LASER SYSTEMS FOR APPLICATIONS Edited by Krzysztof Jakubczak Laser Systems for Applications Edited by Krzysztof Jakubczak Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2011 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. 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First published December, 2011 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechweb.org Laser Systems for Applications, Edited by Krzysztof Jakubczak p. cm. ISBN 978-953-307-429-0 free online editions of InTech Books and Journals can be found at www.intechopen.com Contents Preface IX Part 1 Laser and Terahertz Sources 1 Chapter 1 Q-Switching with Single Crystal Photo-Elastic Modulators 3 F. Bammer, T. Schumi, J. R. Carballido Souto, J. Bachmair, D. Feitl, I. Gerschenson, M. Paul and A. Nessmann Chapter 2 Acousto-Optically Q-Switched CO 2 Laser 17 Jijiang Xie and Qikun Pan Chapter 3 Mode-Locked Fibre Lasers with High-Energy Pulses 39 S.V.Smirnov, S.M. Kobtsev, S.V.Kukarin and S.K.Turitsyn Chapter 4 All-Poly-Crystalline Ceramics Nd:YAG/Cr 4+ :YAG Monolithic Micro-Lasers with Multiple-Beam Output 59 Nicolaie Pavel, Masaki Tsunekane and Takunori Taira Chapter 5 Laser Pulses for Compton Scattering Light Sources 83 Sheldon S. Q. Wu, Miroslav Y. Shverdin, Felicie Albert and Frederic V. Hartemann Chapter 6 Frequency-Tunable Coherent THz-Wave Pulse Generation Using Two Cr:Forsterite Lasers with One Nd:YAG Laser Pumping and Applications for Non-Destructive THz Inspection 119 Tadao Tanabe and Yutaka Oyama Part 2 Laser Beam Manipulation 137 Chapter 7 Laser Pulse Contrast Ratio Cleaning in 100 TW Scale Ti: Sapphire Laser Systems 139 Sylvain Fourmaux, Stéphane Payeur, Philippe Lassonde, Jean-Claude Kieffer and François Martin Chapter 8 Controlling the Carrier-Envelope Phase of Few-Cycle Laser Beams in Dispersive Media 155 Carlos J. Zapata-Rodríguez and Juan J. Miret VI Contents Chapter 9 Laser Beam Shaping by Interference: Desirable Pattern 171 Liubov Kreminska Chapter 10 Nonlinear Pulse Reshaping in Optical Fibers 185 S. O. Iakushev, I. A. Sukhoivanov, O. V. Shulika, J. A. Andrade-Lucio and A.G. Perez Part 3 Intense Pulse Propagation Phenomena 207 Chapter 11 Linear and Nonlinear Femtosecond Optics in Isotropic Media - Ionization-Free Filamentation 209 Kamen Kovachev and Lubomir M. Kovachev Chapter 12 Dispersion of a Laser Pulse at Propagation Through an Image Acquisition System 227 Toadere Florin Chapter 13 Third-Order Optical Nonlinearities of Novel Phthalocyanines and Related Compounds 253 Zhongyu Li, Zihui Chen, Song Xu, Xinyu Zhou and Fushi Zhang Chapter 14 Broadband Instability of Electromagnetic Waves in Nonlinear Media 271 Sergey Vlasov, Elena Koposova and Alexey Babin Part 4 Metrology 289 Chapter 15 Quantification of Laser Polarization by Position Dependent Refractive Indices 291 Yong Woon Parc and In Soo Ko Preface Well known and established techniques, which allow obtaining intense laser pulses, have led to the development of advanced laser system used in science and various industries. Often at times, they combine Q-switching and mode-locking techniques in a single device to achieve unprecedented average pulse powers (e.g. HiLASE, HiPER, ELI, NIF, LiFE) for scientific applications, such as secondary sources of EUV, X-ray or particles, or as inertial confinement fusion (ICF) drivers. On the other hand, the great advent of industrial lasers has been observed throughout recent years. This resulted in a renaissance of CO 2 laser systems, development of micro-lasers, high-average power fiber systems, and thin-disk lasers. Many of these systems became commercially available either as “off-the-shelf” or customized solutions tailored to a client’s specific requirements. The two trends present the generic flavor of the present laser market. This book gives a brief overview into how such systems are built, what physical phenomena they make use of, or even how to tune laser design for particular applications. Dr. Krzysztof Jakubczak Croma Polska Sp. z o.o. Warsaw Poland [...]... to produce chaotic output as indicated by Fig 11 14 Laser Systems for Applications crystal current I(t) laser power Pl(t) laser power PL(t) for SCPEM-off Fig 13 Pulse sequence of a SCPEM-Q-switched Nd:YAG -laser: pulse frequency 190.2kHz, average power 2.1W, peak power 70W, pulse width 333ns Crystal current I(t) (upper graph) and laser powers Pl(t) for SCPEM-on and SCPEM-off (with 2.8W cw-power) Fig... emission which travels in a direction that 10 Laser Systems for Applications contributes to the laser mode by ASE (amplified spontaneous emission) and is also responsible for the start of laser operation, tn…life time of the upper laser level, p = Pabs/Epp/Vg (Pabs…absorbed pumping power, Epp…pump photon energy, Vg…volume of gain medium) … pumping rate when the upper laser level is empty (number of excited... 3:7), and the peak power of this laser is 4750 W 24 Laser Systems for Applications Fig 6 Measurement shapes of the pulsed laser: (a) pulse width, (b) delay time (Ch1 is Laser pulse waveform; Ch2 is transistor-transistor logic trigger signal) A conclusion can be drawn by comparing figure 4 with figure 6 The measured results of peak power, pulse width and establishing time of laser pulse are in agreement... produced This parameter is of utmost importance in the laser rate equations describing the laser dynamics 3.2 The laser rate equations The simplest model to describe laser- activity is based on two coupled rate equations for the average population density n (of the upper laser level) and the average photon density P in the laser gain medium (see for an introduction e.g Siegmann, 1986)  P(t )   c ... pumping rate when the upper laser level becomes filled using nmax the number of laser active atoms per m³, nth…thermal excitation of the lower laser level (important for quasi-three level systems like Yb:YAG, where the lower laser level has little energetic distance to the ground level and is therefore filled in thermal equilibrium according to the Boltzmann-statistics), Γ … laser mode overlap factor... show that the peak power has a maximum when it changes with transmittance, which lays a theoretical foundation for the optimization of laser parameter 26 Laser Systems for Applications Fig 8 Light intensity in the laser cavity versus time at different transmittance Fig 9 Output power of the laser versus time at different transmittance According to the simulation results above, our laboratory has manufactured... (11) Where λ is the laser wavelength, υ0 is the laser frequency, ΔυL is the laser transition line width, ΔυN is the laser natural line width, τsp is the spontaneous emission rate, A is the cross section of the laser beam, F=l/L is the filling factor, l is the length of gain media When the Q-switch is closed, the loss in the cavity is so high that there is no laser output and the laser intensity in the... higher when the incident laser is linearly polarized light Under this condition, the performance of acousto-optically Q-switch is better This structure is propitious to realize linearly polarized laser output and reduce optical loss, which is helpful for laser output with Q-switch Fig 2 Schematic diagram of acousto-optically Q-switch CO2 laser 19 Acousto-Optically Q-Switched CO2 Laser The discharge tube... Q-switched CO2 laser 3.1 The six-temperature model for acousto-optically Q-switched CO2 laser Based on the theory of five-temperature model of the dynamics for CO2 laser (Manes & Seguin, 1972), the dissociating influence of CO2 to CO molecules on laser output is concerned Thus the equivalent vibrational temperature of the CO molecules is taken as a variable quantity of the differential equations for this... spontaneously emitted photon must go after on laser- mirror-reflection through the whole laser rod Hence M must be smaller than two 2 This formula for the mode factor is obtained by assuming a constant laser mode cross-section A along the resonator, equal to the cross-section A of the gain Further it must be considered that all generated photons are generated on the laser mode volume A more detailed calculation . LASER SYSTEMS FOR APPLICATIONS Edited by Krzysztof Jakubczak Laser Systems for Applications Edited by Krzysztof Jakubczak. Cr:Forsterite Lasers with One Nd:YAG Laser Pumping and Applications for Non-Destructive THz Inspection 119 Tadao Tanabe and Yutaka Oyama Part 2 Laser Beam Manipulation 137 Chapter 7 Laser. δ 1 = 4, δ 3 = 4/3 Laser Systems for Applications 10 contributes to the laser mode by ASE (amplified spontaneous emission) and is also responsible for the start of laser operation, t n …life