Hollow-Core Photonic Crystal Fiber (HCPCF) technology has revolutionized Ultra-Short Pulse (USP) laser beam delivery. Industry-grade USP laser beam delivery system (BDS) modules, developed by GLOphotonics, however, display polarization fluctuations during movement. To overcome this, we've developed a BDS module maintaining constant polarization irrespective of motion. This BDS uses an inhibited-coupling HCPCF with an injected beam from a 1030 nm wavelength USP laser. Demonstrating a 97% transmission rate and stable linear polarization (34dB of polarization extinction ratio (PER)), it showed less than 3% power fluctuation and less than 1% polarization fluctuation during movement. This marks a significant advancement in BDS applications.
We report the first, to our knowledge, linear HCPCF-bundle for USP laser beam-delivery, power-modulation, and spatial-shaping. This bundle comprises four identical inhibited coupling HCPCFs arranged in a linear array with a relative pitch-variation of less than 2% relative variation in array pitch. Each HCPCF is equipped with an acousto-optic modulator (AOM) for independent power modulation. A laser beam, from 1030 nm wavelength, 100μJ energy USP laser, is split into four beams and coupled to each of the HCPCFs in the bundle using a diffractive optic element. The system's insertion loss (from input to output through the AOM) is measured to be over 70%. The bundle system emits an array of four Gaussian beams, each with equal energy and beam size (both having less than 1% variation beam to beam). Each beam's power can be modulated independently. This development marks a significant advancement in harnessing HCPCF technology in applications requiring high-power light with spatial and temporal structuring.
Micro processing applications using femtosecond lasers have developed thanks to the quality of the process. A challenge still to be addressed is the capability to deliver the beam through a fibre. One solution is the use of hollow-core inhibited coupling fibres, nevertheless its use requires a beam stabilization to insure a stable operation.
This study attempts to qualify two beam stabilisation systems: two piezo motors coupled with four quadrant detectors and Cailabs’ all-optical mode-cleaner system based Multi-Plane Light Conversion (MPLC) technology. To do such output fibre transmission efficiency and beam quality are investigated under controlled fluctuation of beam pointing.
A beam delivery system (BDS) fibered with hollow core photonic crystal fibre (HC-PCF) has been identified as very promising for ultra-short pulse (USP) laser micromachining for it allows flexible, secured and robust laser beam delivery to the work piece. These features are of paramount importance for vertical markets such as automotive or consumer electronics. We report on a system that integrates a BDS, a laser beam pointing stabilization module and a 50 W power, 250 fs pulsewidth Yb-based USP laser. The BDS comprises a low loss, low dispersion and high damage threshold Inhibited-Coupling (IC) HC-PCF. The latter is ruggedized with a semi-rigid industrial cable with ends attached respectively to an injection head for ease of laser beam coupling, and to an output connector for beam delivery to the work piece. The injection head is aligned with a special module for laser beam jitter stabilization and beam-shape control and monitoring. Also, it exhibits the necessary gas and thermal handling to minimize parasitic optical nonlinear effect or photoionization and power induced heating. To test the endurance of this fibered-USP laser system, it was continuously run over 17 hours. The results show exceptional integrity in the power transmission (86 ±1%), spectral and temporal structure and beam quality (M2~1.1). The BDS output beam shows a pointing stability of only 0.7±0.1 μrad. These results represent an important milestone towards the industrialization of fiber delivered USP laser-based machines.
We report on several ultra-short pulse compression schemes based on hollow-core photonic crystal fiber filled with a chosen gas-phase medium and undertaken in a versatile module coined “FastLas”. The scheme relies on dispersion management by both fiber design and gas pressure management to offer a highly versatile pulse compressor. Furthermore, the gas is also used to set the required optical nonlinearity. This type of hollow fiber based compressor is scalable with the laser wavelength, pulse energy and initial pulse-width. Among the achieved pulse compression, we list a self-compression of 500-600 fs ultra-short pulse Yb-laser and with energy range of 10-500 μJ. By simply scaling the fiber length we demonstrated pulses as short as ~20 fs for the whole energy range. Here, the self-compression is achieved through solitonic dynamic. Conversely, we demonstrated pulse compression based on self-phase modulation by adjusting the fiber and gas dispersion. Among the pulse compressors we have developed, based on self-phase modulation, we cite the compression of a frequency-tripled micro-Joule pulse-energy Yb-laser with a pulse width of 250 fs. The results show compressed UVpulses with temporal width in the range of 50-60 fs.
KEYWORDS: Pulsed laser operation, Beam delivery, Fiber lasers, Head, Cladding, Near field, High power lasers, Near field optics, Photonic crystal fibers, Laser systems engineering
We report on an ultra-low loss Hollow-Core Photonic Crystal Fiber (HC-PCF) beam delivery system (GLO-GreenBDS) for high power ultra-short pulse lasers operating in the green spectral range (including 515 nm and 532 nm). The GLOBDS- Green combines ease-of-use, high laser-coupling efficiency, robustness and industrial compatible cabling. It comprises a pre-aligned laser-injection head, a sheath-cable protected HC-PCF and a modular fiber-output head. It enables fiber-core gas loading and evacuation in a hermetic fashion. A 5 m long GLO-BDS were demonstrated for a green short pulse laser with a transmission coefficient larger than 80%, and a laser output profile close to single-mode (M2 <1.3).
Raman-gas filled HC-PCF has proved to be an outstanding Raman-convertor, as illustrated by the generation of more than 5 octaves wide Raman comb using a hydrogen-filled Kagome HC-PCF pumped with high power picosecond-laser, or the generation of multiline Raman-source in the UV-Vis using a very compact system pumped with micro-chip laser. Whilst these demonstrations are promising, a principal challenge for the industrialization of such a Raman source is its lifetime as the H2 diffusion through silica is high enough to leak out from the fiber within only a few months. Here, we report on a HC-PCF based Raman multiline source with a very long life-span. The system consists of hydrogen filled ultra-low loss HC-PCF contained in highly sealed box, coined CombBox, and pumped with a 532 nm micro-chip laser. This combination is a turnkey multiline Raman-source with a "shoe box" size. The CombBox is a robust and compact component that can be integrated and pumped with any common pulsed laser. When pumped with a 32 mW average power and 1 ns frequency-doubled Nd:Yag microchip laser, this Raman-source generates 24 lines spanning from 355 to 745 nm, and a peak power density per line of 260 mW/nm for the strongest lines. Both the output power and the spectrum remained constant over its monitoring duration of more than six months. The spectrum of this multiline laser superimposes with no less than 17 absorption peaks of fluorescent dyes from the Alexa Fluor family used as biological markers.
We report on high power Raman-converter frequency stage based on hydrogen-filled inhibited-coupling hollow-core photonic crystal fibers pumped by an Yb-fiber picosecond laser. This fiber Raman-convertor can operate in two SRS emission regimes by simply controlling the fiber length or the gas pressure. It can set to either generate favorably single laser line or to generate an extremely wide Raman comb. Based on this we demonstrate a pico-second pulse Raman source of 9.3 W average-power at 1.8 μm, and an ultra-wide Raman comb spanning over more than five octaves from UV to mid-infrared, containing around 70 laser lines.
The dramatic progress in power-scaling of ultra-short pulse (USP) lasers and their growing use in industrial applications call for flexible and robust beam delivery systems (BDS) over several meters with no temporal or modal distortions. Inhibited coupling (IC) hypocycloid Kagome hollow-core photonic crystal fiber (HC-PCF) has recently proved to be an excellent solution for guiding these USP. In order to reduce further the attenuation of such fiber and then to increase the BDS capabilities, we report on an optimized IC Kagome HC-PCF exhibiting record loss level (8.5dB/km at 1030nm) associated with a 225nm wide 3-dB bandwidth and low bend sensitivity.
We report on a Hollow Core-Photonic Crystal Fiber (HC-PCF) based high power ultra-short pulse laser beam delivery system (GLO-BDS) that combines ease-of-use, high laser-coupling efficiency, robustness and industrial compatible cabling. The GLO-BDS comprises a pre-aligned laser-injection head, a sheath cable protected HC-PCF and a modular fiber-output head. It enables fiber-core gas loading and evacuation in a hermetic fashion. 5 m long GLO-BDS were demonstrated for Yb USP laser, Ti:Sapphire laser and frequency-doubled Yb USP laser. They all exhibit a transmission coefficient larger than 80%, and a laser output profile close to single mode (M2 <1.3).
We report on the fiber-based transmission of sub-ps single-mode pulses with an average power of 50 W at a wavelength of 1030 nm generated by a TruMicro Series 5000 Femto Edition thin disk amplifier. The air-filled hollow-core Kagométype delivery fiber exhibits a hypocycloid core wall and is tailored to offer very low dispersion and nonlinearity at 1030 nm. It minimizes the mode overlap with the glass components to obtain a sufficiently high damage threshold. With propagation losses of only 20 dB/km and an optimized mode matching and coupling by means of a telescope and a 5- axes table we achieve an overall transmission efficiency of more than 80% with a resulting M2 of 1.15. Our laser source offers the selection of repetition rates from 200 to 800 kHz which translates to pulse energies between 60 and 250 μJ. The pulse duration of 900 fs is maintained at the fiber exit, while the spectral width broadens to 20 nm due to self phase modulation in the air core, which could be used to further compress the pulses temporally. Using a fiber-based beam transport allows for mechanical decoupling of the processing head from the laser source, increasing flexibility for applications in the field of material processing with ultra-short pulsed lasers.
Hollow-core microstructured fibres are designed for the short wavelength domains, either visible or ultra-violet
ones. The experimental results confirm that kagomé-lattice antiresonant fibres are good candidate for this
purpose. Thorough numerical modelling is carried out in order to determine the physical causes responsible for
the loss level observed. From these computations the following conclusions are drawn: (i) the sole antiresonant
core surround dictates the location of the transmission windows and (ii) the cladding bridges are sources of extra
leakage from the core to the surrounding solid cladding. A straightforward model is therefore devised to
determine accurately the loss level in this kind of structure by quasi-analytical calculus.
Optical fiber sources have experienced a massive growth over the past ten years principally due to the compactness,
robustness and good spatial quality of such systems. Fiber sources now cover a large spectrum from visible to near
infrared helped on this point by the development of microstructured fibers (MOFs). A particular class of MOFs also
called hollow-core photonic crystal fibers (HC-PCFs) offers to get rid of silica's absorption thanks to band gap guidance
and therefore to extend transmission range of silica fibers. We propose here two all-fiber architectures based on HCPCFs
in view to generate mid infrared wavelengths by amplification of spontaneous Raman scattering (SRS) in gaseous
medium. We report on design, fabrication and characterization of two kinds of HC-PCF matching the architecture needs.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.