Cerenkov-type Second-harmonic Generation Research Articles

Theoretical study on the Cerenkov-type second-harmonic generation in optical superlattices without paraxial approximation.

In this paper, the Cerenkov-type second-harmonic generation in bulk optical superlattices has been studied theoretically with the non-paraxial wave equations, where the paraxial approximation is avoided. The corresponding phase-matching condition is determined strictly by solving the non-paraxial wave equations under proper boundary conditions, and the result coincides well with the traditional Cerenkov phase-matching condition. In addition, a backward Cerenkov phase-matching condition is deduced from the wave equations as well, and the physical requirement of this condition is clarified.

Theoretical analysis of electromagnetic field distribution and Cerenkov second harmonic generation conversion efficiency based on lithium niobate ion-implanted channel waveguide

Cerenkov type second harmonic generation (CSHG) is proposed in ion-implanted Z-cut lithium niobate (LiNbO3) channel waveguides. We have obtained exact analytical solutions for the field distribution and the power of second-harmonic waves. Conditions for attaining higher conversion efficiency are discussed on the basis of numerical calculations.

Cerenkov-Type Second-Harmonic Generation in Two-Dimensional Nonlinear Photonic Structures

We study the Cerenkov-type second-harmonic generation in several different two-dimensional nonlinear photonic structures formed in birefringent crystals with the 3 m symmetry. Depending on the degree of birefringence, we observe either single or double Cerenkov-like second-harmonic rings. We discuss the properties of these parametrically generated rings and show that their sixfold azimuthal modulation is associated with the hexagonal symmetry of the individual ferroelectric domains.

Blue Light Generation by Cerenkov-type Second-Harmonic Generation in Thermally Poled Silicate Glass Thin Film Waveguide

We observe a second-order nonlinearity of poled Ge-doped silica thin film. The origin of nonlinearity and the stability of the nonlinearity against heat and intense laser light are investigated from poled glass thin film. We fabricate a frequency doubling device using the silicate thin film waveguide, and by Cerenkov-type frequency doubling blue light generation was realized.

Cerenkov-type second-harmonic generation in KNbO/sub 3/ channel waveguides

Cerenkov-type second-harmonic generation using KNbO/sub 3/ channel waveguides produced by MeV He/sup +/-ion implantation is presented from the viewpoint of device design. We derive the Cerenkov phase-matching condition for multimode waveguides and utilize Cerenkov-angle analysis as a tool for contact-free measurement of the effective indexes of guided modes of ion-implanted KNbO/sub 3/ channel waveguides at a wavelength of 860 nm. The measured mode indexes are in full agreement with calculations based on the effective-index method and the refractive index-depth profiles of ion-implanted KNbO/sub 3/ waveguides. The efficiency of Cerenkov-type second-harmonic generation is modeled using analytical approximations of the field distributions of the fundamental and the Cerenkov-radiation modes in embedded-channel waveguides. The acceptance width for Cerenkov-type frequency doubling in these ion-implanted waveguides is about one order of magnitude wider than for noncritical phase-matched second-harmonic generation in bulk KNbO/sub 3/ crystals. Based on the theoretical simulations, guidelines for optimum device design are given, and the possibility to increase the ultimate conversion efficiency to about 30% W/sup -1/ cm/sup -1/ through lateral-resonance enhancement of the second-harmonic field in KNbO/sub 3/ channel waveguides is demonstrated.

CERENKOV-TYPE OPTICAL SECOND-HARMONIC GENERATION IN ORGANIC-CRYSTALLINE CHANNEL WAVEGUIDES

Cerenkov-type optical second-harmonic generation (SHG) in organic-crystalline waveguides has been investgated. Various techniques for the fabrication of organic-crystalline waveguides are described. Planar and channel waveguides have been fabricated using an organic nonlinear optical crystal (−)2-(α-methylbenzylamino)-5-nitropyridine (MBANP). Visible blue light has been obtained in an MBANP rib waveguide using a laser-diode source. Theoretical analysis of Cerenkov-type SHG in planar waveguides is made, and a simple analytic expression for second-harmonic power is derived. Optimum conditions for attaining high conversion efficiency are discussed on the basis of the theoretical calculations.

Theoretical analysis of Cerenkov-type optical second-harmonic generation in slab waveguides

Optical second-harmonic generation in the Cerenkov-radiation scheme in slab waveguides has been theoretically investigated for all the possible type I configurations. By solving the nonlinear wave equations analytically, a simple general expression for the second-harmonic power has been obtained. Characteristics of the Cerenkov-type second-harmonic generation and optimum conditions for attaining high conversion efficiencies are discussed on the basis of the theoretical analysis. It is shown that, in order to attain high conversion efficiencies, off-diagonal elements of the nonlinear optical coefficient tensor should be utilized taking advantage of birefringence. >

Second-harmonic generation by Cerenkov-type phase matching in a poled polymer waveguide

A copolymer of methyl methacrylate and azo-dye-substituted methacrylate is corona-poled. Cerenkov-type second-harmonic generation (SHG) of Nd:YAG laser is observed in the poled polymer waveguide even though there is strong absorption of the SHG wavelength. The total SHG conversion efficiency is 1.72 × 10−3%, and the net SHG conversion efficiency in the waveguide is 0.21%.

Grating axicon for collimating Čerenkov radiation waves

An axicon optical element that utilizes a diffraction grating has been fabricated for collimating the Cerenkov radiation wave. The grating axicon has the advantage of a simple structure, which can easily be fabricated by the computerized numerical control machining technique. The collimation function of the grating axicon is confirmed for Cerenkov-type second-harmonic generation in LiNbO(3) waveguides, and correction of the aberration caused by substrate anisotropy is investigated. The aberration can be compensated by appropriately inclining either the substrate facet or the grating axicon.