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Author

Lawrence Shah

Other affiliations: University of Toronto
Bio: Lawrence Shah is an academic researcher from University of Central Florida. The author has contributed to research in topics: Fiber laser & Laser. The author has an hindex of 29, co-authored 178 publications receiving 3760 citations. Previous affiliations of Lawrence Shah include University of Toronto.


Papers
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Journal ArticleDOI
TL;DR: High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses and accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate.
Abstract: High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses. A novel femtosecond fiber laser system (IMRA America, FCPA muJewel) providing variable repetition rate between 0.1 and 5 MHz was used to study the relationship between heat accumulation and resulting waveguide properties in fused silica and various borosilicate glasses. Increasing repetition rate was seen to increase the waveguide diameter and decrease the waveguide loss, with waveguides written with 1-MHz repetition rate yielding ~0.2-dB/cm propagation loss in Schott AF45 glass. A finite-difference thermal diffusion model accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate.

732 citations

Journal ArticleDOI
TL;DR: In this paper, the relationship between the laser process conditions and the dimensions and quality of the seam was investigated by means of optical and phase-contrast microscopy, which revealed a tensile strength of greater than 80% of the bulk material strength.
Abstract: Absorber-free transmission and butt-welding of different polymers were performed using thulium fiber laser radiation at the wavelength 2 μm. The relations between the laser process conditions and the dimensions and quality of the seam were investigated by means of optical and phase-contrast microscopy. Mechanical properties of the weld joints were studied in tensile strength tests. Laser-welded polyethylene samples revealed a tensile strength of greater than 80% of the bulk material strength. Transmission welding of different polymer combinations featured the formation of different joint classes depending on the spectral properties. The experiments demonstrate new application areas of mid-IR fiber laser sources for materials processing.

256 citations

Patent
19 Dec 2008
TL;DR: In this paper, the authors describe classes of robust fiber laser systems usable as pulse sources for Nd: or Yb: based regenerative amplifiers intended for industrial settings, and modifies adapts and incorporates several recent advances in FCPA systems to use as the input source for this new class of regenerative amplifier.
Abstract: The invention describes classes of robust fiber laser systems usable as pulse sources for Nd: or Yb: based regenerative amplifiers intended for industrial settings. The invention modifies adapts and incorporates several recent advances in FCPA systems to use as the input source for this new class of regenerative amplifier.

208 citations

Journal ArticleDOI
TL;DR: Waveguide writing in fused silica with a novel commercial femtosecond fiber laser system (IMRA America, FCPA microJewel) and the influence of a range of laser parameters were investigated, finding that it was not possible to produce low-loss waveguides when writing with the fundamental wavelength of 1045 nm, but it was possible to fabricate telecom-compatible waveguide at the second harmonic wavelength of 522 nm.
Abstract: We report on waveguide writing in fused silica with a novel commercial femtosecond fiber laser system (IMRA America, FCPA microJewel) The influence of a range of laser parameters were investigated in these initial experiments, including repetition rate, focal area, pulse energy, scan speed, and wavelength Notably, it was not possible to produce low-loss waveguides when writing with the fundamental wavelength of 1045 nm However, it was possible to fabricate telecom-compatible waveguides at the second harmonic wavelength of 522 nm High quality waveguides with propagation losses below 1 dB/cm at 1550 nm were produced with 115 nJ/pulse at 1 MHz and 522 nm

190 citations

Patent
14 Mar 2005
TL;DR: In this paper, a femtosecond laser based laser processing system has been proposed for the utilization of the unique heat control in micromachining, and the system has greater output beam stability, continuously variable repetition rate and unique temporal beam shaping capabilities.
Abstract: A femtosecond laser based laser processing system having a femtosecond laser, frequency conversion optics, beam manipulation optics, target motion control, processing chamber, diagnostic systems and system control modules. The femtosecond laser based laser processing system allows for the utilization of the unique heat control in micromachining, and the system has greater output beam stability, continuously variable repetition rate and unique temporal beam shaping capabilities.

190 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the physical mechanisms and the main experimental parameters involved in femtosecond laser micromachining of transparent materials, and important emerging applications of the technology are described.
Abstract: Femtosecond laser micromachining can be used either to remove materials or to change a material's properties, and can be applied to both absorptive and transparent substances. Over the past decade, this technique has been used in a broad range of applications, from waveguide fabrication to cell ablation. This review describes the physical mechanisms and the main experimental parameters involved in the femtosecond laser micromachining of transparent materials, and important emerging applications of the technology. Interactions between laser and matter are fascinating and have found a wide range of applications. This article gives an overview of the fundamental physical mechanisms in the processing of transparent materials using ultrafast lasers, as well as important emerging applications of the technology.

2,533 citations

Journal ArticleDOI
TL;DR: In this article, a review summarizes the different rare-earth cations and host materials used in mid-infrared fiber laser technology, and discusses the future applications and challenges for the field.
Abstract: Fibre lasers in the mid-infrared regime are useful for a diverse range of fields, including chemical and biomedical sensing, military applications and materials processing. This Review summarizes the different rare-earth cations and host materials used in mid-infrared fibre laser technology, and discusses the future applications and challenges for the field.

974 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the characteristics of ultrafast laser processing and the recent advancements and applications of both surface and volume processing is presented, and a summary of the technology with future outlooks are also given.
Abstract: The unique characteristics of ultrafast lasers, such as picosecond and femtosecond lasers, have opened up new avenues in materials processing that employ ultrashort pulse widths and extremely high peak intensities. Thus, ultrafast lasers are currently used widely for both fundamental research and practical applications. This review describes the characteristics of ultrafast laser processing and the recent advancements and applications of both surface and volume processing. Surface processing includes micromachining, micro- and nanostructuring, and nanoablation, while volume processing includes two-photon polymerization and three-dimensional (3D) processing within transparent materials. Commercial and industrial applications of ultrafast laser processing are also introduced, and a summary of the technology with future outlooks are also given. Scientists in Asia have reviewed the role of ultrafast lasers in materials processing. Koji Sugioka from RIKEN in Japan and Ya Cheng from the Shanghai Institute of Optics and Fine Mechanics in China describe how femtosecond and picosecond lasers can be used to perform useful tasks in both surface and volume processing. Such lasers can cut, drill and ablate a variety of materials with high precision, including metals, semiconductors, ceramics and glasses. They can also polymerize organic materials that contain a suitable photosensitizer and can three-dimensionally process inside transparent materials such as glass, and are already being used to fabricate medical stents, repair photomasks, drill ink-jet nozzles and pattern solar cells. The researchers also explain the characteristics of such lasers and the interaction of ultrashort, intense pulses of light with matter.

973 citations

Journal ArticleDOI
TL;DR: High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses and accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate.
Abstract: High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses. A novel femtosecond fiber laser system (IMRA America, FCPA muJewel) providing variable repetition rate between 0.1 and 5 MHz was used to study the relationship between heat accumulation and resulting waveguide properties in fused silica and various borosilicate glasses. Increasing repetition rate was seen to increase the waveguide diameter and decrease the waveguide loss, with waveguides written with 1-MHz repetition rate yielding ~0.2-dB/cm propagation loss in Schott AF45 glass. A finite-difference thermal diffusion model accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate.

732 citations

Book
04 Jan 2005

644 citations