Porous Fe3O4/Fe/SiO2 core/shell nanorods were fabricated, in which the diameter of the pores was 5–30 nm. The magnetic and electromagnetic properties were investigated. The temperature dependent magnetic measurements showed that these nanorods were ferromagnetic with a Verwey temperature of 129 K. The electromagnetic data indicated that effective complementarities between the dielectric loss and the magnetic loss were realized, suggesting that they have excellent electromagnetic wave absorption properties. Thus the porous core/shell nanorods could be used as a kind of candidate absorber.
We report on 980-nm InGaAs/GaAs lasers with dual-lobed far field based on a single-sided Bragg reflection waveguide (BRW). The high slope efficiency ∼0.92 W/A and a continuous wave (CW) output power >1.5 W (3.2 W pulsed) have been obtained. The threshold current density is as low as 253 A/cm 2 for a 1.5-mm-long device and the transparency current density is only 140 A/cm 2 . The further analysis shows the intrinsic reason for the single-lobed or the dual-lobed far-field distribution is determined by the mode shape in the cavity, not the single-sided or dual-sided BRW structure. The condition to achieve a narrow singlelobed far-field distribution is discussed.
As a novel portable and robust broadband coherent light source, mid-infrared (MIR) Kerr microresonator-based frequency combs (microcombs) have prospective applications in the precision spectroscopy of molecules and biochemical sensing. The mature integrated silicon photonics platform is well suited for the MIR microcombs study because silicon has both large linear and nonlinear refractive index, but the transparency window of the platform is limited by the cladding material. Here, we numerically demonstrate the generation of a broadband MIR comb in a silicon microring resonator, harnessing the large-cross-section air-cladding waveguide to alleviate the absorption loss. The effects of higher order nonlinearities are also investigated, which show that the effect of five-photon absorption around the pump wavelength (4.78 µm) is negligible while an octave-spanning (3.5-8 µm) Raman-Kerr comb line can be obtained with the assistance of Raman effect and a quite pure Kerr frequency soliton comb can also be achieved at large detuning. The proposed structure can be compatible with the CMOS technology, thus can be a very promising solution to the MIR integrated photonics.
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