Instead of inscribing the discrete phases into each local period of the seed HLPG, an equivalent approach to realize the phase-only sampled multichannel helical long-period fiber grating (HLPG) has been demonstrated both theoretically and experimentally which is realized by superposing the so-called sampling HLPGs with the seed HLPG in a same region of the fiber. The proposed approach can greatly facilitate the fabrication processes of the multichannel HLPG by using the direct CO ₂ laser writing technique, meanwhile it enables to provide much more design and fabrication flexibilities for high channel-count HLPG than the previous methods. As examples, a 3-channel and a 5-channel HLPG have been successfully demonstrated. Moreover, the orbital angular momentum (OAM) modes inherently existed at all channels of the fabricated HLPG have also been verified, which highlights that the proposed HLPGs could find application to multi-wavelength OAM mode converter as well.

Lately, ceramic fuel cells (CFCs) have held exceptional promise for joint small- and large-scale applications. However, the low-oxygen reduction response of cathode materials has hindered the low operating temperature of CFCs. Herein, we have developed a semiconductor based on La and Ce co-doped SrCoO₃ and embedded them in porous Ni-foam to study their electrochemical properties. The porous Ni-foam-pasted La_0.2Sr_0.8Co_0.8Ce_0.2O_3‒δ cathode displays small-area-specific resistance and excellent ORR (oxygen reduction reaction) activity at low operating temperatures (LT) of 450–500 °C. The proposed device has delivered an impressive fuel cell performance of 440 mW-cm⁻², using La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam substrate cathode operation at 550 °C with H₂ fuel and atmospheric air. It even can function well at a lower temperature of 450 °C. Moreover, La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam shows very good activation energy compared to individual SrCoO₃ and La_0.1Sr_0.9Co_0.9Ce_0.1O_3−δ embedded on porous Ni-foam, which help to promote ORR activity. Different characterization has been deployed, likewise: X-ray diffraction, photoelectron-spectroscopy, and electrochemical impedance spectroscopy for a better understanding of improved ORR electrocatalytic activity of prepared La_0.2Sr_0.8Co_0.8Ce_0.2O_3−δ embedded on porous Ni-foam substrate. These results can further help to develop functional cobalt-free electrocatalysts for LT-SOFCs.

The challenging research topic for developing low-temperature ceramic fuel cells (LT-CFCs) is to design electrolytes with sufficient ionic conductivity either via doping or composite semiconductors with ionic conductors. Following this challenging topic, we have developed and synthesized a novel semiconductor ionic heterostructure La_0.8Sr_0.2Co_0.8Fe_0.2O₃-Gd_0.1Ce_0.9O₂ (LSCF-GDC) with different compositions and deployed it as an electrolyte to realize the functionality of the fuel cell. The developed LSCF-GDC electrolyte with mixed conduction of ions and protons possesses high ionic conductivity with only 0.06 Ohm·cm² of ohmic area-specific resistance for the electrolyte component. The fuel cell using 3LSCF-7GDC as the electrolyte exhibits the best fuel cell performance of 1060 mW·cm⁻² and an open circuit voltage (OCV) of 1.11 V at a low operating temperature of 550 °C among individual GDC, LSCF, and different heterostructures of LSCF and GDC. The attained performance and ionic conductivity are specially accredited to constructing heterostructures and massively deficient structures at the interface of the LSCF and GDC. The advanced semiconductor ionic heterostructure of LSCF-GDC provides new insight into designing new electrolytes with high ionic conductivity for LT-CFC applications.