Liquid-phase exfoliated 2D material multilayer MoS 2 is transferred onto a gold mirror and its saturable absorption at the 2 µm wavelength region is experimentally observed. This transferred MoS 2 saturable absorber has a modulation depth of 13.6% and a saturation intensity of 23.1 MW cm −2 . This saturable absorber is integrated into a linear Tm 3+ fiber laser cavity, and stable fundamental-frequency mode-locking operation is realized at 2 µm with pulse energy of 15.5 nJ, pulse width of ~843 ps, and a repetition rate of 9.67 MHz. The laser spectral width is ~17.3 nm with a center wavelength of 1905 nm. This first presence of modelocking with multilayer MoS 2 sheets in the 2 µm wavelength region verifies that multilayer MoS 2 is a good candidate for broadband mode-locking comparable to graphene, as well as a good mode-locker for achieving high pulse energy.

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Abstract-This paper presents dual-band equal/unequal Wilkinson power dividers based on a coupled-line section with short-circuited stub (called as the "coupled-line section" for short), which consists of a pair of parallel coupled lines and a short-circuited stub. With the analyses of the phase shift and equivalent characteristic impedance, the coupled-line section is used to replace the quarter-wavelength branch line in the conventional equal/unequal Wilkinson power divider to obtain excellent dual-band operation. The closed-form equations and design procedures of dual-band Wilkinson power divider are given, where one degree of design freedom is obtained and design flexibility is shown. As two examples, a dual-band equal Wilkinson power divider with the frequency ratio of 1.8 : 1 and an unequal one with the high power dividing ratio of 7 : 1 and frequency ratio of 1.8 : 1 are designed, fabricated and measured. The measurements are in good agreement with the simulations. It is shown that the proposed power dividers have simple topologies, and can be easily fabricated with small frequency ratios and high power dividing ratios.

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