Have you ever felt that the very title, Progress in Optics, conjured an image in your mind? Don’t you see a row of handsomely printed books, bearing the editorial stamp of one of the most brilliant members of the optics community, and chronicling the field of optics since the invention of the laser? If so, you are certain to move the bookend to make room for Volume 16, the latest of this series. It contains seven chapters on widely diverging topics, written by well-known authorities in their fields. These are: 1) Laser Selective Photophysics and Photochemistry by V. S. Letokhov, 2) Recent Advances in Phase Profiles (sic) Generation by J. J. Clair and C. I. Abitbol, 3 ) Computer-Generated Holograms: Techniques and Applications by W.-H. Lee, 4) Speckle Interferometry by A. E. Ennos, 5 ) Deformation  Invariant, Space-Variant Optical  Pattern Recognition by D. Casasent and D. Psaltis, 6) Light Emission from High-Current Surface-Spark Discharges by R. E. Beverly, and 7) Semiclassical Radiation  Theory within a  QuantumMechanical Framework by I. R. Senitzkt. The  breadth of topic  matter  spanned  by  these  chapters makes it impossible, for this reviewer at least, to pass judgement on the comprehensiveness, relevance, and completeness of every chapter. With an editorial board as prominent as that of Progress in Optics, however, it seems hardly likely that such comments should be necessary. It should certainly be possible to take the authority of each author as credible. The only remaining judgment to be  made on these chapters is their readability. In short, what are they like to read? The first sentence of the first chapter greets the eye with an obvious typographical error: “The creation of coherent laser light source, that have tunable radiation, opened the . . . .” Two pages later we find: “When two types of atoms or molecules of different isotopic composition ( A and B ) have even one spectral line that does not overlap with others, it is pos-

Progress in optics

In this paper, we summarize the fundamental properties and review the latest developments in high power fiber lasers. The review is focused primarily on the most common fiber laser configurations and the associated cladding pumping issues. Special attention is placed on pump combination techniques and the parameters that affect the brightness enhancement observed in single-mode and multimode high power fiber lasers. The review includes the major limitations imposed by fiber nonlinearities and other parasitic effects, such as optical damage, transverse modal instabilities and photodarkening. Finally, the paper summarizes the power evolution in continuous-wave and pulsed ytterbium-doped fiber lasers and their impact on industrial applications.

High Power Fiber Lasers: A Review

Microwave photonics (MWP) is an emerging field in which radio frequency (RF) signals are generated, distributed, processed and analyzed using the strength of photonic techniques. It is a technology that enables various functionalities which are not feasible to achieve only in the microwave domain. A particular aspect that recently gains significant interests is the use of photonic integrated circuit (PIC) technology in the MWP field for enhanced functionalities and robustness as well as the reduction of size, weight, cost and power consumption. This article reviews the recent advances in this emerging field which is dubbed as integrated microwave photonics. Key integrated MWP technologies are reviewed and the prospective of the field is discussed.

Integrated microwave photonics

In the 2015 review paper 'Petawatt Class Lasers Worldwide' a comprehensive overview of the current status of highpower facilities of >200 TW was presented. This was largely based on facility specifications, with some description of their uses, for instance in fundamental ultra-high-intensity interactions, secondary source generation, and inertial confinement fusion (ICF). With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification (CPA), which made these lasers possible, we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed. We are now in the era of multi-petawatt facilities coming online, with 100 PW lasers being proposed and even under construction. In addition to this there is a pull towards development of industrial and multidisciplinary applications, which demands much higher repetition rates, delivering high-average powers with higher efficiencies and the use of alternative wavelengths: mid-IR facilities. So apart from a comprehensive update of the current global status, we want to look at what technologies are to be deployed to get to these new regimes, and some of the critical issues facing their development.

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Petawatt and exawatt class lasers worldwide

Recent advances in photonic integration have propelled microwave photonic technologies to new heights. The ability to interface hybrid material platforms to enhance light–matter interactions has led to the development of ultra-small and high-bandwidth electro-optic modulators, low-noise frequency synthesizers and chip signal processors with orders-of-magnitude enhanced spectral resolution. On the other hand, the maturity of high-volume semiconductor processing has finally enabled the complete integration of light sources, modulators and detectors in a single microwave photonic processor chip and has ushered the creation of a complex signal processor with multifunctionality and reconfigurability similar to electronic devices. Here, we review these recent advances and discuss the impact of these new frontiers for short- and long-term applications in communications and information processing. We also take a look at the future perspectives at the intersection of integrated microwave photonics and other fields including quantum and neuromorphic photonics. This Review discusses recent advances of microwave photonic technologies and their applications in communications and information processing, as well as their potential implementations in quantum and neuromorphic photonics.

Fiber lasers provide an attractive means of reaching high output laser power because of their advantages in terms of compactness, reliability, efficiency, and beam quality. Even given these advantages, it is desirable to increase the system power or energy levels beyond what is possible with a single-mode fiber laser. A promising technique is coherent beam combining with active phase locking involving phase detection and active compensation of phase errors [1]. In this Communication, we present coherent phase combining of 64 independent fibers, selectively amplified by 4 optical amplifiers. This is to our knowledge the highest number of combined fibers ever demonstrated. In order to achieve this result, we have developed specific collective components for phase measurement of a large number of fibers, arrays of phase modulators, and an array of collimated fibers.

Coherent phase combining of 64 fibers

We present the 2 and 4 taps SOI coherent MWP filter devices. The 2 tap unit cell is characterized and shows tap delay tunability and optical phase control thanks to on-chip photodiodes. An optical phase lock loop is successfully implemented for filter stabilization.

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Silicon-on-insulator photonic crystal multi-tap microwave photonics filter

Tiled-aperture Coherent Beam Combination architecture opens the way to digital laser operating in high peak and
average power regimes.

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61 channels coherent beam combining femtosecond digital laser

L'invention a pour objet un systeme d'imagerie polarimetrique presentant un axe optique, et comprenant des moyens de detection et d'analyse (35) de la lumiere retro-diffusee par un objet illumine par une source de lumiere et au moins une lame d'onde programmable (33) caracterise en ce que la lame d'onde programmable comprend un materiau avec un tenseur electro-optique isotrope et un jeu d'au moins trois electrodes disposees selon des directions paralleles a l'axe optique du systeme d'imagerie.

Systeme d'imagerie polarimetrique a matrice de lames d'onde programmables a base de materiau avec un tenseur electro-optique isotrope

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Jérôme Bourderionnet

Papers

Coherent phase combining of 64 fibers

Silicon-on-insulator photonic crystal multi-tap microwave photonics filter

61 channels coherent beam combining femtosecond digital laser

Systeme d'imagerie polarimetrique a matrice de lames d'onde programmables a base de materiau avec un tenseur electro-optique isotrope

Optical Phase-Locked Loop Phase Noise in 5g Mm-Wave Ofdm Arof Systems