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Applied Sciences
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Ti:Sapphire Lasers and Their Applications
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Ti:Sapphire Lasers and Their Applications

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 12580

Special Issue Editors

Dr. Volker Sonnenschein

E-Mail Website
Guest Editor
Department of Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
Interests: cavity-enhanced spectroscopy; laser stabilization; optical feedback; nuclear structure; radioisotope trace analysis
Dr. Hideki Tomita

E-Mail Website
Guest Editor
Department of Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
Interests: radioisotope trace analysis; laser spectroscopy; nuclear engineering
Dr. Ryohei Terabayashi

E-Mail Website
Guest Editor
The Nuclear Professional School, The University of Tokyo, Shirakata-Sirane 2-22, Tokai, Ibaraki 319-1188, Japan
Interests: laser spectroscopy; radioisotope analysis; nuclear decommissioning; optical frequency comb; laser locking/frequency stabilization

Special Issue Information

Dear Colleagues,

Ti:sapphire laser technology has matured, with many commercial ‘turn-key’ systems available to end-users. This has increased adoption in many application fields, such as multiphoton microscopy for biomedicine, Terahertz generation, and micromachining, as well as cutting-edge quantum optics research. Despite this maturity, new original developments of Ti:sapphire laser technology are still progressing rapidly. New pumping sources, such as (In)GaN laser diodes and LEDs, show promise to replace traditionally expensive frequency-converted Nd:YAG lasers. Advances in chirped pulse amplification have brought Ti:sapphire to the extreme intensities of Petawatt-class systems for nuclear fusion and fundamental physics research.

This Special Issue, entitled “Ti:Sapphire Lasers and Their Applications”, of Applied Sciences aims to gather original research manuscripts within a broad scope covering both laser development and applications, as well as a select choice of review articles.

Dr. Volker Sonnenschein
Dr. Hideki Tomita
Dr. Ryohei Terabayashi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • titanium sapphire
  • femtosecond
  • ultrafast
  • spectroscopy
  • oscillator
  • amplifier
  • diode pumping
  • solid-state laser
  • multiphoton
  • optical cavity
  • frequency comb
  • mode locking
  • Kerr lens
  • frequency stabilization

Published Papers (5 papers)

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Research

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27 pages, 5649 KiB  
Article
Erosion Rate Measurements for DART Spacecraft Ion Propulsion System
by Mark W. Crofton, Donner T. Schoeffler, Jason A. Young and Michael J. Patterson
Appl. Sci. 2022, 12(15), 7831; https://doi.org/10.3390/app12157831 - 4 Aug 2022
Cited by 2 | Viewed by 1434
Abstract
The Double Asteroid Redirection Test (DART) spacecraft was developed to provide the first measurement for orbital deflection of an asteroid upon intentional impact. The NEXT ion engine is part of the mission, on its maiden voyage. As part of the pre-launch risk reduction, [...] Read more.
The Double Asteroid Redirection Test (DART) spacecraft was developed to provide the first measurement for orbital deflection of an asteroid upon intentional impact. The NEXT ion engine is part of the mission, on its maiden voyage. As part of the pre-launch risk reduction, erosion characteristics of the extraction grid system were evaluated using laser measurements of sputtered molybdenum atoms over the envelope of potential throttle conditions for the mission. Erosion rate dependence on propellant flow rate as well as relative density and directionality of molybdenum sputter from grid center to edge were measured. Sputtered atoms were found to have average radial velocity directed toward the engine perimeter and increasing with radial distance. The relative contribution of source and facility background gas and other sources of accelerator grid current was examined as well as the influence of several engine operating parameters. Facility background gas was found to influence engine operation more than a wall-mounted pressure gauge and typical assumptions about ingestion would indicate. Far-field flux was estimated over the full angular range based on the near-field relative density and velocity results and relying on quartz crystal microbalance data at one location to fix absolute numbers everywhere. The results substantially deepen knowledge and understanding of the complex grid erosion process of the engine and its lifetime, as grid failure via erosion is the normal life limiter. Study results are also relevant to thruster–spacecraft integration issues such as molybdenum deposition rate on solar cells and other spacecraft surfaces. Full article
(This article belongs to the Special Issue Ti:Sapphire Lasers and Their Applications)
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20 pages, 7893 KiB  
Article
Morphology of Meteorite Surfaces Ablated by High-Power Lasers: Review and Applications
by Anna Křivková, Vojtěch Laitl, Elias Chatzitheodoridis, Lukáš Petera, Petr Kubelík, Antonín Knížek, Homa Saeidfirozeh, Barbora Drtinová, Václav Čuba, Dan Páclík, Tomáš Mocek, Jan Brajer, Jan Kaufman, Martin Divoký, Jakub Koukal, Roman Dudžák, Nikola Schmidt, Petr Boháček, Svatopluk Civiš, Libor Lenža, Miroslav Krůs and Martin Ferusadd Show full author list remove Hide full author list
Appl. Sci. 2022, 12(10), 4869; https://doi.org/10.3390/app12104869 - 11 May 2022
Cited by 2 | Viewed by 2081
Abstract
Under controlled laboratory conditions, lasers represent a source of energy with well-defined parameters suitable for mimicking phenomena such as ablation, disintegration, and plasma formation processes that take place during the hypervelocity atmospheric entry of meteoroids. Furthermore, lasers have also been proposed for employment [...] Read more.
Under controlled laboratory conditions, lasers represent a source of energy with well-defined parameters suitable for mimicking phenomena such as ablation, disintegration, and plasma formation processes that take place during the hypervelocity atmospheric entry of meteoroids. Furthermore, lasers have also been proposed for employment in future space exploration and planetary defense in a wide range of potential applications. This highlights the importance of an experimental investigation of lasers’ interaction with real samples of interplanetary matter: meteorite specimens. We summarize the results of numerous meteorite laser ablation experiments performed by several laser sources—a femtosecond Ti:Sapphire laser, the multislab ceramic Yb:YAG Bivoj laser, and the iodine laser known as PALS (Prague Asterix Laser System). The differences in the ablation spots’ morphology and their dependence on the laser parameters are examined via optical microscopy, scanning electron microscopy, and profilometry in the context of the meteorite properties and the physical characteristics of laser-induced plasma. Full article
(This article belongs to the Special Issue Ti:Sapphire Lasers and Their Applications)
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18 pages, 3727 KiB  
Article
High-Efficiency Continuous-Wave Ti:Sapphire Laser with High-Intensity Pumping Using a Commercially Available Crystal
by Sakae Kawato and Toshiki Kawashima
Appl. Sci. 2022, 12(10), 4815; https://doi.org/10.3390/app12104815 - 10 May 2022
Cited by 1 | Viewed by 3225
Abstract
Despite the importance of improving the efficiency of lasers in order to expand their utility range, the improvement of the efficiency of Ti:sapphire lasers has not progressed due to their high crystal losses. Therefore, we improved the efficiency of CW Ti:sapphire lasers by [...] Read more.
Despite the importance of improving the efficiency of lasers in order to expand their utility range, the improvement of the efficiency of Ti:sapphire lasers has not progressed due to their high crystal losses. Therefore, we improved the efficiency of CW Ti:sapphire lasers by high-intensity pumping, which is one of the most effective methods of suppressing the efficiency reduction due to losses. Using a easily commercially available 0.25 wt.%, figure of merit (FOM) 200 Ti:sapphire crystal, optics and a pump source, we achieved an optical-to-optical conversion efficiency of 32.4% with a slope efficiency of 42.5% at an incident pump power of 5.0 W which corresponds the maximum pumping intensity of 860 kW/cm2. Furthermore, we ensured the reliability of our theoretical analysis by reproducing the experimental results. From this reliable theory, double-pass pumping and increasing the pump power to 25 W resulted in the highest optical-to-optical conversion and slope efficiencies for the incident pump power of 55.9% and 59.6%, respectively, at a high intrinsic residual loss of 4.0%. Even if losses doubled or deviated from the optimum condition for the highest efficiency, the efficiency reduction due to these factors was only a few percent. These results show that with high-intensity pumping, lasers with efficiencies well exceeding half of the quantum limit can be achieved even if all components, including Ti:sapphire crystals, are easily commercially available. Full article
(This article belongs to the Special Issue Ti:Sapphire Lasers and Their Applications)
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12 pages, 2816 KiB  
Article
A Hybrid Self-Seeded Ti:sapphire Laser with a Pumping Scheme Based on Spectral Beam Combination of Continuous Wave Diode and Pulsed DPSS Lasers
by Volker Sonnenschein and Hideki Tomita
Appl. Sci. 2022, 12(9), 4727; https://doi.org/10.3390/app12094727 - 7 May 2022
Cited by 5 | Viewed by 2177
Abstract
A wide variety of applications require high peak laser intensity in conjunction with a narrow spectral linewidth. Typically, injection-locked amplifiers have been employed for this purpose, where a continuous wave oscillator is amplified in a secondary external resonant amplifier cavity using a pulsed [...] Read more.
A wide variety of applications require high peak laser intensity in conjunction with a narrow spectral linewidth. Typically, injection-locked amplifiers have been employed for this purpose, where a continuous wave oscillator is amplified in a secondary external resonant amplifier cavity using a pulsed pump laser. In contrast, here we demonstrate a setup that combines a CW Ti:sapphire oscillator and pulsed amplifier in a single optical cavity, resulting in a compact system. Dichroic beam combination of blue wavelength semiconductor diodes and the green wavelength of a Nd:YAG laser allowed the simultaneous excitation of the Ti:sapphire crystal by both continuous wave and pulsed pump sources. A linewidth of <2 MHz is achieved in continuous wave operation, while the linewidth increases to about 10 MHz in the combined CW+pulsed mode with a pulse duration of 73 ns. A peak pulse intensity of 0.2 kW is achieved, which should enable efficient single-pass second harmonic generation in a nonlinear crystal. Full article
(This article belongs to the Special Issue Ti:Sapphire Lasers and Their Applications)
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Review

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18 pages, 762 KiB  
Review
Engineering of Ti:Sapphire Lasers for Dermatology and Aesthetic Medicine
by Aleksandr Tarasov and Hong Chu
Appl. Sci. 2021, 11(22), 10539; https://doi.org/10.3390/app112210539 - 9 Nov 2021
Cited by 1 | Viewed by 2238
Abstract
This review describes new engineering solutions for Ti:Sapphire lasers obtained at Laseroptek during the development of laser devices for dermatology and aesthetic medicine. The first device, PALLAS, produces 311 nm radiation by the third harmonic generation of a Ti:Sapphire laser, which possesses similar [...] Read more.
This review describes new engineering solutions for Ti:Sapphire lasers obtained at Laseroptek during the development of laser devices for dermatology and aesthetic medicine. The first device, PALLAS, produces 311 nm radiation by the third harmonic generation of a Ti:Sapphire laser, which possesses similar characteristics to excimer laser-based medical devices for skin treatments. In comparison to excimer lasers, Ti:Sapphire laser services are less expensive, which can save ~10% per year for customers compared to initial excimer laser costs. Here, the required characteristics were obtained due to the application of a new type of diffraction grating for spectral selection. The second device, HELIOS-4, based on the Ti:Sapphire laser, produces 300 mJ, 0.5 ns pulses at 785 nm for tattoo removal. The characteristics of HELIOS-4 exceed those of other tattoo removal laser devices represented in the medical market, despite a simple and inexpensive technical solution. The development of the last laser required the detailed study of a generation process and the investigation of the factors responsible for the synchronization of the generation in Ti:Sapphire lasers with short (several millimeters) cavities. The mechanism that can explain the synchronization in such lasers is suggested. Experiments for the confirmation of this concept are conducted and analyzed. Full article
(This article belongs to the Special Issue Ti:Sapphire Lasers and Their Applications)
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