Cherenkov-type Phase Matching Research Articles

Visible light generation in the cladding of optical fibers carrying near-infrared continuous-wave lasers due to Cherenkov-phase matched harmonic conversion.

In this work, we report and analyze the cause of the surprising observation of visible light generation in the cladding of silica-based continuous-wave (CW), near-infrared fiber lasers. We observe a visible rainbow of hues in a cascaded Raman fiber laser, which we attribute to second and third harmonic conversion of the different wavelength components propagating in the core of the fiber. The light in the cladding of the fiber occurs through Cherenkov-type phase matching, and a mathematical analysis is presented to estimate the power of the harmonic light generated. We then extend this theory to visible light generation in other types of fiber lasers. Specifically, we analyze the case of a CW supercontinuum generated in standard telecom fibers, and verify our theoretical predictions with experimental results through visible spectra collected.

SINGLE DOMAIN WALL EFFECT ON PARAMETRIC PROCESSES VIA CHERENKOV-TYPE PHASE MATCHING

We report on a new character of single domain wall (DW) of electrically-poled ferroelectric crystal which can modulate parametric processes via Cherenkov-type phase matching. Experimental result shows that the effective nonlinear polarization is confined in DW, and its phase velocity can be modulated when incident light is off the domain wall's direction. These effects lead to novel Cherenkov second harmonic generation (CSHG), and other modulated parametric process, such as Cherenkov sum frequency generation (CSFG).

Cherenkov-type phase matching in bulk KDP crystal

The conical second harmonic emission from a bulk KDP crystal was detected and interpreted in terms of Cherenkov-type phase matching. In contrast to the models describing conical emission from a dense atomic medium, the present model is simple, independent of the intensity of pump and generated radiation and does not require including additional nonlinear effects, such as self-focusing and self-trapping. The experimentally registered parameters are in good agreement with theoretical data. The differences between Cherenkov-type phase matching and Cherenkov-type emission are discussed.

特集 超薄膜の構造と機能 有機高分子非線形光学材料：最近のトピックス

The present review is mainly concerned with the macromolecular organic nonlinear optical materials for frequency doubling. Organic polymer materials are expected to apply the optical devices for the transparent, easy processability and so on. Recently some studies were carring out about the polymer, chromophore and device structures. These topics are introduced in this review. One of the major problems for poled polymer systems is the lack of thermal stability after aligningchromophore units. In order to prevent the decay, some ferroelectric or crosslinkable polymers carrying chromophore moiety were prepared. They showed large d coefficients and stability. Previously, the chromophores having shorter absorption wavelength band than the harmonic wavelength have been used. However, it has made possible to apply the longer absorption wavelength chromophores by using Cherenkov type phase matching. Besides, it has reported that the novel two-directional charge transfer molecules possessed large off-diagonal, β components has shown a small decay of d 33 even when the order parameter has relaxed. In optical waveguide structure, quasi phase matching accomplished by periodically poled or bleached waveguide structure was effective method to obtain harmonic light. As the practical and adroid method to achieve phase matching in waveguide, a attempt was made to adjust and suppress the phase matching condition by continuing to apply external dc voltage during frequency doubling. The guide-layer made of low Tg polymer was effective for quick response of chromophore alignment and change of refractive index against external electric field.