The nonlinear optical responses of two-dimensional (2D) few-layer tin diselenide (SnSe2) have been investigated in this work. By applying the Z-scan technique, the saturable absorption of SnSe2 thin film has been observed at a wavelength of ~1μm, which enables SnSe2, a new saturable absorber for pulsed laser generation. A detailed exploration of the nonlinear absorption of SnSe2 film and their dependence on excitation pulse energy is carried out. Our results show that saturation intensity of the nonlinear absorption is ~23.78 GW/cm2 and corresponding nonlinear absorption coefficients are at a range from -13596 to -2967.3 cm/GW. By employing the SnSe2-coated mirror as a saturable absorber, the passively Q-switched lasing has been achieved on a crystalline waveguide platform at ~1 μm.
Two-dimensional (2D) materials have generated great interest in the past few years opening up a new dimension in the development of optoelectronics and photonics. In this paper, we demonstrate 6.5 GHz fundamentally Q-switched mode-locked lasers with high performances in the femtosecond laser-written waveguide platform by applying graphene, MoS and BiSe as saturable absorbers (SAs). The minimum mode-locked pulse duration was measured to be as short as 26 ps in the case of BiSe SA. The maximum slope efficiency reached 53% in the case of MoS SA. This is the first demonstration of Q-switched mode-locked waveguide lasers based on MoS and BiSe in the waveguide platform. These high-performance Q-switched mode-locked waveguide lasers based on 2D materials pave the way for practical applications of compact ultrafast photonics.
The femtosecond laser micromachining of transparent optical materials offers a powerful and feasible solution to fabricate versatile photonic components towards diverse applications. In this work, we report on a new design and fabrication of ridge waveguides in LiNbO3 crystal operating at the mid-infrared (MIR) band by all-femtosecond-laser microfabrication. The ridges consist of laser-ablated sidewalls and laser-written bottom low-index cladding tracks, which are constructed for horizontal and longitudinal light confinement, respectively. The ridge waveguides are found to support good guidance at wavelength of 4 μm. By applying this configuration, Y-branch waveguiding structures (1 × 2 beam splitters) have been produced, which reach splitting ratios of ∼1:1 at 4 μm. This work paves a simple and feasible way to construct novel ridge waveguide devices in dielectrics through all-femtosecond-laser micro-processing.
The layered two-dimensional (2D) materials with extraordinary optical properties play important roles in the development of ultrafast photonics, in which mode-locking lasers with a high fundamental repetition rate (>1 GHz) are of particular interest. The nonlinear optical properties of one of the emerging 2D materials, rhenium diselenide (ReSe2), have been investigated for the first time. Broadband ultrafast saturable absorption of ReSe2 from the visible to the near infrared wavelength regimes has been observed, which enables potential applications in ultrafast lasing. With typical end-pump arrangement, continuous-wave mode-locking based on the ReSe2 saturable absorber has been realized, reaching a fundamental repetition-rate of 6.5 GHz and pulse duration as short as 29 ps at 1 μm in a monolithic waveguide platform. This work indicates intriguing applications of ReSe2 for the development of on-chip ultrafast photonic devices.
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