研究目的
Investigating the development of plane-by-plane fiber Bragg gratings (FBGs) using a single pulse and a slit beam shaping technique to achieve enhanced optical properties.
研究成果
The slit beam shaping technique enables the inscription of high-quality plane-by-plane FBGs with uniform refractive index changes, lower transmission losses, and better reflectivity and FWHM compared to point-by-point FBGs. The method offers precise control over the grating's optical properties and demonstrates reduced polarization dependence.
研究不足
The energy efficiency decreases with the use of a slit, requiring higher pulse energies for smaller slit widths. The method's simplicity and control come at the cost of reduced efficiency compared to other beam shaping techniques.
1：Experimental Design and Method Selection:
The study employs a slit beam shaping technique to modify the focal volume of a femtosecond laser for inscribing FBGs. The relationship between the laser beam diameter and slit width is analytically modeled to achieve a circular cross-section.
2：Sample Selection and Data Sources:
FBGs are inscribed in the core of an SMF-28 fiber. The study uses a commercial femtosecond Fiber Laser Chirp Pulse Amplifier (FLCPA) operating at 1030 nm.
3：List of Experimental Equipment and Materials:
Includes a femtosecond laser, adjustable slit, objective lens, nanoresolution XYZ motor stage, and optical spectrum analyzer.
4：Experimental Procedures and Operational Workflow:
The laser pulses pass through an iris diaphragm and an adjustable slit before being focused onto the fiber core. The fiber is positioned on a slide with index-matching oil to avoid aberrations.
5：Data Analysis Methods:
The inscribed FBGs are characterized using quantitative phase microscopy (QPM) to analyze phase changes and width of modifications. Transmission and reflection spectra are measured to evaluate optical properties.
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