Laser & Photonics Reviews

Light storage in a highly birefringent optical fibre through the intercession of an acoustic vibration in the medium. The stored signal interacts with a writing pulse through stimulated Brillouin scattering to create an acoustic wave replicating the signal waveform as a vibration in the material. The signal can be faithfully retrieved a moment later in the orthogonal polarization using a read pulse that is reflected on the grating generated by the acoustic vibration. Picture: S. Chin, L. Thévenaz, pp. 724 – 738, in this issue)

The use of ultrashort laser pulses for fiber grating inscription has many advantages in comparison to continuous-wave and long-pulse lasers. The most important one is that it allows inscription in nonphotosensitive fiber materials. In this article the principal inscription techniques and the physical properties of femtosecond (fs) pulse written in-fiber gratings are reviewed. The role of focusing and order walk-off on the inscribed structures is emphasized. Selected applications of such gratings for sensing and fiber lasers are discussed.

A comprehensive overview is presented about optical fiber-based tunable photonic delay lines, which have been steadily developed over the last decade for the realization of all-optically controlled timing functions. The most widely used techniques, such as those based on slow & fast light and wavelength conversion associated to dispersion, are described and their physical limitations are discussed in terms of the maximal achievable delay, the associated signal distortion and signal bandwidth.

In this article it will be shown that intensive laser radiation is a perfect tool for processing of diamond materials: single crystal, poly- and nanocrystalline diamond, amorphous diamond-like coatings, micro- and nanoparticles. The method of synthesis and the major properties of these materials, such as optical absorption and thermal conductivity, will be briefly reviewed. Emphasis is placed on the mechanisms and general futures of laser-induced surface and bulk graphitization of diamond.

It is widely recognized that nonradiative quenching of excitons by other excitons and polarons become the dominant decay mechanism of these excitons at high excitation densities. These quenching processes cause the roll-off in the efficiency of organic light-emitting devices (OLEDs) and prevent lasing at high injection current densities. This review presents the optically-detected magnetic resonance (ODMR) evidence for these photoluminescence- and electroluminescence-quenching processes.

The nanoscale structure of femtosecond laser-induced modifications known as “nanogratings” has been the subject of speculation and intensive debate throughout the decade since their discovery. The aim of this work is to gain dependable information on the three-dimensional (3D) substructure of nanogratings down to the nanometre scale.

In this article the promise of on-chip diamond ring resonators for wavelength conversion based on Kerr and Raman-resonant four-wave mixing is numerically demonstrated. After examining to what extent both dispersion-engineered phase-matching and “automatic” quasi-phase-matching can be established in diamond ring converters, it is shown that such a “double-matching” approach can yield high conversion efficiencies for a wide range of wavelengths in the near-infrared/mid-infrared domain, as well as in the ultraviolet/visible domain.

Two common methods for recording absolute photoluminescence quantum yields using integrating spheres are discussed. These methods are developed from a theoretical standpoint. The assumptions made for each method are discussed, and practical comparisons between the two are made using a range of different materials and sample types. It is shown that despite the underlying theoretical differences both methods ultimately yield very similar experimental results.

The propagation of defect networks in failed 980 nm emitting high-power diode lasers is analyzed. This is accomplished ex post facto by electron-beam based techniques applied without device preparation and in situ by thermographic microscopy with 1 μs time resolution. Moreover, an iterative model is established, which allows for describing both the shape of the observed defect networks as well as the kinetics of their spread. This concerted approach allows the clear assignment of starting points of extended defect systems as well as analysis of their evolution kinetics.

Experimental demonstration of semiconductor saturable absorber-free mode-locked optically pumped semiconductor disk laser is presented. The origin of pulsed operation is attributed to the intensity dependent Kerr lens effect arising in the semiconductor gain medium. Achieved results represent a novel method to mode-lock this type of laser opening new application opportunities.