We experimentally and numerically demonstrate a simple and general technique to reduce the noise of modulational instability and soliton-based broadband supercontinuum lasers at the pulse-to-pulse level. Because of the requirement of low cost and high average power, such supercontinuum lasers constitute 99% of today’s commercially available supercontinuum lasers. The technique relies on adding a short normal dispersion fiber to force the spectrally and temporally distributed solitons to spectrally broaden through self-phase modulation (SPM) and thereby overlap to average out the noise. We experimentally demonstrate that this SPM technique provides significant noise reduction over a broad bandwidth.
Gas-filled hollow core fibers are a promising and unique platform for generation of ultrafast and wavelength tunable UV light. We present recent advances from our lab focused towards two vastly different industrial applications: Laser processing of solar cells and scatterometry. For processing of solar cells, we use the intrinsic wavelength tuning ability to investigate the potential for selective ablation and wire bonding. For scatterometry, which requires a broadband, flat, and low noise spectrum, we use pump modulation to create a pseudo-supercontinuum.
A broad and flat spectrum is preferable in many applications of supercontinuum sources. However, supercontinuum generation based on modulational instability often exhibits a prominent narrow blue peak followed by a significant dip in the neighboring longer-wavelength region. In this numerical study, we present a mitigation strategy based on modulating the pump power. Using as little as three pulses in the modulation scheme, we demonstrate the ability to improve the flatness by a factor of three, while simultaneously lowering the peak power of each pulse, which is desirable from the perspective of fiber degradation.
Laser-ablation is an attractive alternative to abrasive/hydro blasting for the removal of protective coatings from metallic surfaces. However, the ablation process can lead to the formation of potentially hazardous gases, including volatile organic compounds and greenhouse gases. In this work, we investigate femtosecond laser-ablation of marine coatings by analyzing the ultraviolet/visible (UV/VIS) emission from the ablation plasma and performing mid-infrared absorption spectroscopy on the ablation fumes. By identifying the atomic/ionic composition of the plasma and the molecular composition of the fumes, we gain additional insights into the laser-ablation process and potential hazards for human health. This work is supported by VILLUM FONDEN (Villum Investigator project Table-Top Synchrotrons, no. 00037822) and the Danish Maritime Fund (LASER-CLEANR, no. 2022-054).
UV supercontinuum based on gas filled anti resonant hollow core fibers is demonstrated to have passed a major milestone by providing spectral properties comparable to those of plasma arc lamps, namely a broad, flat, low noise, and stable spectrum. The primary advancement is the use of pump modulation which flattens the spectrum by more than 20dB. As proof of concept, results from scatterometry measurements, with both UV supercontinuum and plasma arc lamps are shown to produce comparable results. However, UV supercontinuum can meet additional requirements making it suitable for many cutting-edge UV metrology applications such as imaging and spectroscopy.
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