Nonlinear Optics

Abstract

Coherence tomo- and topography have great potential in the building of optical measuring tools for a lot of different technical and biological applications. One major limiting property of scanning coherence methods is their data acquisition time. In this paper we describe two methods for increasing the measuring speed; one for an analogue and one for a digital preprocessing sensor. In particular, we present a novel scanning device for an analogue 1-D sensor which enables measurements with a very fast vertical scanning rate to be made. A periodical change of the optical path difference of up to 3 mm and frequencies of 1200 Hz and more can be achieved by using a resonant scanner. We describe an optical fibre setup using this novel scanner in combination with a homemade low cost light source which is most appropriate for optical fibre coherence application.     

Solid Hydrogen for Nonlinear Optics

We recently developed a new method of preparing a parahydrogen crystal which is suitable for experiments on nonlinear optical processes. The crystal was grown slowly from pressurized liquid–phase in order to avoid internal stress from the thermal constriction, and was cooled down to 4.2 K. The obtained crystal was uncracked and perfectly transparent with a high damage threshold. To evaluate the quality, the vibrational coherence decay was measured using the time–resolved coherent anti–Stokes Raman spectroscopy (CARS) technique. The decay process showed a nonexponential behavior, with an asymptotic limit characterized by a single time constant of 2.6 s, which corresponds to a linewidth of less than 0.1 MHz. This decay time is extremely slow compared to the previously published work.     

Halide Perovskites for Nonlinear Optics

Halide perovskites provide an ideal platform for engineering highly promising semiconductor materials for a wide range of applications in optoelectronic devices, such as photovoltaics, light-emitting diodes, photodetectors, and lasers. More recently, increasing research efforts have been directed toward the nonlinear optical properties of halide perovskites because of their unique chemical and electronic properties, which are of crucial importance for advancing their applications in next-generation photonic devices. Here, the current state of the art in the field of nonlinear optics (NLO) in halide perovskite materials is reviewed. Halide perovskites are categorized into hybrid organic/inorganic and pure inorganic ones, and their second-, third-, and higher-order NLO properties are summarized. The performance of halide perovskite materials in NLO devices such as upconversion lasers and ultrafast laser modulators is analyzed. Several potential perspectives and research directions of these promising materials for nonlinear optics are presented.     

Functional Dendrimers for Nonlinear Optics

Novel nonlinear optical (NLO) building blocks can be placed into the periphery, branch, or core of a dendrimer to construct precise molecular architecture with predetermined chemical composition. The site‐isolation effect, through the encapsulation of active moieties by dendrons, or the cooperative effect, through the coherent interaction among the same or different kinds of active blocks in the dendrimer, can greatly enhance the performance of NLO materials. This paper provides a review of recent developments in dendrimers for NLO applications, such as electro‐optics (E‐O), photorefractive (PR) materials, second harmonic generation (SHG), and two‐photon absorption (TPA).     

Organic Materials for Third-Order Nonlinear Optics

The current status of organic low-molecular weight and polymeric materials for third-order nonlinear optics is reviewed. The importance of organic materials lies in their promise of large nonlinear optical figure of merit, high optical damage thresholds, ultrafast optical responses, architectural flexibility, and ease of fabrication. Organic materials exhibiting interesting third-order nonlinear optical properties are discussed to illustrate the importance of structure–property correlations. Results on emerging organic materials that include liquids, dyes, fullerenes, charge-transfer complexes, π-conjugated polymers, dye-grafted polymers, organometallic compounds, composites, and liquid crystals are presented. Organic nonlinear optical materials seem promising for a wide range of applications and their potential for integrated optics should be further explored.     

有机吡啶盐分子在非线性光学领域中的应用

本文从分子工程和材料工程的角度介绍了有机吡啶盐及其衍生物在非线性光学中的应用。有机吡啶盐分子由于独特的化学结构,除了具有较大的分子超极化率外,其分子设计上的灵活性和功能上的多样性,使其在非线性光学材料领域占有重要的一筑之地。同时该类体系多种多样的组装形式也极大地丰富了非线性光学材料的种类。