DOCSLIB.ORG

Time-Resolved Studies of Nd:YAG Loser-Induced Breakdown

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Time-Resolved Studies of Nd:YAG Loser-Induced Breakdown Time-Resolved Studies of Nd:YAG Loser-Induced Breakdown Plasma Formation, Acoustic Wave Generation, and Cavitation Jomes G. Fujimoro,* Wei Z. Liaf Erich P. Ippen,* Carmen A. PuliQfiro4 and Roger F. Sreinerr^: The use of high intensity ultrashort pulsed laser radiation to produce optical breakdown is an important approach for the surgical treatment of intraocular structures. We have investigated the transient properties of Nd:YAG laser induced breakdown in a saline model using time-resolved spectroscopic techniques. Spatially resolved pump and probe techniques are applied to study the dynamic behavior of the plasma formation, acoustic wave generation, and cavitation processes which accompany the optical breakdown. Measurements of plasma shielding and luminescence indicate that the laser induced plasma forms on a subnanosecond time scale and has a lifetime of several nanoseconds. An acoustic transient is generated at the breakdown site and propagates spherically outward with an initial hypersonic velocity, then loses energy and propagates at sound velocity. Transient heating following the plasma formation produces a liquid-gas phase change and gives rise to cavitation or gas bubble formation. This gas bubble expands rapidly for several microseconds, then slows to reach its maximum size and finally collapses. Invest Ophthalmol Vis Sci 26:1771-1777, 1985 Short pulsed Q-switched and modelocked Nd:YAG important role in protecting the retina from the inci- lasers have recently achieved widespread use in dent laser energy,10"12'25"28 while the clinically useful ophthalmic surgery. The ability of high intensity short effects are primarily produced by the acoustic wave laser pulses to induce optical breakdown and produce and cavitation.10111923'28 lesions from acoustic transient and cavitation effects In this paper we describe the experimental investi- has been especially important for the surgical treat- gation of the transient phenomena associated with ment of intraocular structures in the anterior eye which laser-induced optical breakdown through the applica- are nominally transparent to the laser wavelength.1"12 tion of time-resolved spectroscopic techniques. In par- The transient physical phenomena which accompany ticular we emphasize pump-probe measurements as a the optical breakdown process include laser-induced method for characterizing the transient temporal and plasma formation, acoustic wave generation and prop- spatial evolution of the breakdown process. The pump- agation, as well as cavitation or gas bubble forma- probe technique relies on the use of two laser beams: tion.13"28 These processes are relevant to the clinical one beam, the pump, is used to produce a change in effectiveness of optical breakdown and have direct im- the sample, while the other beam, the probe, measures plications on its physiological and pathological effects the effects produced by the pump. In this investigation in the eye. The increased absorption of the laser-in- a Q-switched Nd:YAG is used as the pump laser to duced plasma has been shown to play a potentially induce optical breakdown in a saline sample while a continuous wave HeNe laser is used to measure the transient changes in optical properties. The measure- From the Department of Electrical Engineering and Computer ment of both spatial and temporal behavior allows the Science and Research Laboratory of Electronics,* Massachusetts In- characterization of plasma formation, acoustic wave stitute of Technology, Cambridge, Massachusetts; the Howe Labo- generation, and cavitation which accompany the ratory of Ophthalmology, Massachusetts Eye and Ear Infirmary,! breakdown as well as a determination of the physical Boston, Massachusetts; Visiting from Zhongshan University,! dimensions and propagation velocities associated with Guangzhou, People's Republic of China. Supported in part by the Joint Services Electronics Program under these phenomena. While previous researchers have ex- Grant DAAG 29-83-K-003. amined laser-induced breakdown using a variety of Submitted for publication: January 22, 1985. techniques including high speed photography and ho- Reprint requests: James G. Fujimoto, PhD, Department of Elec- lography,1516'20'21'24 transient luminescence and pulse trical Engineering and Computer Science and Research Laboratory transmission detection,17'26'27 and acoustic transducer of Electronics, Massachusetts Institute of Technology, 77 Massachu- measurements,131419'23 the spatially resolved pump- setts Avenue, Cambridge, MA 02139. 1771 Downloaded from iovs.arvojournals.org on 09/26/2021 1772 INVESTIGATIVE OPHTHALMOLOGY 6 VISUAL SCIENCE / December 1985 Vol. 26 SCHEMATIC OF PUMP - PROBE MEASUREMENT stability. The pulse energy delivered to the sample was varied using beamsplitters and calibrated neutral den- sity filters. Pulse energy measurements were performed with a Scientech Model 361 (Boulder, CO) pyroelectric He-Ne PROBE energy meter. The laser output beam was 10 mm in diameter and focused into the sample cell with a 25- mm focal length lens. Since the Nd:YAG laser em- ployed a diffraction coupled resonator, the spatial mode profile of the output beam was a "doughnut" rather Nd< YAG than a Gaussian mode, and diffraction limit focusing PUMP was not expected. The transient properties of the laser-induced break- down were probed by a low intensity, 1 mW, contin- SAMPLE CELL uous wave helium-neon (HeNe) laser (X = 632.8 nm). In order to obtain a spatial resolution of better than FILTER 10 nm, the probe beam was first expanded to a diameter of 6 mm before being focussed into the sample ceil with a 32-mm focal length lens. The focal point of the FAST PHOTODIODE HeNe probe laser was carefully adjusted to coincide with the center of the breakdown region with the probe beam orthogonal to the pump beam. Since the break- Fig. 1. Schematic diagram of experimental configuration for pump probe time resolved measurements of laser-induced breakdown. Nd: down region extends along the axis of the pump beam YAG laser pump pulses are focused into a sample cell containing with increasing pump pulse energy, the probe align- saline. The transient optical properties are probed by a HeNe laser ment was adjusted after changes in the pump energy. and a high speed photodiode. Spatially resolved measurements are Spatially resolved pump-probe measurements of the performed by displacing the pump and probe laser beams in a di- rection perpendicular to the plane of the figure. breakdown process were obtained by varying the rel- ative separation of the probe laser beam focus from the center of the breakdown region. This was accom- plished by translating the pump beam steering and fo- probe technique is one of the few approaches which cusing optics in a direction orthogonal to the plane of permits the investigation of a wide variety of physical Figure 1 using a l-/um resolution stepping motor me- processes in a simple and consistent experimental chanical stage (Klinger Scientific; Richmond Hill, NY). framework. The center of the breakdown region was determined by noting that the probe beam behavior should be Materials and Methods symmetric for positive and negative displacements. The use of this spatially resolved technique facilitates the The experimental configuration for pump-probe measurement of physical dimensions as well as the dy- measurements of laser-induced optical breakdown is namic behavior of processes involving transient prop- shown schematically (Fig. 1). For our investigations, agation away from the center of the breakdown region. optical breakdown was studied in a simple model sys- The transmitted HeNe probe beam was focussed tem consisting of physiological (0.9%) saline solution. onto a small area, high speed, avalanche photodiode The saline was contained in a 10 X 20-mm quartz flu- detector (Telefunken BPW28; Sommerville, NJ). A orimeter cell. In order to prevent the accumulation of narrowband dielectric interference filter centered at gas bubbles or other impurities produced by the optical 632.8 nm was used to block luminescence and scattered breakdown process, the solution was circulated and light from the optical breakdown. The small area of filtered with a 3-nm filter. the detector combined with this detection geometry A frequency doubled Q-switched Nd:YAG laser makes the probe laser sensitive not only to changes in (Quanta-Ray DCR1; Mountain View, CA) was used transmission arising from induced absorption or scat- as the pump laser to produce optical breakdown in the tering, but also to changes in the index of refraction sample. The Nd:YAG laser generates ~10 ns long which will influence the imaging of the probe beam pulses at 532 nm with a repetition rate of 10 Hz. The onto the detector. The temporal behavior of the laser- second harmonic of the Nd.YAG laser was used in induced plasma luminescence was also measured by order to facilitate accurate measurements of beam spa- turning off the probe laser and using a low pass, red tial profile and focusing characteristics. The laser was filter in front of the detector to block the scattered pump adjusted to optimize temporal pulse shape and energy laser. Downloaded from iovs.arvojournals.org on 09/26/2021 No. 12 ND:YAG LASER-INDUCED BREAKDOWN / Fujimoro er ol. 1773 The output of the photodiode was measured with a high speed oscilloscope (Tektronix 7104; Beaverton, (a) OR) with a 1 GHz bandwidth. Measurements which Nd=YAG PULSE did not require as high temporal resolution were per- formed using a high speed storage oscilloscope (Tek- 5 ns/div tronix 7834). The temporal resolution was ~4 ns as limited by the duration of the Nd:YAG laser pulses. Experimentally, the effective temporal measurement resolution was limited by fluctuations in the laser-in- duced breakdown processes which occurred on a shot (b) to shot basis rather than bandwidth restrictions in the electronic instrumentation. LUMINESCENCE 5 ns/div Results A sharp threshold for the onset of optical breakdown is observed with increasing Nd:YAG pump laser in- tensity. For our experimental conditions, using purified (c) saline solution, threshold was ~-6 mJ per pulse.
Load more

Recommended publications
  • Part 2: Laser in Pulsed Operation
    Part 2: Laser in pulsed operation 1 Theoretical principles 1.1 Generation of short laser pulses The output power of existing continuous wave laser systems is between a few milliwatts (He-Ne lasers) and a few hundred watts (Nd or CO2 lasers). However, there is a possibility to increase the output power of the laser for a small period of time by pulsed laser operation. Solid-state lasers are particularly suitable for this purpose, as they can achieve pulse peak output powers of up to 1012 W. This value corresponds approximately to the average electrical energy generation of the entire world. The difference, however, lies in the period in which this performance is achieved. While all the power plants together reach this value continuously, a single laser produces this high output power only for a duration of 10−13 s. In this case, the extremely short pulse duration appears to be disadvantageous, but there are also applications which exactly require this. One example is laser ablation, which is a method in material processing. Here, a small volume of material at the surface of a work piece can be evaporated if it is heated high enough in a very short amount of time. On the other hand, supplying the energy gradually would allow the heat to be absorbed into the bulk of the piece, never attaining a sufficiently high temperature above the evaporation point of the material. Other applications rely on the very high peak pulse power to obtain strong non-linear optical effects, like it is necessary for efficient second-harmonic generation or for optical parametric oscillators (OPO) which converts an input laser wave into two output waves of lower frequencies.
    [Show full text]
  • Practical Tips for Two-Photon Microscopy
    Appendix 1 Practical Tips for Two-Photon Microscopy Mark B. Cannell, Angus McMorland, and Christian Soeller INTRODUCTION blue and green diode lasers. To provide an alignment beam to which the external laser can be aligned, light from this reference As is clear from a number of the chapters in this volume, 2-photon laser needs to be bounced back through the microscope optical microscopy offers many advantages, especially for living-cell train and out through the external coupling port: studies of thick specimens such as brain slices and embryos. CAUTION: Before you switch on the reference laser in this However, these advantages must be balanced against the fact that configuration make sure that all PMTs are protected and/or commercial multiphoton instrumentation is much more costly than turned off. the equipment used for confocal or widefield/deconvolution. Given Place a front-surface mirror on the stage of the microscope and these two facts, it is not surprising that, to an extent much greater focus onto the reflective surface using an air objective for conve- than is true of confocal, many researchers have decided to add a nience (at sharp focus, you should be able to see scratches or other femtosecond (fs) pulsed near-IR laser to a scanner and a micro- mirror defects through the eyepieces). The idea of this method is scope to make their own system (Soeller and Cannell, 1996; Tsai to cause the reference laser beam to bounce back through the et al., 2002; Potter, 2005). Even those who purchase a commercial optical train and emerge from the other laser port.
    [Show full text]
  • Improved Laser Based Photoluminescence on Single-Walled Carbon Nanotubes
    Improved laser based photoluminescence on single-walled carbon nanotubes S. Kollarics,1 J. Palot´as,1 A. Bojtor,1 B. G. M´arkus,1 P. Rohringer,2 T. Pichler,2 and F. Simon1 1Department of Physics, Budapest University of Technology and Economics and MTA-BME Lend¨uletSpintronics Research Group (PROSPIN), P.O. Box 91, H-1521 Budapest, Hungary 2Faculty of Physics, University of Vienna, Strudlhofgasse 4., Vienna A-1090, Austria Photoluminescence (PL) has become a common tool to characterize various properties of single- walled carbon nanotube (SWCNT) chirality distribution and the level of tube individualization in SWCNT samples. Most PL studies employ conventional lamp light sources whose spectral dis- tribution is filtered with a monochromator but this results in a still impure spectrum with a low spectral intensity. Tunable dye lasers offer a tunable light source which cover the desired excitation wavelength range with a high spectral intensity, but their operation is often cumbersome. Here, we present the design and properties of an improved dye-laser system which is based on a Q-switch pump laser. The high peak power of the pump provides an essentially threshold-free lasing of the dye laser which substantially improves the operability. It allows operation with laser dyes such as Rhodamin 110 and Pyridin 1, which are otherwise on the border of operation of our laser. Our sys- tem allows to cover the 540-730 nm wavelength range with 4 dyes. In addition, the dye laser output pulses closely follow the properties of the pump this it directly provides a time resolved and tunable laser source.
    [Show full text]
  • Two-Photon-Excited Fluorescence (TPEF) and Fluorescence Lifetime Imaging (FLIM) with Sub-Nanosecond Pulses and a High Analog Bandwidth Signal Detection
    Two-photon-excited fluorescence (TPEF) and fluorescence lifetime imaging (FLIM) with sub-nanosecond pulses and a high analog bandwidth signal detection Matthias Eibl1, Sebastian Karpf2, Hubertus Hakert1, Daniel Weng1, and Robert Huber1 1Institut für Biomedizinische Optik, Universität zu Lübeck, Lübeck, Peter-Monnik-Weg 4, 23562 Lübeck, Germany 2Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA ABSTRACT Two-photon excited fluorescence (TPEF) microscopy and fluorescence lifetime imaging (FLIM) are powerful imaging techniques in bio-molecular science. The need for elaborate light sources for TPEF and speed limitations for FLIM, however, hinder an even wider application. We present a way to overcome this limitations by combining a robust and inexpensive fiber laser for nonlinear excitation with a fast analog digitization method for rapid FLIM imaging. The applied sub nanosecond pulsed laser source is synchronized to a high analog bandwidth signal detection for single shot TPEF- and single shot FLIM imaging. The actively modulated pulses at 1064nm from the fiber laser are adjustable from 50ps to 5ns with kW of peak power. At a typically applied pulse lengths and repetition rates, the duty cycle is comparable to typically used femtosecond pulses and thus the peak power is also comparable at same cw-power. Hence, both types of excitation should yield the same number of fluorescence photons per time on average when used for TPEF imaging. However, in the 100ps configuration, a thousand times more fluorescence photons are generated per pulse. In this paper, we now show that the higher number of fluorescence photons per pulse combined with a high analog bandwidth detection makes it possible to not only use a single pulse per pixel for TPEF imaging but also to resolve the exponential time decay for FLIM.
    [Show full text]
  • Angwcheminted, 2000, 39, 2587-2631.Pdf
    REVIEWS Femtochemistry: Atomic-Scale Dynamics of the Chemical Bond Using Ultrafast Lasers (Nobel Lecture)** Ahmed H. Zewail* Over many millennia, humankind has biological changes. For molecular dy- condensed phases, as well as in bio- thought to explore phenomena on an namics, achieving this atomic-scale res- logical systems such as proteins and ever shorter time scale. In this race olution using ultrafast lasers as strobes DNA structures. It also offers new against time, femtosecond resolution is a triumph, just as X-ray and electron possibilities for the control of reactivity (1fs 10À15 s) is the ultimate achieve- diffraction, and, more recently, STM and for structural femtochemistry and ment for studies of the fundamental and NMR spectroscopy, provided that femtobiology. This anthology gives an dynamics of the chemical bond. Ob- resolution for static molecular struc- overview of the development of the servation of the very act that brings tures. On the femtosecond time scale, field from a personal perspective, en- about chemistryÐthe making and matter wave packets (particle-type) compassing our research at Caltech breaking of bonds on their actual time can be created and their coherent and focusing on the evolution of tech- and length scalesÐis the wellspring of evolution as a single-molecule trajec- niques, concepts, and new discoveries. the field of femtochemistry, which is tory can be observed. The field began the study of molecular motions in the with simple systems of a few atoms and Keywords: femtobiology ´ femto- hitherto unobserved ephemeral transi- has reached the realm of the very chemistry ´ Nobel lecture ´ physical tion states of physical, chemical, and complex in isolated, mesoscopic, and chemistry ´ transition states 1.
    [Show full text]
  • Tutorial: Fiber Laser Basics
    Tutorial: fiber laser basics Fiber lasers: this tutorial provides an overview of the technical approaches most commonly used to make a fiber laser. It explains the component choices and various architectures that are generally used for CW or pulsed fiber laser development. I. Fiber lasers principles: A fiber laser is a laser in which the amplifying media is an optical fiber. It is an active module (like an active electronic component in electronics) that needs to be powered and which uses the properties of optical amplification of Rare-Earth ions. The pumping media is generally a fiber-coupled laser diode. Two kinds of architectures can be utilized: • Laser cavity configurations where the light goes in both directions through the fiber amplifying media. • MOPA configurations: (Master Oscillator Power Amplifier) where an oscillating media generates a small “seeder” signal which is amplified through the fiber amplifying media. Figure1: Fiber laser in laser cavity configuration Figure 2: Fiber laser in a MOPA configuration (Master Oscillator Power Amplifier) – single stage version www.AeroDIODE.com II. Key components of fiber lasers: This section explains the various elements shown in Figure1 and Figure 2. It includes some examples of alternative supplier categories and choices. a) Fiber amplifying media As with any laser, a fiber laser uses the principle of stimulated emission. Most fiber lasers are made from a concatenation of fiber-coupled components. The fibers associated with the various components are called “passive fibers”. Passive fibers have no amplification properties. The fibers at the heart of the amplifying media are called “active fibers”. Active fibers are doped with rare-earth elements (like Erbium, Ytterbium or Thulium) which perform the stimulated emission by transforming the laser diode pumping power to the laser power.
    [Show full text]
  • From Pulsed to Continuous Wave Emission in SLM with Contemporary Fiber Laser Sources: Effect of Temporal and Spatial Pulse Overlap in Part Quality
    From pulsed to continuous wave emission in SLM with contemporary fiber laser sources: effect of temporal and spatial pulse overlap in part quality Demir, ALI GOKHAN; Colombo, Paolo; Previtali, Barbara This is a post-peer-review, pre-copyedit version of an article published in INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY. The final authenticated version is available online at: http://dx.doi.org/10.1007/s00170-016-9948-7 This content is provided under CC BY-NC-ND 4.0 license DIPARTIMENTO DI MECCANICA ◼ POLITECNICO DI MILANO via G. La Masa, 1 ◼ 20156 Milano ◼ EMAIL (PEC): [email protected] http://www.mecc.polimi.it Rev. 0 From pulsed to continuous wave emission in SLM with contemporary fiber laser sources: Effect of temporal and spatial pulse overlap in part quality Ali Gökhan Demir*, [email protected] Paolo Colombo, [email protected] Barbara Previtali, [email protected] Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, 20156 Milan, Italy *Corresponding author 1 From pulsed to continuous wave emission in SLM with contemporary fiber laser sources: Effect of temporal and spatial pulse overlap in part quality Ali Gökhan Demir*, [email protected] Paolo Colombo, [email protected] Barbara Previtali, [email protected] Department of Mechanical Engineering, Politecnico di Milano, Via La Masa 1, 20156 Milan, Italy *Corresponding author Abstract In this work, the effect of pulse temporal and spatial overlapping is evaluated in selective laser melting (SLM). An SLM system operating with fiber laser in pulsed wave (PW) emission was employed. The test material was 18Ni300 maraging steel, which shows reduced process stability due to a high amount of vapour and spark generation during the process.
    [Show full text]
  • Passively Q-Switched Ytterbium-Doped Fiber Laser
    www.nature.com/scientificreports OPEN Passively Q-switched Ytterbium- doped fber laser based on broadband multilayer Platinum Received: 13 March 2019 Accepted: 3 July 2019 Ditelluride (PtTe2) saturable Published: xx xx xxxx absorber Ping Kwong Cheng1,2, Chun Yin Tang1,2, Xin Yu Wang1,2, Sainan Ma1,2, Hui Long1,2 & Yuen Hong Tsang 1,2 Two-dimensional (2D) layered Platinum Ditelluride (PtTe2), a novel candidate of group 10 transition- metal dichalcogenides (TMDs), which provides enormous potential for pulsed laser applications due to its highly stable and strong nonlinear optical absorption (NOA) properties. PtTe2 saturable absorber (SA) is successfully fabricated with frstly demonstrated the passively Q-switched laser operation within a Yb-doped fber laser cavity at 1066 nm. Few layered PtTe2 is produced by uncomplicated and cost- efcient ultrasonic liquid exfoliation and follow by incorporating into polyvinyl alcohol (PVA) polymer to form a PtTe2-PVA composite thin flm saturable absorber. The highest achieved single pulse energy is 74.0 nJ corresponding to pulse duration, repetition rate and average output power of 5.2 μs, 33.5 kHz and 2.48 mW, respectively. This work has further exploited the immeasurable utilization potential of the air stable and broadband group 10 TMDs for ultrafast photonic applications. Q-switching, a useful and very important technique, has been widely studied and applied in pulsed laser devel- opment over the past decades1–4. Contributed by the remarkable high pulse peak power, Q-switched laser can be employed in vast applications, for instance, industrial laser engraving, nonlinear optics, skin treatment, and eyes surgery5–7. Q-switched laser pulses can be produced by using Acousto-optical or Electro-optical modulators (AOM/EOM)8 to actively modify the Quality factor within the cavity.
    [Show full text]
  • Ultrafast Fiber Lasers with Low-Dimensional Saturable Absorbers: Status and Prospects
    sensors Review Ultrafast Fiber Lasers with Low-Dimensional Saturable Absorbers: Status and Prospects Pulak Chandra Debnath 1,2 and Dong-Il Yeom 1,2,* 1 Department of Energy Systems Research, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499, Korea; [email protected] 2 Department of Physics, Ajou University, 206 Worldcup-ro, Yeongtong-gu, Suwon 16499, Korea * Correspondence: [email protected]; Tel.: +82-31-219-1937 Abstract: Wide-spectral saturable absorption (SA) in low-dimensional (LD) nanomaterials such as zero-, one-, and two-dimensional materials has been proven experimentally with outstanding results, including low saturation intensity, deep modulation depth, and fast carrier recovery time. LD nanomaterials can therefore be used as SAs for mode-locking or Q-switching to generate ultrafast fiber laser pulses with a high repetition rate and short duration in the visible, near-infrared, and mid- infrared wavelength regions. Here, we review the recent development of emerging LD nanomaterials as SAs for ultrafast mode-locked fiber laser applications in different dispersion regimes such as anomalous and normal dispersion regimes of the laser cavity operating in the near-infrared region, especially at ~1550 nm. The preparation methods, nonlinear optical properties of LD SAs, and various integration schemes for incorporating LD SAs into fiber laser systems are introduced. In addition to these, externally (electrically or optically) controlled pulsed fiber laser behavior and other characteristics of various LD SAs are summarized. Finally, the perspectives and challenges facing LD SA-based mode-locked ultrafast fiber lasers are highlighted. Citation: Debnath, P.C.; Yeom, D.-I. Ultrafast Fiber Lasers with Keywords: ultrafast fiber laser; saturable absorber; low-dimensional materials; optically/electrically Low-Dimensional Saturable controlled fiber lasers Absorbers: Status and Prospects.
    [Show full text]
  • Wide Band, High Efficiency Simmer Power Supply for a Laser Flashlamp
    Europaisches Patentamt llll III European Patent Office HUM llllll II Hill Hill Hill Hill lllll Hill lllll lllll llllll llll Office europeen des brevets (ff) Publication number: 0 250 464 B1 © EUROPEAN PATENT SPECIFICATION @ Date of publication of patent specification : @ Int CI.5 : H05B 41/34 18.09.91 Bulletin 91/38 (21) Application number : 86906527.6 (22) Date of filing : 29.09.86 (86) International application number: PCT/US86/02027 (87) International publication number: WO 87/04038 02.07.87 Gazette 87/14 (g) WIDE BAND, HIGH EFFICIENCY SIMMER POWER SUPPLY FOR A LASER FLASHLAMP. (§) Priority : 17.12.85 US 810399 (73) Proprietor : Hughes Aircraft Company 7200 Hughes Terrace P.O. Box 45066 Los Angeles, California 90045-0066 (US) © Date of publication of application : 07.01.88 Bulletin 88/01 (72) Inventor: FARNSWORTH, Robert, P. 12612 Indianapolis St @ Publication of the grant of the patent : Los Angeles, CA 90066 (US) 18.09.91 Bulletin 91/38 (74) Representative : Kuhnen, Wacker & Partner (3) Designated Contracting States : Schneggstrasse 3-5 Postfach 1553 BE CH DE FR GB IT LI NL SE W-8050 Freising (DE) (5§) References cited : WO-A-81/03596 WO-A-83/00596 GB-A- 2 095 930 00 CD in Note : Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Q. Notice of opposition shall be filed in a written reasoned statement It shall not be deemed to have been LU filed until the opposition fee has been paid (Art.
    [Show full text]
  • Novel Technologies for Mode-Locking of Solid-State Lasers
    Novel Technologies for Mode-Locking of Solid-State Lasers NIELS MEISER Doctoral Thesis Department of Applied Physics KTH – Royal Institute of Technology Stockholm, Sweden 2013 Novel Technologies for Mode-Locking of Solid-State Lasers © Niels Meiser, 2013 Laser Physics Department of Applied Physics KTH – Royal Institute of Technology 106 91 Stockholm Sweden ISBN 978-91-7501-840-9 TRITA-FYS 2013:48 ISSN 0280-316X ISRN KTH/FYS/--13:48—SE Akademisk avhandling som med tillstånd av Kungliga Tekniska Högskolan framlägges till offentlig granskning för avläggande av teknologie doktorsexamen tisdagen den 5 november kl. 10:00 i sal FA32, Albanova, Roslagstullsbacken 21, KTH, Stockholm. Avhandlingen kommer att försvaras på engelska. Printed by Universitetsservice US AB, Stockholm 2013 Niels Meiser Novel Technologies for Mode-Locking of Solid-State Lasers Laser Physics, Department of Applied Physics, KTH – Royal Institute of Technology, 106 91 Stockholm, Sweden ISBN 978-91-7501-840-9, TRITA-FYS 2013:48, ISSN 0280-316X, ISRN KTH/FYS/--13:48—SE Abstract The subject of this thesis is the investigation of novel technologies for mode-locking of diode-pumped, solid-state lasers. Novel saturable absorbers are used: quantum dots (QDs) and carbon nanotubes (CNTs), which both are low-dimensional nano- formations. In addition, mode-locking by cascaded nonlinearities is explored. Absorber structures containing self-assembled InGaAs QDs are characterised in detail by pump-probe experiments, time-resolved photoluminescence spectroscopy, and measurement of the nonlinear reflectivity. The samples show sub-picosecond relaxation times of the reflectivity, modulation depths between 0.18 % and 2.9 %, as well as low saturation fluences on the order of 1–10 µJ/cm2.
    [Show full text]
  • Fiber Laser Basics
    Tutorial: fiber laser basics This tutorial provides an overview of the technical approaches most commonly used to make a fiber laser. The components choices and various architectures that are generally used for any ranges of CW or pulsed fiber laser optical performances are described. I. Fiber lasers principles : A fiber laser is a laser where the amplifying media is an optical fiber. It is an active module (like an active electronic component in electronics) that needs to be powered and which uses the properties of optical amplifications of Rare-Earth ions. The pumping media is generally a fiber-coupled laser diode. Two kinds of architectures can be met : • Laser cavity configurations where the light goes in both direction through the fiber amplifying media. • MOPA configurations (Master Oscillator Power Amplifier) where an oscillating media generates a small “seeder” signal which is amplified through the fiber amplifying media. Figure 1 : Fiber laser in laser cavity configuration Figure 2 :Fiber laser in a MOPA configuration (Master Oscillator Power Amplifier) – single stage version ALPhANOV - Institut d’optique d’Aquitaine - Rue François Mitterrand 33400 Talence - France - Tél.: +33 (0)5 24 54 52 00 [email protected] - www.alphanov.com SIRET 493 635 817 00031 - N° TVA intracommunautaire : FR 24493635817 II. Fiber lasers key components : The various elements of Figure 1 and Figure 2 with some examples of alternative supplier categories and choices are described hereafter. a) Fiber amplifying media As for any laser, a fiber laser uses the principle of stimulated emission. The majority of the fiber laser are made of a concatenation of fiber-coupled components.
    [Show full text]