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We investigated an all-optical phase shifter and switch based on a graphene decorated side-polished twin-core fiber (TCF) Michelson interferometer (MI). The MI was fabricated by tapering the splicing point between the TCF and single-mode fiber. The flat surface of exposed polished core in the TCF was coated with monolayer graphene. A 980 nm pump laser is used to produce a photothermal effect. The graphene’s ohmic heating changes the effective refractive index of the exposed core, resulting in the phase shift of the MI. The MI with a polished length of 5 mm has a significant modulation phase shift with a nearly linear slope of 0.0102 π / m W near the wavelength of 1550 nm and can obtain an extinction ratio of 7 dB for optical switching with a rise (fall) time of 55.8 ms (15.5 ms). The high-density integration and all-optical control enable the proposed device to have great potential in the miniaturization of optical devices and all-optical signal processing.

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Laser powder bed fusion is an attractive manufacturing technology promising novel components for the aircraft, automobile, and medical industries. However, depending on the material, some defects in the parts, especially pores or microcracks, cannot be avoided in the LPBF process. To achieve a part with low defect density, the optimal parameter sets must be determined. Many investigations have focused on how laser speed and laser power influence the melting process and the relative density of as-built parts. In this study, we considered laser and heated powder beds as two energy input sources, represented by volume energy density and preheating temperature, respectively. The interaction of these two energy inputs for the fabrication of AISI H13 was investigated. It was found that high preheating temperatures shifted the optimal parameter sets from the low energy density area to the high energy density area. In addition, high preheating also led to hot cracking, which was confirmed with Scheil solidification simulations.

We propose and investigate an all-fiber thermo-optic modulator based on a side-polished twin-core fiber (TCF) Michelson interferometer (MI) coated with NaNdF4 nanoparticles. The MI was fabricated by tapering the splicing point between the TCF and a single mode fiber (SMF). A short suspended core fiber (SCF) is spliced to one core of the TCF to introduce a fixed optical phase difference (OPD). The side-polished core is coated with photo-thermal material NaNdF4. Owing to the ohmic heating of NaNdF4 nanoparticles under 808 nm pump laser, the effective refractive index of the polished core is changed, resulting in a phase shift of the MI. The MI has a significant modulation phase shift with 2.9 π near the wavelength of 1260 nm and can obtain an optical switching with a rise (fall) time of 152 (50) ms. The proposed device will have a great application potential in optical modulators due to compact structure and strong robustness.