Investigation On Characteristics Of Frequency Doubling In One-dimensional BBO Photonic Crystals

Photonic crystal is a kind of inhomogeneous artificial electromagnetic mediumwhich dielectric constant is periodical distribution. It has forbidden band and Braggreflection and transmission enhancement feature so its nonlinear effect is strongerthan other nonlinear homogeneous medium. At the same time, with the developmentof integrated optics and WDM technology in communication, nonlinear photoniccrystals becoming the focus of a large study. So the frequency doubling properties ofphotonic crystals are very meaningful.Firstly, this dissertation briefly summarizes the basic concept and the domesticand abroad research progress of photonic crystals. Then the transfer characteristicmatrix of one-dimensional photonic crystal is derived using the transfer matrixmethod, the expressions of transmittance and effective refractive index of the one-dimensional photonic crystal are obtained. Secondly, frequency doubling in a one-dimensional nonlinear photonic crystal is studied under the undepleted pumpapproximation. A general expression of second harmonic field is derived byintroducing the phase mismatch factor, where the operation of matrices involved issimplified. Thirdly, in the case of angle detuning, the second harmonic generation issimulated in a BBO nonlinear photonic crystal model. Through the curve offrequency doubling conversion efficiency, the variation of the conversion efficiencywith the number of layers is analyzed. And then it obtains the relationships betweenfrequency doubling conversion efficiency and the effective refractive indexdifference and the transmittance respectively. Finally, by adjusting parameters ofmaterial and structure of one-dimensional nonlinear photonic crystals can make thefundamental and harmonic waves are located at any resonance peak of the forbiddenband edge respectively, then it calculates the short pulse conversion efficiency underthis case. Through comparison study it is found that due to phase modulationcharacteristics of Bragg reflection, the phase matching for bulk BBO crystals is no longer suitable for photonic crystals. When the photonic crystal transmittance is thelargest and effective refractive index matching, the conversion efficiency is thelargest. The more close to the edge of the forbidden band resonance peak, the greaterthe conversion efficiency.