Utilizing bismuth telluride (Bi₂Te₃) nanosheet saturable absorbers (SA), a remarkable source of continuous-wave infrared radiation known for its high efficiency and wide range of accessible wavelengths, has been successfully developed. The mode-locking bright pulses have a repetition frequency of 9.5 MHz and a pulse width of 0.6 ps at a power level of 203.5 mW. The optical spectrum has its center at 1050.23 nm and delivers pulse energies of 2.13 nJ and output power of 20.3 mW. Using a straightforward 18 m long ring design and a laser cavity with a −19.9 ps²/km dispersion, a 44 dB signal-to-noise ratio (SNR) was achieved to demonstrate the pulse’s strong stability.

In this work, we present the generation of two distinct types of soliton pulses using a Bismuth Selenide (Bi₂Se₃) saturable absorber (SA) synthesized in our laboratory. The soliton pulses were generated in two different laser cavity configurations, resulting in two types of solitons: a soliton pulse with Kelly sidebands and a bunched soliton pulse with peak-dip sidebands. Both solitons operated at the fundamental repetition rate—23.3 MHz (for the soliton with Kelly sidebands) and 13 MHz (for the bunched soliton with peak-dip sidebands). We observed that the accumulation of nonlinear phase shift from the added single mode fiber (SMF) split the single soliton pulse into 44 pulses in a bunched oscillation envelope. At the same time, peak-dip sidebands were imposed on the bunched soliton spectrum due to constructive and destructive interferences between soliton pulse and dispersive waves. The measured pulse width for both solitons were 0.63 ps (for the soliton with Kelly sidebands) and 1.52 ps (for the bunched soliton with peak-dip sidebands), respectively. Our results demonstrate the potential of Bi₂Se₃ SAs in generating different types of soliton pulses, which could have potential applications in various areas of optical communication and spectroscopy.

Multi-wavelength fiber laser has great potential for use in dense wavelength-division multiplexing (DWDM) systems, sensors, and microwave photonics. This paper presents a multi-wavelength Brillouin erbium fiber laser (MW-BEFL) with double-frequency Brillouin spacing of approximately 0.176 nm between each adjacent Stokes. The proposed setup utilizes double cavities configuration for odd and even-order Brillouin Stokes to propagate separately in the system. This configuration is flexible as it can be transformed into a single-spacing MW-BEFL by swapping the ports of the circulator; it can also extract the odd-orders Brillouin Stokes by relocating the OSA in the cavity. Up to 25 double-spaced Brillouin Stokes are obtained with a tuning range of 30 nm. The first 8 Stokes have peak power variation within ± 3.7 dB and an average signal-to-noise ratio of 20 dB.

Light polarization rotation plays an important role in modern optical science and engineering. As the 980 nm laser diode pump power was increased, Ge ₄ Bi ₇ Te absorbed energy and raised the temperature of Ge ₄ Bi ₇ Te. The refractive index of Ge ₄ Bi ₇ Te varied with the temperature change in the material, driven by the thermo-optic effect. When Amplified Spontaneous Emission (ASE) source was injected into the proposed setup, its azimuth varied linearly from -89.92° to -71.26°. Total azimuth rotation was estimated at 18.66°, and the rotation efficiency was ascertained at 0.0531°/mW. This work demonstrates the use of Ge ₄ Bi ₇ Te to achieve controllable polarization, highlighting its potential as a promising material for optical imaging, sensing and communication.

Over the past decades, lasers operating in the mid-infrared (MIR) region have attracted considerable attention because of their wide-ranging applications. In particular, fiber lasers operating near the 2 μm wavelength have attracted significant interest for use in fields such as biomedical, optical communications, and remote sensing. This chapter focuses on the development of fiber lasers operating in the 2 μm region, with an emphasis on pulsed laser operation in the near-MIR region using MXene-based thin-film saturable absorbers (SAs). In this study, niobium carbide-based (Nb₂CT_x) MXenes are employed as the SA material, fabricated with two different host polymers: polyvinyl alcohol (PVA) and polyethylene oxide (PEO). These Nb₂CT_x-based thin-film SAs were integrated into the laser cavity by sandwiching them between fiber ferrules; they successfully generated Q-switched operation in a thulium-doped fiber laser (TDFL) system within the near-MIR region. This work presents the first reported implementation of a Q-switched TDFL using Nb₂CT_x-PEO as a saturable absorber. The demonstrated Q-switched operation achieved pulse widths of 1.995 and 1.942 μs for Nb₂CT_x-PEO and Nb₂CT_x-PVA, respectively, both significantly shorter than the 13.3–4.4 μs range reported in earlier studies, highlighting the effectiveness of these MXene-based SAs for pulsed laser generation at 2 μm.