Frequency-Tunable Pulsed Microwave Waveform Generation Based on Unbalanced Single-Arm Interferometer Excited by Near-Infrared Femtosecond Laser

Femtosecond laser-excited generation of frequency-tunable microwave pulses, based on an unbalanced single-arm interferometer with frequency-to-time mapping, has been proposed and demonstrated with easy-to-obtain commercial devices. The optical wave-to-microwave frequency conversion, which involves continuous tuning in the range from 2.0 GHz to 19.7 GHz, was achieved based on simple spatial–optical group delay adjustment. Additionally, the pulse duration of the microwave waveform was measured to be 24 ns as the length of the linear dispersion optical fiber was fixed at 20 km. In addition, owing to the designs of the single-arm optical path and polarization-independent interference, the generated microwave pulse train had better stability in terms of frequency and electrical amplitude. Furthermore, a near-triangular-shaped microwave pulse at 4.5 GHz was experimentally obtained by the superposition of two generated sinusoidal signals, which verified the potential of this system to synthesize special microwave waveform pulses.

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Antireflective and Superhydrophilic Structure on Graphite Written by Femtosecond Laser

Micromachines ◽

10.3390/mi12030236 ◽

2021 ◽

Vol 12 (3) ◽

pp. 236

Author(s):

Rui Lou ◽

Guangying Li ◽

Xu Wang ◽

Wenfu Zhang ◽

Yishan Wang ◽

...

Keyword(s):

Femtosecond Laser ◽

Near Infrared ◽

High Efficiency ◽

Electronic Devices ◽

Sample Surface ◽

Graphite Surface ◽

Hazardous Substances ◽

Functional Surface ◽

Nano Structures ◽

Average Reflectance

Antireflection and superhydrophilicity performance are desirable for improving the properties of electronic devices. Here, we experimentally provide a strategy of femtosecond laser preparation to create micro-nanostructures on the graphite surface in an air environment. The modified graphite surface is covered with abundant micro-nano structures, and its average reflectance is measured to be 2.7% in the ultraviolet, visible and near-infrared regions (250 to 2250 nm). The wettability transformation of the surface from hydrophilicity to superhydrophilicity is realized. Besides, graphene oxide (GO) and graphene are proved to be formed on the sample surface. This micro-nanostructuring method, which demonstrates features of high efficiency, high controllability, and hazardous substances zero discharge, exhibits the application for functional surface.

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Regulating disordered plasmonic nanoparticles into polarization sensitive metasurfaces

Nanophotonics ◽

10.1515/nanoph-2020-0651 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Shulei Li ◽

Mingcheng Panmai ◽

Shaolong Tie ◽

Yi Xu ◽

Jin Xiang ◽

...

Keyword(s):

Femtosecond Laser ◽

Spatial Resolution ◽

Metallic Nanoparticles ◽

Near Infrared ◽

Optical Memory ◽

Laser Pulses ◽

Femtosecond Laser Pulses ◽

Optical Diffraction ◽

Plasmonic Nanoparticles ◽

Direct Laser

Abstract Metasurfaces composed of regularly arranged and deliberately oriented metallic nanoparticles can be employed to manipulate the amplitude, phase and polarization of an incident electromagnetic wave. The metasurfaces operating in the visible to near infrared spectral range rely on the modern fabrication technologies which offer a spatial resolution beyond the optical diffraction limit. Although direct laser writing is an alternative to the fabrication of nanostructures, the achievement of regular nanostructures with deep-subwavelength periods by using this method remains a big challenge. Here, we proposed and demonstrated a novel strategy for regulating disordered plasmonic nanoparticles into nanogratings with deep-subwavelength periods and reshaped nanoparticles by using femtosecond laser pulses. The orientations of the nanogratings depend strongly on the polarization of the femtosecond laser light. Such nanogratings exhibit reflection and polarization control over the reflected light, enabling the realization of polarization sensitive optical memory and color display with high spatial resolution and good chromacity.

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