We present a detailed overview of stimulated Brillouin scattering (SBS) in
 single-mode optical fibers. The review is divided into two parts. In the first part,
 we discuss the fundamentals of SBS. A particular emphasis is given to analytical
 calculation of the backreflected power and SBS threshold (SBST) in optical fibers
 with various index profiles. For this, we consider acousto-optic interaction in the
 guiding geometry and derive the modal overlap integral, which describes the
 dependence of the Brillouin gain on the refractive index profile of the optical
 fiber. We analyze Stokes backreflected power initiated by thermal phonons, compare
 values of the SBST calculated from different approximations, and discuss the SBST
 dependence on the fiber length. We also review an analytical approach to calculate
 the gain of Brillouin fiber amplifiers (BFAs) in the regime of pump depletion. In the
 high-gain regime, fiber loss is a nonnegligible effect and needs to be accounted for
 along with the pump depletion. We provide an accurate analytic expression for the BFA
 gain and show results of experimental validation. Finally, we review methods to
 suppress SBS including index-controlled acoustic guiding or segmented fiber links.
 The second part of the review deals with recent advances in fiber-optic applications
 where SBS is a relevant effect. In particular, we discuss the impact of SBS on the
 radio-over-fiber technology, enhancement of the SBS efficiency in Raman-pumped
 fibers, slow light due to SBS and SBS-based optical delay lines, Brillouin
 fiber-optic sensors, and SBS mitigation in high-power fiber lasers, as well as SBS in
 multimode and microstructured fibers. A detailed derivation of evolutional equations
 in the guided wave geometry as well as key physical relations are given in
 appendices.

Stimulated Brillouin scattering in optical fibers

A display system for providing a two dimensional image includes an essentially one dimensional light valve array. The diffractive light valve array includes modulator elements which diffract or reflect light incident thereon to an extent determined by an image element to be represented. The display system is arranged such diffracted light from the light-valve array passes through a magnifying lens and is separated from the reflected light from the array. A magnified virtual image of the array formed by the diffracted light is viewed through the magnifying lens. A scanning arrangement between the viewer and the magnifying lens scans the image of the light-valve array across the field of view of the viewer sufficiently quickly that the viewer perceives the scanned image as a two-dimensional image. In another arrangement a printer is formed by scanning a real image of the diffractive light valve array over a printing or recording medium.

Display device incorporating one-dimensional grating light-valve array

In 1982, the first reports of laser ablation of polymers were issued almost simultaneously by Y. Kawamura et al.1 and R. Srinivasan et al.2 Srinivasan went on to become a leader in the field of polymer ablation. Srinivasan probably also coined the terms laser ablation and ablative photodecomposition, now in common use. The onset of material removal by laser ablation characteristically occurs at a well-defined laser fluence (energy per unit area). As the fluence is raised above this threshold, the ablation rate increases. The threshold fluence (F0 or Fth) is material and laser wavelength dependent and can vary from tens of mJ cm-2 to more than 1 J cm-2. The discovery of laser ablation of polymers sparked research in this field in many groups around the world. Many aspects of polymer ablation, and laser processing in general, are reviewed by Bauerle.3 Today, commercial applications of polymer laser ablation include the preparation of viaholes in polyimide for multichip modules at IBM4 and the production of inkjet printer nozzles (also polyimide).5 Considerable progress has been made in understanding polymer ablation since the last series of reviews a decade ago.6-8 New developments in polymer ablation include the application of femtosecond laser pulses, vacuum ultraviolet lasers (VUV), and free electron lasers (FEL). Some of these techniques have a great potential for the development of new applications and research tools. Much of this progress is discussed in this and other articles appearing in this special issue of Chemical Reviews. Current research on polymer ablation may be divided into two areas: (i) Applications of laser ablation, novel materials, and techniques. (ii) Studies of ablation mechanisms (databased modeling). The first area will be discussed in detail in this article, while the mechanistic aspects, especially the theoretical part, are discussed in other articles in this special issue. Many experimental methods and experimental polymers have been designed with a view toward improving our understanding of ablation mechanisms. It is often impossible to completely separate experiments designed to illuminate ablation mech† Paul Scherrer Institut. ‡ Washington State University. 453 Chem. Rev. 2003, 103, 453−485

/pdf/chemical-and-spectroscopic-aspects-of-polymer-ablation-sdd9ejfs8r.pdf

Chemical and spectroscopic aspects of polymer ablation: Special features and novel directions

Replacement of CH4 in the hydrate by use of liquid CO2

An overview is presented of experimental and theoretical research in the field of physics and engineering of singlet delta oxygen (SDO) production in low-temperature plasma of various electric discharges. Attention is paid mainly to the SDO production with SDO yield adequate for the development of an electric discharge oxygen–iodine laser (DOIL). The review comprises a historical sketch describing the main experimental results on SDO physics in low-temperature plasma obtained since the first detection of SDO in electric discharge in the 1950s and the first attempt to launch a DOIL in the 1970s up to the mid-1980s when several research groups started their activity aimed at DOIL development, stimulated by success in the development of a chemical oxygen–iodine laser (COIL). A detailed analysis of theoretical and experimental research on SDO production in electric discharge from the mid-1980s to the present, when the first DOIL has been launched, is given. Different kinetic models of oxygen low-temperature plasma are compared with the model developed by the authors. The latter comprises electron kinetics based on the accompanying solution of the electron Boltzmann equation, plasma chemistry including reactions of excited molecules and numerous ion–molecular reactions, thermal energy balance and electric circuit equation. The experimental part of the overview is focused on the experimental methods of SDO detection including experiments on the measurements of the Einstein coefficient for SDO transition and experimental procedures of SDO production in self-sustained and non-self-sustained discharges and analysis of different plasma-chemical processes occurring in oxygen low-temperature plasma which brings limitation to the maximum SDO yield and to the lifetime of the SDO in an electric discharge and its afterglow. Quite recently obtained results on gain and output characteristics of DOIL and some projects aimed at the development of high-power DOIL are discussed.

https://iopscience.iop.org/article/10.1088/0022-3727/40/2/R01/pdf

Physics and engineering of singlet delta oxygen production in low-temperature plasma

Computer models developed so far on electron‐beam‐excited KrF(B–X, 248 nm) lasers that include the vibrational relaxation process in the upper lasing B level at the finite rate could not predict the high intrinsic laser efficiency which was experimentally reported. This is attributed to the reduction of the laser extraction efficiency. We have developed a four‐level KrF laser model that includes the vibrational relaxation process and also the collisional mixing of the KrF*(B) and the KrF*(C) levels. The collisional quenching rates for KrF*(B,C) that we used and the vibrational relaxation rate were carefully estimated by using the effective spontaneous lifetimes for KrF*(B,C). As a result, the model prediction was in quite good agreement with many experimental results for a saturation behavior of KrF*(B–X) fluorescence, for small‐signal gains, for small‐signal absorptions, and for intrinsic efficiencies. Estimated rate constants in this model for the vibrational relaxation and the KrF*(B,C) mixing are 4×10...

An advanced kinetic model of electron‐beam‐excited KrF lasers including the vibrational relaxation in KrF*(B) and collisional mixing of KrF*(B,C)

Theoretical analysis of the discharge characteristics and the output performance of a self‐sustained discharge XeCl laser is described Validity of the theoretical laser model including the excitation circuitry is confirmed by comparing the results with the measured discharge and output performance under lasing conditions The dischare parameters such as E/P (E is the electrical field strength and P is the operating pressure) and discharge resistivity are theoretically studied for both Ne‐ and He‐based gas mixtures Our model shows that the electron energy distribution functions of these two mixtures become quite equal at each quasi‐steady‐state E/P, and that the improved laser output performance with Ne‐based gas mixtures is not due to the difference of the electron energy distribution function but due to the good optical extraction caused by the faster ion‐ion recombination excimer formation channel Moreover, the model also predicts that the depletion of HCl molecules is one of the most serious problem

Theoretical analysis of a self-sustained discharge pumped XeCl laser

The preionization characteristics of X-rays for self-sustained discharge rare-gas-halide lasers are summarized. X-rays showed features superior to UV for preionization of large volume high-pressure discharge lasers, which was experimentally confirmed. Futhermore, the effect of preionization on laser output was found to depend on the spatial distribution of preionization electron density and discharge electric field. When a uniform electric field area was homogeneously preionized with a collimated X-ray, an electron density of 107cm-3was found to be sufficient for high energy extraction of a XeCl laser.

X-ray preionization of rare-gas-halide lasers

We demonstrated the measurements of attenuation constant of a multi-mode fiber with 300-micron core diameter and 1-km length at 1070 nm. The observed attenuation constant was below 0.7 dB/km, the laser power of 5 kW was coupled into the 1-km fiber at 1070 nm, and the overall transmittance was 85%, and the first Raman Stokes signal was observed in the transmitted laser spectrum. We demonstrated concrete cutting with a 4-kW fiber laser at 1070 nm. The slab thickness was 100 mm. This technique can be extended to thick concrete slabs more than 1 m without increasing laser power.

Laser cutting for thick concrete by multi-pass technique

As a novel alternative to existing means of preionization, we have used x radiation to preionize a high‐pressure KrF laser mixture and found that the x‐ray preionization produces a uniform glow discharge for high‐pressure KrF laser gas.

Tomoo Fujioka

Papers

An advanced kinetic model of electron‐beam‐excited KrF lasers including the vibrational relaxation in KrF(B) and collisional mixing of KrF(B,C)

Theoretical analysis of a self-sustained discharge pumped XeCl laser

X-ray preionization of rare-gas-halide lasers

Laser cutting for thick concrete by multi-pass technique

X‐ray‐preionized high‐pressure KrF laser