报告时间：8月11日  14:00

报告地点：光学楼525室

题目：Kagome Fibre: a new paradigm in pulse compression and beam delivery of ultra-high Power Ultra-Short Pulsed Lasers

Abstract:

In 2002 the development of a new type of hollow-core photonic crystal fibre (HC-PCF), coined Kagome fibre, has been reported [1]. The fibre guides light via a new mechanism that doesn’t require a photonic bandgap in the fibre cladding [2]. This guidance mechanism, called Inhibited Coupling (IC), is the guided photonic analogue of the concept of bound or quasi-bound state in a continuum established within the field of solid-state quantum physics. The IC guidance offered a design tool to the seminal introduction of hypocycloid core-contour (i.e. negative curvature) hollow-core photonic crystal fibre [3,4], which allowed a dramatic reduction in transmission loss of IC guiding HC-PCF [5,6,7]. This improvement is such that IC guiding HC-PCF, which previous typical loss figure was in the range of 0.5-1 dB/m, outperforms photonic bandgap (PBG) guiding HC-PCF in optical transmission. Today, the lowest loss figures at the benchmark wavelengths of the NIR-VIS spectral range are all set by the hypocycloid core-contour (HCC) kagome HC-PCF. The records are 17 dB/km ~1μm wavelength [5], 70dB/km at ~780 nm [6] and 70 dB/km at 500-600 nm wavelength range [7], and more recently, using IC guiding tubular lattice HC-PCF, we demonstrated a loss as low as 7.7 dB/km at 750 nm [13].

Furthermore, because of the intrinsic properties of the IC guidance, the reduction in loss means systematically a reduction in the power-overlap with the silica core-surround. As a result unprecedented handling of laser pulse-energy and optical power is demonstrated with ultra-low transmission loss. This has been illustrated in the recent results in ultra-short pulse transportation and compression [8-11,5], leading to the record 1 mJ energy pulse delivery [5]. Here, 1 milli-Joule energy, gigawatt peak power and close-to pettawatt/cm2 intensity ultra-fast laser-pulses from 600 fs Yb fiber-laser were successfully guided and compressed in HC-PCF. The guidance was achieved with low loss and in a single-mode fashion, and the pulse compression is achieved in a self-compression manner. Another result in high optical-field is the self-compression down to sub-cycle regime of 80 fs USP operating at 1.8 μm and with several tens of μJ pulse-energy [11]. These results open exciting prospects in fibre based high field photonics and laser micromachining. As a matter of fact, IC guiding Kagome HC-PCF is currently commercially available from GLOphotonics [12] and is strongly used as a fibre beam delivery of high power ultra-short pulse lasers.