Dual-comb spectroscopy holds the promise as real-time, high-resolution spectroscopy tools. However, in its conventional schemes, the stringent requirement on the coherence between two lasers requires sophisticated control systems. By replacing control electronics with an all-optical dual-comb lasing scheme, a simplified dual-comb spectroscopy scheme is demonstrated using one dual-wavelength, passively mode-locked fiber laser. Pulses with a intracavity-dispersion-determined repetition-frequency difference are shown to have good mutual coherence and stability. Capability to resolve the comb teeth and a picometer-wide optical spectral resolution are demonstrated using a simple data acquisition system. Energy-efficient, free-running fiber lasers with a small comb-tooth-spacing could enable low-cost dual-comb systems.

We demonstrate a dual-wavelength passively mode-locked soliton fiber laser based on the single-wall carbon nanotube saturable absorber. By using a simple scheme of adjusting the intracavity loss, the gain profile of the erbium-doped fiber laser is effectively controlled. Besides operating at a single wavelength, the laser is able to simultaneously generate sub-picosecond pulses at both ~1532 and 1557 nm wavelength. The mode-locking wavelength can also be quickly switched from one wavelength to the other by changing the intracavity loss with a tunable attenuator.

We report simple and compact all-fiber erbium-doped soliton and dispersion-managed soliton femtosecond lasers mode-locked by the MXene Ti₃C₂T_x. A saturable absorber device fabricated by optical deposition of Ti₃C₂T_x onto a microfiber exhibits strong saturable absorption properties, with a modulation depth of 11.3%. The oscillator operating in the soliton regime produces 597.8 fs-pulses with 5.21 nm of bandwidth, while the cavity with weak normal dispersion (~0.008 ps²) delivers 104 fs pulses with 42.5 nm of bandwidth. Our results contribute to the growing body of work studying the nonlinear optical properties of MXene that underpin new opportunities for ultrafast photonic technology.

Mode-locked fiber lasers that can simultaneously generate two asynchronous ultrashort pulse trains could play an attractive role as the alternative light sources for low-complexity dual-comb metrology applications. Although a few multiplexing schemes to realize such lasers have been proposed and demonstrated, here we investigate the lasing characteristics of a passively mode-locked fiber laser with a finite amount of intracavity birefringence. By introducing a section of polarization-maintaining (PM) fiber into the otherwise-non-PM-single-mode cavity, dual asynchronous pulses with nearly orthogonal states of polarization are generated. With a repetition rate difference of hundreds of hertz, the pulses have well-overlapped spectra and show typical features of polarization-locked vector solitons. It is demonstrated that under an anomalous or net normal dispersion regime, either dual vector solitons or dual dissipative vector solitons can be generated, respectively. Such polarization-multiplexed single single-cavity dual-comb lasers could find further uses in various applications in need of simple dual-comb system solutions.

A two-dimensional symmetric hybrid plasmonic waveguide that integrates two high-refractive-index dielectric slabs with a finite-width insulator-metal-insulator (IMI) structure is proposed, and the characteristics of its long-range propagation mode are numerically analyzed at 1550 nm wavelength. In contrast to the previously studied structures, the gap between the slabs and the metal stripe and the associated field enhancement effect result in the dramatically modified modal behavior. It is shown that, under optimized configurations, the transmission loss can be reduced significantly with little change in the mode confinement capability compared to similar dielectric-loaded surface plasmon polariton waveguides. Studies on the crosstalk between adjacent such hybrid waveguides reveal the ability to increase the integration density by ~60 times compared with the traditional IMI structures when used in 3D photonic circuits. The studied waveguide could be an interesting alternative to realize high density photonic circuits.

We demonstrate a long-term stable, all-fiber, erbium-doped femtosecond laser mode-locked by a black phosphorus saturable absorber. The saturable absorber, fabricated by scalable and highly controllable inkjet printing technology, exhibits strong nonlinear optical response and is stable for long-term operation against intense irradiation, overcoming a key drawback of this material. The oscillator delivers self-starting, 102 fs stable pulses centered at 1555 nm with 40 nm spectral bandwidth. This represents the shortest pulse duration achieved from black phosphorus in a fiber laser to date. Our results demonstrate the great potential for black phosphorus as an excellent candidate for long-term stable ultrashort pulse generation.