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Due to the slowdown of Moore's law, the integrated photonic devices have provided a route to promote the development of large‐scale optical communications with high performance. As one of the essential components of optical routers, an optical switch can fast transmit or block the optical signal. However, most of the integrated optical switches reported to date rely on thermo‐, magneto‐, or electro‐optical effects, which limit applications due to slow response times, large footprint, and complexity fabrication. Here, an integrated nonlinear optical switch designed by the inverse‐design method and fabricated on the SiN platform is introduced. The integrated optical switch is demonstrated with significant intensity‐dependent transmission at 1.5 µm waveband. The polarization‐depended capability is explored by using fundamental polarized lights (transverse electric and transverse magnetic, respectively), which exhibits opposite transmission change trends during the whole power range and opens potential applications such as photonic quantum information processing. In order to address the saturation of Kerr‐nonlinearity in SiN materials at high power, a MoS2/SiN hybrid integrated optical switch is fabricated by uniformly cladding few‐layer MoS2 on the surface of inverse‐designed region. That is demonstrated to enhance the nonlinear optical response of device efficiently and achieve more excellent switching capability at high power. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials show great promise as saturable absorbers (SAs) for ultrafast fiber lasers. However, the relatively low modulation depth and poor stability of some 2D materials, such as graphene and black phosphorus, restrict their applications in the mid-infrared pulse generation. Herein, we first report a novel 2D double transition metal carbide, denoted as Mo2Ti2C3Tx MXene, as the saturable absorber (SA) for a passively Q-switched mid-infrared fiber laser. Due to the unique four-metal atomic layer structure, the Mo2Ti2C3Tx exhibits superior saturable absorption properties, particularly with a higher modulation depth (40% at 2796 nm) than most of the other reported 2D SA materials. After incorporating the MXene SA with an erbium-doped fiber system, the passively Q-switched pulses were achieved with a repetition rate of 157.3 kHz, the shortest pulse width of 370 ns, and single-pulse energy of 1.92 μJ, respectively. Such results extend the MXene-based SAs as promising candidates for advanced photonic devices. [ABSTRACT FROM AUTHOR]

Integrated photonics are expected to replace the conventional free‐space optical systems, yet there remains a challenge of low nonlinear response due to small nonlinear refractive index and short interaction length. Here, the large‐area monolayer MoS2 is used to facilitate excellent nonlinear response, and a pump strategy is proposed with respect to the spontaneous four‐wave mixing in the visible spectral range. The external pump incident from the top resonates in the GaN microdisk resonator and is thoroughly absorbed by the monolayer MoS2 to generate the four‐wave mixing pump via the excitonic photoluminescence. Being driven by the internal photoluminescence pump and enhanced by the microcavity structure, it is validated that the proposed structure well suffices efficient degenerate spontaneous four‐wave mixing generation. Since the emission spectrum can be tailored through careful temperature control, this work holds a great potential in various functionalities, not only on‐chip visible light sources but also optical field control. [ABSTRACT FROM AUTHOR]

We report a mid-infrared (MIR) spectral intensity-enhanced supercontinuum (SC) generation from a ZrF4-BaF 2-LaF3-AlF3-NaF fiber pumped by a nanosecond thulium-doped fiber laser. The spectral region covered from 1930 to 3500 nm with an average output power of 5.23 W. The average power ratio of the MIR SC for the wavelength > 2200 and > 2500 nm were 91.81% and 74.29% with respect to the total output power, respectively. The 1950-nm nanosecond seed pulses were generated from a long ring cavity based on semiconductor saturable absorber mode locker. The pulse repetition rate was 3.02 MHz with a tunable pulse duration of about 1.0 ns–3.9 ns. In addition, a 69.5-W short-wave infrared SC was obtained through a two-stage thulium-doped fiber amplifier with the spectrum extending from 1930 to 2500 nm. To the best of our knowledge, this is the first time such a spectral intensity-enhanced MIR SC directly pumped by a high-pulse-energy nanosecond thulium-doped fiber laser has been achieved. [ABSTRACT FROM PUBLISHER]

Group IVB transition metal dichalcogenides (TMDs) have attracted significant interests in photoelectronics due to their predictable superior physical properties compared to group VIB (Mo and W) TMDs. However, the nonlinear optical properties and ultrafast photonic devices based on group IVB TMDs remained unexplored so far. Herein, the nonlinear optical absorption of HfS2 nanosheets (NSs) prepared by liquid exfoliation is demonstrated. The usage of HfS2 as a new ultrafast photonic device for high‐energy and ultrashort pulse generation in a fiber laser is reported for the first time. A photonic crystal fiber (PCF) assisted deposition method is presented for the fabrication of an HfS2‐microfiber integrated saturable absorber (SA) device with precisely controllable light–matter interaction, which can benefit the output of the device. The HfS2‐microfiber SA device shows modulation depth of 15.7% and exhibits outstanding ultrashort pulse generation performance with pulse duration of 221.7 fs in the communication band. The experimental results suggest that HfS2 presents highly nonlinear optical absorption and can be developed into an excellent candidate of SA devices for the development of HfS2‐based ultrafast photonics. The nonlinear optical absorption of HfS2 nanosheets is demonstrated. Based on this nonlinear optical property, an HfS2‐based ultrafast photonic device is fabricated by integrating HfS2 with a microfiber. The usage of HfS2 for a new function of nonlinear optical materials in the generation of high‐energy and ultrashort pulses by fiber laser is reported. [ABSTRACT FROM AUTHOR]

• A compact, low power consumption phase shifter based racetrack resonator hybrid integrated with few-layer MoS 2 is demonstrated. • The phase shifter is fabricated on a low-loss SiN platform. • The phase tuning efficiency is measured as 13.24 pm/V at 1530 nm and the corresponding effective index in change is calculated to be 0.27 × 10-3 RIU (refractive index unit). • The half-wave-voltage-length product(V π L) is calculated as 0.41 V∙cm. We demonstrate a compact, low power consumption phase shifter based racetrack resonator hybrid integrated with few-layer MoS 2. The phase shifter is fabricated on a low-loss SiN platform. By using wet transfer method, the few-layer MoS 2 is transferred to the SiN waveguide, and the ionic liquid is introduced to form a capacitor configuration. In the presence of electrostatic doping, the effective index of MoS 2 -SiN waveguide can be efficiently modulated by adjusting bias voltage. The phase tuning efficiency of our device is measured as 13.24 pm/V at 1530 nm, and the corresponding V π L is calculated as 0.41 V∙cm. The results indicate that the strong light-matter interaction between few-layer MoS 2 and SiN photonic device in near-infrared waveband, which can be used for low-loss integrated optical links. [ABSTRACT FROM AUTHOR]

Ultrafast vortex beams have been successfully utilized in a wide variety of applications. Here, we report on the generation of the visible and near-infrared cylindrical vector beams with femtosecond pulse duration and tens of Watts average output power. Based on an optimized fiber chirped-pulse amplification system and second harmonic generation technology, Gaussian beams are generated at the visible and near-infrared wavelength, respectively. After mode conversion operation, the high-quality cylindrical vector beams can be obtained with a central wavelength of 1036.13 nm and maximum output power and ultrafast pulse duration of 60.49 W/824 fs for radial vector beams and 59.67 W/783 fs for azimuthal vector beams. In the visible spectral region, the output cylindrical vector beams have a maximum output power of 30.78 W (radial vector beams) and 27.46 W (azimuthal vector beams) at 515.75 nm central wavelength. The pulse durations are measured to be 262 fs for radial vector beam and 273 fs for azimuthal vector beam at the maximum output power. The results demonstrate that the proposed laser systems may pay a promising way to develop high-power femtosecond cylindrical vector beams sources in the visible and near-infrared wavelength for optical communication, super-resolution imaging and laser processing. • We report on the generation of high-quality cylindrical vector beams with femtosecond pulse duration and tens of Watts average output power in the visible and near-infrared region. • The cylindrical vector beams have a central wavelength of 1036.13 nm with maximum output power and pulse duration of 60.49 W/824 fs for radial polarization and 59.67 W/783 fs for azimuthal polarization. • After frequency conversion, the output cylindrical vector beams have a central wavelength of 515.75 nm. The maximum output power and pulse duration are measured to be 30.78 W/262 fs (radial vector beams) and 27.46 W/273 fs (azimuthal vector beams). • They are the shortest pulse duration of radially and azimuthally polarized beams with Watts-level average output power in the visible and near-infrared region. [ABSTRACT FROM AUTHOR]