Saturable Absorber for Dissipative Soliton Generation in a Fiber Laser.

Nanotechnology is at the forefront of scientific research and offers great prospects for the development of technology. As a type of III-V semiconductor, GaSb materials exhibit numerous outstanding optical and electrical characteristics that are very promising for nonlinear optical device applications. In this study, the electronic band structures of GaSb are theoretically calculated, and its application in dissipative soliton fiber lasers is validated. A GaSb thin film is deposited on a microfiber using magnetron sputtering deposition, and the morphology, chemical composition, structure, and nonlinear optical characteristics of the proposed microfiber-GaSb device are investigated. After incorporating it into an Er-doped fiber laser, dissipative soliton laser pulses are readily obtained with a fundamental frequency of 43.5 MHz. With increasing pump power, the fiber laser could work in the fundamental frequency mode-locking state. At a pump power of 570 mW, the pulse width and the output power are measured to be 917 fs and 49.75 mW, separately. These results reveal that GaSb can be used as an efficient saturable absorber, which will have potential applications in ultrafast optics.

Ultrafast Photonics of Ternary RexNb(1-x)S2 in Fiber Lasers.

Two-dimensional (2D) transition metal chalcogenides (TMCs) become more attractive upon addition of a third element owing to their unique structure and remarkable physical and chemical properties, which endow these materials with considerable potential for applications in nanoscale devices. In this work, a RexNb(1-x)S2-based saturable absorber (SA) device for ultrafast photonics applications is studied. The device is assembled by placing RexNb(1-x)S2 nanosheets with a thickness of 1-3 nm onto a microfiber to increase their compatibility with an all-fiber laser cavity. The prepared RexNb(1-x)S2-based device exhibits a modulation depth of 24.3%, a saturation intensity of 10.1 MW/cm2, and a nonsaturable loss of 28.5%. Furthermore, the RexNb(1-x)S2-based device is used to generate ultrashort pulses in an erbium-doped fiber (EDF) laser cavity. At a pump power of 260 mW, the EDF laser operates in a conventional soliton mode-locked region. The pulse width is 285 fs, and the repetition frequency is 61.993 MHz. In particular, the bound-state soliton mode-locking operation is successfully obtained in a pump power range of 300-900 mW. The bound-state pulses are formed by doubling identical solitons with a temporal interval of 0.8 ps. The output power is as high as 47.9 mW, and the repetition frequency is 123.61 MHz. These results indicate that the proposed RexNb(1-x)S2-based SAs have comparable properties to currently used 2D SAs and provide a basis for their application in the field of ultrafast photonics.

WxNb(1-x)Se2 nanosheets for ultrafast photonics.

Ternary transition metal chalcogenides (TTMDCs), a novel type of two-dimensional (2D) three-element materials, possess multiple physical and chemical properties and have promising potentials in basic physics and devices. Herein, the usage of WxNb(1-x)Se2 nanosheets as a rising ultrafast photonic device to generate high power mode-locked and Q-switched pulses in a fiber laser is demonstrated. The WxNb(1-x)Se2 nanosheets were successfully prepared by the liquid exfoliation method with thickness less than 3 nm. The nonlinear optical absorption of the WxNb(1-x)Se2-based device was investigated with the saturable intensity of 40.93 MW cm-2 and modulation depth of 5.43%. After integrating the WxNb(1-x)Se2-based device into an Er-doped fiber (EDF) laser cavity, mode-locking and Q-switching laser pulses were formed. In the mode-locked mechanism output, the pulse width is as narrow as 131 fs and the output power is 52.93 mW. In Q-switched operation, the shortest pulse duration is 1.47 µs with the largest pulse energy of 257 nJ. Compared to recent studies, our results showed some improvements. This study suggests that 2D TTMDC-based devices could be developed as efficient ultrafast photonics candidates and widely used in nonlinear optical applications.

Vanadium disulfide for ultrafast photonic application.

The investigation of two-dimensional (2D) nonlinear optical materials offers a promising way to construct the high-performance optical devices in fundamental and industrial applications because of their rich distinct optoelectronic properties. Herein, by utilizing the liquid exfoliation method, vanadium disulfide (VS2) nanosheets are prepared and the thickness is measured to be 3.16 nm. In addition, we have fabricated the VS2-based optical device and the nonlinear optical property is characterized with modulation depth of 23.97%. By using VS2 as saturable absorber, a high stable passively mode-locking Er-doped fiber laser is obtained with pulse duration of 169 fs and the largest average output power of 70.5 mW. The slope efficiency is up to 7.9%. In comparison to recent results of mode-locking fiber lasers with 2D materials, the VS2-based fiber laser demonstrates better performance. To the best of our knowledge, this is the first example of using VS2 for generating femtosecond mode-locked laser pulse. Our experimental results not only reveal VS2 ultrafast photonics application, but also advance the high-performance applications for information science and nonlinear optics.

Niobium disulfide as a new saturable absorber for an ultrafast fiber laser.

Group VB transition metal dichalcogenides (TMDCs) are emerging two-dimensional materials and have attracted significant interests in the fields of physics, chemistry, and material sciences. However, there are very few reports about the optical characteristics and ultrafast photonic applications based on group VB TMDCs so far. In this work, we have calculated the niobium disulfide (NbS2) band structure by the density functional theory (DFT), which has revealed that NbS2 is a metallic TMDC. In addition, we have prepared an NbS2-microfiber device and the nonlinear optical characteristics have been investigated. The modulation depth, saturation intensity and non-saturable loss have been measured to be 13.7%, 59.93 MW cm-2 and 17.74%, respectively. Based on the nonlinear optical modulation effect, the Er-doped fiber (EDF) laser works in the soliton mode-locking state with the pump power of 94-413 mW. The pulse duration of 709 fs and the maximum average output power of 23.34 mW have been obtained at the pump power of 413 mW. The slope efficiency is as high as 6.79%. Compared to the recently reported studies based on TMDCs comprehensively, our experimental results are better. These experimental results demonstrate that NbS2 with excellent nonlinear optical properties can be used as a promising candidate to advance the development of ultrafast photonics.

Effects of Different 980-nm Diode Laser Parameters in Hepatectomy.

BACKGROUND AND OBJECTIVE: Despite the successful application of laser in animal experiments and clinics, the adjustment of laser parameters during surgery is still unclear. This study aimed to investigate the effect of different 980-nm diode laser parameters in hepatectomy. This could provide a clear protocol for using 980-nm diode laser in hepatectomy. STUDY DESIGN/MATERIALS AND METHODS: In total, 48 Sprague-Dawley rats were used to explore the effects of different 980-nm diode laser parameters in hepatectomy, by setting different parameter combinations. The rats were randomly divided into eight groups, including the continuous wave group and quasi-continuous wave group. The effects were assessed in terms of liver resection speed, extent of intraoperative bleeding, and thermal damage. RESULTS: In the quasi-continuous wave group, there was a significant difference in resection speed at the different laser parameters (P < 0.001); however, there was no significant difference in intraoperative bleeding and thermal damage. In the continuous wave group, there was a significant difference in resection speed, intraoperative bleeding, and thermal damage at different parameters. CONCLUSION: The study showed that the average power determined hemostasis efficiency and thermal damage, and peak power determined the liver resection speed, whereas the pulse width and repetition frequency are not independent factors. When using 980-nm diode laser in hepatectomy, the average power should be decreased to prove hemostasis efficiency in delicate operations, and the peak power should be decreased to accelerate the procedure without worsening thermal damage. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Tungsten disulphide for ultrashort pulse generation in all-fiber lasers.

Tungsten disulphide (WS2), which exhibits excellent saturable absorption properties, has attracted much attention in the applications of photonic devices. In this paper, WS2 is applied for the preparation of a saturable absorber (SA). Using the pulsed laser deposition (PLD) method, WS2 is deposited on the side surface of the tapered fiber. In order to obtain larger non-linearity of the SAs with evanescent wave interaction, the tapered fiber had a smaller waist diameter and longer fused zone. Gold film was deposited on the fiber-taper WS2 SAs to improve their reliability and avoid oxidation and corrosion. Employing the balanced twin-detector method, the modulation depth of the fiber-taper WS2 SAs was measured to be 17.2%. With the fiber-taper WS2 SA, a generated pulse with 246 fs duration and a 57 nm bandwidth was obtained at 1561 nm. The electrical signal to noise ratio was better than 92 dB. To our knowledge, the pulse duration was the shortest among the reported all-fiber lasers with transition metal dichalcogenide (TMD) SAs. These results indicate that fiber-taper WS2 SAs with smaller waist diameter and longer fused zone are promising photonic devices for ultrashort pulse generation in all-fiber lasers.

Tungsten disulfide saturable absorbers for 67 fs mode-locked erbium-doped fiber lasers.

In this paper, we demonstrate 67 fs pulse emitting with tungsten disulfide (WS2) in mode-locked erbium-doped fiber (EDF) lasers. Using the pulsed laser deposition method, WS2 is deposited on the surface of the tapered fiber to form the evanescent field. The fiber-taper WS2 saturable absorber (SA) with the large modulation depth is fabricated to support the ultrashort pulse generation. The influences of the WS2 SA are analyzed through contrastive experiments on fiber lasers with or without the WS2 SA. The pulse duration is measured to be 67 fs, which is the shortest pulse duration obtained in the mode-locked fiber lasers with two dimensional (2D) material SAs. Compared to graphene, topological insulator, and other transition metal dichalcogenides (TMDs) SAs, results in this paper indicate that the fiber-taper WS2 SA with large modulation depth is a more promising photonic device in mode-locked fiber lasers with the wide spectrum and ultrashort pulse duration.

Ultra-stability Yb-doped fiber optical frequency comb with 2 × 10-18/s stability in-loop.

We demonstrate a full control ultra-stability Yb-doped fiber optical frequency comb (OFC). The carrier-envelop offset frequency (fceo) and the repetition rate (fr) are locked with the standard phase locked loop (PLL) technique. The fceo is locked to the radio frequency (RF) synthesizer, and the Allan deviation is 1.2 × 10-17/s. The fr is locked to an ultra-stability continuous wave (CW) laser at 972 nm. The beat signal (fbeat) between the Yb-doped fiber OFC and CW laser is obtained with the signal to noise ratio (SNR) of 43 dB at 300 kHz resolution bandwidth (RBW). The time jitter of the fbeat signal is 278 as, which is integrated from 1 Hz to 10 MHz. The long-term stability is 575 µHz in 3 hours, and the corresponding Allan deviation is 2 × 10-18/s, which is the best stability result in Yb-doped fiber OFC. The linewidth is narrowed from 200 kHz to subhertz magnitude limited by the instrument resolution bandwidth.

Novel asymmetric representation method for solving the higher-order Ginzburg-Landau equation.

In ultrafast optics, optical pulses are generated to be of shorter pulse duration, which has enormous significance to industrial applications and scientific research. The ultrashort pulse evolution in fiber lasers can be described by the higher-order Ginzburg-Landau (GL) equation. However, analytic soliton solutions for this equation have not been obtained by use of existing methods. In this paper, a novel method is proposed to deal with this equation. The analytic soliton solution is obtained for the first time, and is proved to be stable against amplitude perturbations. Through the split-step Fourier method, the bright soliton solution is studied numerically. The analytic results here may extend the integrable methods, and could be used to study soliton dynamics for some equations in other disciplines. It may also provide the other way to obtain two-soliton solutions for higher-order GL equations.

70-fs mode-locked erbium-doped fiber laser with topological insulator.

Femtosecond optical pulses have applications in optical communication, astronomical frequency combs, and laser spectroscopy. Here, a hybrid mode-locked erbium-doped fiber (EDF) laser with topological insulator (TI) is proposed, for the first time to our best knowledge. The pulsed laser deposition (PLD) method is employed to fabricate the fiber-taper TI saturable absorber (TISA). By virtue of the fiber-taper TISA, the hybrid EDF laser is passively mode-locked using the nonlinear polarization evolution (NPE), and emits 70 fs pulses at 1542 nm, whose 3 dB spectral width is 63 nm with a repetition rate and transfer efficiency of 95.4 MHz and 14.12%, respectively. Our experiments indicate that the proposed hybrid mode-locked EDF lasers have better performance to achieve shorter pulses with higher power and lower mode-locking threshold in the future.

Generation of dark solitons in erbium-doped fiber lasers based Sb(2)Te(3) saturable absorbers.

Dark solitons, which have better stability in the presence of noise, have potential applications in optical communication and ultrafast optics. In this paper, the dark soliton formation in erbium-doped fiber lasers based Sb(2)Te(3) saturable absorber (SA) is first experimentally demonstrated. The Sb(2)Te(3) SA is fabricated by using the pulsed laser deposition method. The generated dark solitons are centered at the wavelength of 1530 nm and repetition rate of 94 MHz. Analytic solutions for dark solitons are also obtained theoretically.

Observation of soliton fission in microstructured fiber.

Femtosecond pulse propagation at λ=802 nm; in microstructured fiber (MF) with zero-dispersion wavelength at 780 nm is studied experimentally and numerically. The temporal and spectral distributions of the femtosecond pulse in MF are demonstrated by using a grating-eliminated no-nonsense observation of ultrafast incident laser light e-fields technique. Soliton fission is directly observed in the experimental results. The simulation of soliton evolution with the propagation distance in time and frequency domain is conducted.