Multimode (MM) laser light has a vast application history spanning from laser pump sources, to high-speed optical links, to imaging systems but can suffer enormous inefficiencies when coupled through a solid core optical fiber for long transmission path lengths. One way to improve the MM transmission is by replacing the traditional solid-core fibers with uniquely tailored nested antiresonant hollow-core fibers (NANFs). By improving upon previous design methods, one can extend the application of the HCF to 100s of modes and beyond while maintaining low loss thus enabling novel concepts such as power beaming through fiber and the transmission of spatiotemporal tailored ultrafast wavepackets. We report a uniquely designed, fabricated, and tested MM NANF that enables low-loss transmission of 100s of modes.
This paper aims to improve the post-fabrication transmission performance of nested hollow-core fibers (HCF) by incorporating random perturbations inside the cladding structure in the fiber model and evaluating their impact on the overall guidance performance by applying a Monte-Carlo simulation strategy. Varying silicawall thicknesses, asymmetric misalignments of the nested and surrounding cladding elements, and anisotropic deformations are investigated and result in loss increases up to 2%, 6%, and 62%, respectively, for fundamental mode propagation at 1.55 μm. Higher-order modes are affected over one magnitude stronger, although the impact is highly wavelength-dependent, switching dominating effect and mode susceptibility dynamically.
We will present our recent work using noble and Raman-active gas-filled anti-resonant hollow-core fiber (ARHCF) technology. First, we will present the generation of supercontinuum spanning from 200 nm to 4000 nm based on nonlinear effects of soliton self-compression and phase-matched deep‑ultraviolet (DUV) dispersive wave (DW) emission in Argon (Ar)-filled ARHCFs pumped at 2.46 μm wavelength with 100 fs pulses and ~8μJ pulse energy. Then we will discuss our recent work on stimulated Raman scattering (SRS) effect in a hydrogen (H2)-filled ARHCF, to achieve near- and MIR Raman lasers. By employing the single-stage vibrational SRS effect, a 4.22 μm Raman laser line is directly converted from a linearly polarized 1.53 μm pump laser. A quantum efficiency as high as 74% was achieved, to yield 17.6 µJ pulse energy. The designed 4.22 μm wavelength is well overlapped with the strongest CO2 absorption, therefore constituting a promising way for CO2 detection. In addition, we report a multi-wavelength Raman laser based on the cascaded rotational SRS effect. Four Raman lines at 1683 nm, 1868 nm, 2100 nm, and 2400 nm are generated, with pulse energies as high as 18.25 µJ, 14.4 µJ, 14.1 µJ, and 8.2 µJ, respectively. The energy of these Raman lines can be controlled by tuning the H2 pressure from 1 bar to 20 bar.
The key advantages of ultrafast fiber lasers compared to their bulk competitors are their small footprints, low costs and nearly diffraction limited beam quality. The pulse energy of fiber based ultrafast oscillators is still inferior comparted to ultrafast bulk oscillators. In the last decade substantial effort has been devoted to overcome this hurdle, including the development of novel saturable absorber schemes. In this work, we discuss the pulse energy scaling potential of all normal dispersion (ANDI) fiber lasers utilizing Ytterbium doped multicore fiber as saturable absorber.
Detection of ammonia based on an all-fiber configuration is reported. The system consists of a hollowcore photonic-bandgap (HC-PBG) fiber with 20μm core diameter and transmission window from 1490 to 1680 nm. Absorption bands of ammonia at ~1538 nm are targeted using a supercontinuum source with central wavelength at 1550 nm. We present the method of achieving a complete fiber system while addressing the gas entry/exit path through the HC-PBG. Analysis of the ammonia absorbance in the fiber with respect to fiber length and response time is investigated. By operating in the near infrared, we demonstrate how the proposed system addresses several challenges associated with fiber-based gas-sensing, using readily available commercial components.
We present a residual dispersion compensating highly birefringent photonic crystal fiber (PCF) based on an octagonal structure for broadband dispersion compensation in the wavelength range 1460–1625 nm. The finite element method with perfectly matched boundary condition is used as the numerical design tool. It has been shown theoretically that it is possible to obtain a negative dispersion coefficient of about −418 to −775 ps/nm/km over the S-, C-, and L-bands, relative dispersion slope (RDS) close to that of single mode fiber (SMF) of about 0.0036 nm −1 at 1550 nm. According to the simulation, birefringence of 2×10 −2 is obtained at 1550-nm wavelength. The variation of structural parameters is also studied to evaluate the tolerance of the fabrication. The proposed octagonal PCF can be a potential candidate for residual dispersion compensation as well as maintaining single polarization in optical fiber transmission system.
A photonic crystal fiber design is presented, which has simultaneously ultra-high birefringence, high nonlinearity, and high negative dispersion. The relative dispersion slope matches with that of standard single-mode fiber of about 0.0036 nm −1 . The finite element method with circular perfectly matched boundary layer is used to investigate the guiding properties. The proposed fiber ensures a large negative dispersion coefficient of about −639.16 ps/(nm km) , birefringence of order 3.55×10 −2 , and nonlinear coefficient of 41 W −1 km −1 at 1550-nm wavelength.
A highly birefringent dispersion compensating microstructure optical fiber (MOF) based on a modified spiral (MS)-MOF is presented that successfully compensates the dispersion covering the E- to L-communication bands ranging from 1370 to 1640 nm. It is shown theoretically that it can obtain a negative dispersion coefficient of about −221 to −424 ps/(nm⋅km) ) over S to L bands and −327 ps/(nm⋅ km) ) at the operating wavelength of 1550 nm. The relative dispersion slope is perfectly matched to that of single-mode fiber of about 0.0036 nm −1 . Besides, the proposed MS-MOF offers high birefringence of 1.79×10 −2 with a large nonlinear coefficient of about 41.8 W −1 km −1 at the operating wavelength along with two zero dispersion wavelengths at 610 and 1220 nm. Futhermore, the variation of structural parameters is also studied to evaluate the tolerance of the fabrication.
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