This paper reports that, based on the electromagnetic scattering theory of the multipole method, a high-quality hollow beam is produced through a selectively liquid-filled photonic crystal fibre. Instead of a doughnut shape, a typical hollow beam is produced by other methods; the mode-field images of the hollow-beam photonic crystal fibre satisfy sixth-order rotation symmetry, according to the symmetry of the photonic crystal fibre (PCF) structure. A dark spot size of the liquid-filled photonic crystal fibre-generated hollow beam can be tuned by inserting liquid into the cladding region and varying the photonic crystal fibre structure parameters. The liquid-filled PCF makes a convenient and flexible tool for the guiding and trapping of atoms and the creation of all-fibre optical tweezers.

http://iopscience.iop.org/article/10.1088/1674-1056/19/4/047103/pdf

A dark hollow beam from a selectively liquid-filled photonic crystal fibre

Kinds of photonic crystal fibers with chalcogenide core tellurite cladding composite microstructure are proposed. The multi-core photonic crystal fiber can reach the higher nonlinearity coefficient and the larger effective mode area. The small single-core photonic crystal fiber has a very high nonlinearity coefficient. At the wavelength λ = 0.8 μm, the nonlinearity coefficient can reach 31.37053 W−1m−1, at the wavelength λ = 1.55 μm, the nonlinearity coefficient is 11.19686 W−1m−1.

https://iopscience.iop.org/article/10.1088/1674-1056/22/7/074206/pdf

Numerical analysis of photonic crystal fiber with chalcogenide core tellurite cladding composite microstructure

A kind of improved high birefringence photonic crystal fibre (PCF) is proposed in this paper. The characteristics of birefringence, dispersion and leakage loss are studied by the multipole method. Numerical results show that the improved PCF possesses the properties of a flat dispersion and single mode operation. Moreover, with the operating wavelength λ = 1.55 μm, the modal birefringence increases greatly in comparison with that of the original PCF, and the leakage loss is about 104 times smaller than that of the original PCF because the modification gives rise to the strong confinement of guided modes. It is expected that the improved PCF can be used as high birefringence and dispersion flattened fibres.

Improved high birefringence photonic crystal fibres with dispersion flattened and single mode operation

We demonstrate a strictly all-polarization maintaining, all-fiber chirped pulse amplification of ultrashort pulses. Pulses with the duration of 933 fs and energy as high as 50 μJ are achieved at 200 kHz repetition rate in a compact size. The variations of the spectra and pulse widths as functions of the amplified output power have also been presented. To our best knowledge, this is the highest energy extracted from the strictly all-fiber chirped pulse amplification system. The environmentally stable femtosecond laser source will find various applications in practice.

50 μJ Femtosecond Laser System Based on Strictly All-Fiber CPA Structure

Numerical simulation for optimizing mode shaping and supercontinuum flatness of liquid filled seven-core photonic crystal fibers

The eigenvalue equation associated with seven-core photonic crystal fiber was derived from coupled-mode equation. Mode properties were analyzed by its eigenvalues and eigenvector. Using the frequency domain finite difference method, the relationship between fiber structure and coupling coefficient was fully discussed through changing the wavelength, hole pitch and core distance. Mode shaping and higher-order supermode cut off was realized. The results were helpful to the fiber structure design and in-phase supermode selection.

Numerical analysis for structure optimization of seven-core photonic crystal fibers

Hundreds of Megawatts Peak Power Multi-Core Photonic Crystal Fiber Laser Amplifier

A mode locked fiber laser based on Yb-doped large mode area photonic crystal fiber operating in the all-normal dispersion regime is experimentally studied. The eighteen cores of the gain fiber are arranged in array-type geometry with an equivalent mode diameter of about 52 μm. A sigma laser cavity is used without using any elements for dispersion compensation. Reliable self-starting mode-locking is achieved using a fast semiconductor saturable absorber mirror. The laser directly produces 4.92 ps chirped pulses at a 44.68 MHz repetition rate for an average power of 3.3 W corresponding to a pulse energy of 74 nJ. The pulses are compressed to 780 fs with a grating pair outside the cavity.

Fang Xiao-Hui

Papers

Numerical analysis for structure optimization of seven-core photonic crystal fibers

Hundreds of Megawatts Peak Power Multi-Core Photonic Crystal Fiber Laser Amplifier

Mode locked multi-core photonic crystal fiber laser