Laser-induced graphene (LIG) is an emerging technique for producing few-layer graphene or graphene-like material that has recently received increasing attention, due to its unique advantages. Subsequently, a variety of lasers and materials have been used to fabricate LIG using this technique. However, there is a lack of understanding of how different lasers (wavelengths) perform differently in the LIG conversion process. In this study, the produced LIG on polyimide (PI) under a locally water-cooled condition using a 10.6 μm CO₂ infrared laser and a 355 nm ultraviolet (UV) laser are compared. The experimental investigations reveal that under the same UV and CO₂ laser fluence, the ablation of PI show different results. Surface morphologies with micron-sized and nanometer pores were formed by the UV laser under different laser fluences, whereas micron-sized pores and sheet structure with fewer pores were produced by the CO₂ laser. Energy dispersive spectrometry and three-dimensional topography characterization indicate that the photochemical effects were also involved in the LIG conversion with UV laser irradiation. It is also observed through experiments that the photothermal effect contributed to the formation of LIG under both lasers, and the LIG formed on PI substrates by the CO₂ laser showed better quality and fewer layers.

Navigation technology is an essential ability for the survival and development of animals and humans. We integrate a bilayer nanowire polarizer with a photodetector using nanoimprint lithography, and apply the integrated polarization dependent photodetector (PDP) as a polarization navigation sensor. The proposed device is designed to have the top sensitivity at the blue band. The integration process can fabricate nanowires with multiorientations simultaneously and eliminate the alignment error. The angle output experiment of the navigation sensor using the integrated device is investigated. The angle output error is within ±0.1^°. The results show that the fabricated PDP has good application prospects in the field of polarization navigation.

We report a method of integrating the single-layer nanowire polarizers with photodetectors, and the fabricated device is used as the polarization navigation sensor. The fabrication processes mainly based on nanoimprint lithography and dry etching. The fabrication method can fabricate nanogratings with multi-orientation simultaneously, so angular alignment error is eliminated. The external quantum efficiency of the integrated device is tested, and a peak external quantum efficiency of 23% at around 440 nm is achieved. The indoor angle output experiment of a navigation sensor is investigated, and the angle output error is tested to be within ±0.1°. The outdoor angle output experiment has also been tested, and the errors are less than ±1.5°. The measurement results show that the fabricated device is suitable for polarization navigation.

Multioriented bilayer nanowire polarizers are integrated with photodetectors using only one-time nanoimprint lithography and metal deposition process. In order to keep the position of peak external quantum efficiency of the photodetector unchanged, the bilayer nanowire polarizer is designed to have the highest transmission at 440 nm. The photodetector is integrated with the polarizer after surface treatment. The performance of the fabricated device is then tested, and three characteristics are realized: light-intensity sensitive, polarization sensitive, and blue-light sensitive. The proposed integration method simplified the fabrication process, and the fabricated device avoids the alignment error which would be produced by using discrete elements. The results demonstrate that the proposed integration process is a promising method for fabricating photodetectors with polarization function.