Ultra low-loss hypocycloid-core Kagome hollow-core photonic crystal fiber for green spectral-range applications

Abstract

We report on the development of a hypocycloidal-core Kagome hollow-core photonic crystal fiber guiding, with low transmission loss in the 450-650 nm visible spectral range. Transmission loss records have been achieved with 70 dB/km at 600 nm, and 130 dB/km at 532 nm. As a demonstration of the fiber potential applications, we report on a compact 600 THz wide Raman comb generator, centered around 532 nm, and on a 10 W average power frequency-doubled Yb-fiber picosecond laser beam delivery, along with its use for organic material laser micro-processing.

Semi-analytical model for hollow-core anti-resonant fibers

“…Actually, the hollow-core anti-resonant fiber (HC-ARF) and its leaky core mode have been investigated for decades [14][15][16]. However, only in recent years, the introduction of hypocycloid [17] or negative curvature [18] core-surround structures revived the development of HC-ARF since it enables coexistence of broadband light confinement (200-800 THz) and low transmission attenuation (20-100 dB/km depending on the wavelength) [19,20]. Furthermore, the spatial overlap of the core mode with the glass material is universally one order of magnitude smaller in HC-ARF than in HC-PBGF [21].…”

Optimized inhibited-coupling Kagome fibers at Yb-Nd:Yag (85 dB/km) and Ti:Sa (30 dB/km) ranges

“…The introduction of hypocycloid core contour was a direct consequence of the IC mechanism where the fiber-core guidance is based on strongly reducing the optical overlap between the guided core mode and the continuum cladding modes. This in turn explains the loss reduction from a decibel per meter (dB/m) level in the first IC guiding HC-PCF, which took the form of a Kagome lattice cladding surrounding a hollow core with a circular [1] or a hexagonal core contour [2], to a tens of dB/km level in hypocycloid core-contour HC-PCF [3,5,11,16,17]. The impact of the corecontour geometry on the fiber confinement loss (CL) was detailed in [5], where it was shown that the larger the negative curvature of the core-contour cups, the lower the CL and fraction of the power overlap one can reach.…”

“…The suitability of such fiber technology for USP lasers has been illustrated, for example, in the transport of 600-fs pulses at the millijoule energy level in robustly single-mode fashion using a 10-m-long piece of this IC Kagome HC-PCF [8]. Furthermore, this power and energy handling has been demonstrated with the most commonly used USP lasers, such as those based on Yb or Nd:Yag [8,9], on Ti:Sapphire (Ti:Saph) [10], or on frequency-doubled Yb [11] or Er [12]. Finally, any improvement in the transmission performance of these fibers will further improve the growing and spreading use of USP lasers in industrial applications as various as biophotonics [13], micro-machining [14] and micro-surgery [15].…”

“…Since then, much progress has been made in both understanding the entailed guidance mechanism [2] and in its transmission performance. The latter has been continuously improved since the introduction of hypocycloid core contour (i.e., negative curvature core contour) in 2010, which led, within a short period of time, to several and successive record loss figures in the visible/ near-infrared [3,5,11,16,17]. The most recent one reported presents a loss figure of 7.7 dB/km at 750 nm using tubular amorphous lattice HC-PCF [7].…”

Splicing tapered inhibited-coupling hypocycloid-core Kagome fiber to SMF fibers

“…negative curvature) to hollow fibers [2], which allowed a dramatic drop in the transmission loss. Today, IC guiding hypocycloid-core Kagome HC-PCF outperforms their photonic bandgap (PBG) guiding counterparts in the NIR-VIS spectral range with record loss figures of 17 dB/km at ~1 µm wavelength range [3], 70 dB/km at ~780 nm [4] and 70 dB/km at 500-600 nm wavelength range [5]. Furthermore, even with a single ring cladding design [6], transmission loss of ~30 dB/km around 3-4 µm wavelength range were reported [7].…”