In this Letter, we present the mode-locking operation of a 2.87 µm H o 3 + / P r 3 + codoped fluoride fiber laser, helped by the ultrafast nonlinear optical absorption behavior of gold nanowires (GNWs). The mode locker is fabricated by depositing the GNW solution onto a silver mirror. It has a modulation depth of 14.2%, a saturation intensity of 26.2 M W / c m 2 , and a non-saturation loss of 29.9% at 2.87 µm. With an increased pump power, the laser operates in Q -switched mode-locking, fundamental mode-locking, and harmonic mode-locking (HML) states. This represents the first, to our knowledge, mid-infrared mode-locked laser using gold nanomaterials. Additionally, the HML is also the first observation in a laser in this band using material saturable absorbers, implying the capability of GNWs for high repetition rate generation.

Graphene/WS2 (G/WS2) van der Waals (vdW) heterostructures are utilized as saturable absorbers (SAs) in compact mode-locked fiber lasers operating in the telecommunication L-band for the first time. The interlayer coupling is confirmed by Raman and photoluminescence spectra. In comparison with pure WS2, the heterostructure exhibits excellent nonlinear optical properties in terms of larger modulation depth and lower saturation intensity due to the strong interlayer coupling. By incorporating the G/WS2-based SA into an all-anomalous-dispersion fiber laser, stable conventional-soliton pulses with a pulse duration down to 660 fs can be realized at 1601.9 nm, manifesting better output performance compared to pure WS2. In addition, through shifting the cavity dispersion to the net-normal dispersion, the G/WS2 SA can also be applied for dissipative-soliton generation. Resultant output pulses feature the central wavelength of 1593.5 nm and the pulse duration of 55.6 ps. Our results indicate that the G/WS2 vdW heterostructure is a promising candidate as SA for pulsed laser applications, which pave the way for the development of novel ultrafast photonic devices with desirable performance.

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A Fourier domain mode locking (FDML) optoelectronic oscillator (OEO) based on stimulated Brillouin scattering (SBS) is proposed to generate complementary linearly chirped microwave waveform (LCMW) pairs with flexibly-reconfigurable frequency sweep range and excellent frequency sweep linearity. The FDML OEO involves an SBS-based dual-passband microwave photonic filter with its two passbands linearly and fast scanning in the opposite direction at an identical frequency sweep rate, which is realized by using a single laser source to obtain a fast frequency sweep probe light and a two-tone pump light through electro-optic modulation. A proof-of-concept experiment is carried out to demonstrate the proposed scheme. In the experiment, frequency-sweep-range-reconfigurable complementary LCMW pairs with period of 20.5 µs are generated in the range of 5 GHz to 18 GHz, where the maximum time-bandwidth product and chirp rate are 82000 and ±0.195 GHz/µs, respectively. Most importantly, the frequency sweep linearity is measured to be 1.76%, which is much better than the results obtained in the existing FDML OEOs.

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This paper presents the balanced-to-balanced Gysel filtering power divider with arbitrary power division for first time. Based on the multicoupled series-resonator bandpass prototype network, a detailed theory analysis is presented and the corresponding design equations are concluded. Two filtering power dividers with the division ratio of 2 and 3 are realized using the half-wavelength resonator and the short-stub-loaded resonator. Finally, two example circuits are fabricated and measured for verification. The measured results show good agreement with the simulated and confirm the theory. INDEX TERMS Balanced-to-balanced power divider, bandpass filtering response, arbitrary power division, Gysel power divider.

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