Fiber Optic Tutorials

This is a continuation from the previous tutorial - optical frequency converters. In a nonlinear optical modulator, the modulation of an optical wave is accomplished through a nonlinear optical process. A nonlinear optical modulator can be based on either self modulation or cross modulation. In the case of self modulation, only one optical beam is present, and the modulation on the beam is a function of the characteristics of the beam itself. In the case of cross modulation, two or more optical beams are present, and the beam of interest is modulated by one or more other beams that carry...

This is a continuation from the previous tutorial - phase matching for nonlinear optical processes. A very important class of nonlinear optical devices is the optical frequency converters. Nonlinear optical frequency conversion is the only means for direct conversion of optical energy from one frequency to another. Indeed, the discipline of nonlinear optics was born out of the first observation of second-harmonic generation in 1961. There are basically two types of nonlinear optical frequency converters. The majority are based on parametric processes, particularly the parametric second-order processes, that require phase matching. Sum-frequency generators, difference-frequency generators, harmonic generators, and parametric amplifiers...

This is a continuation from the previous tutorial - coupled-wave analysis of nonlinear optical interactions. We have seen in the preceding tutorial the importance of phase matching for parametric nonlinear processes. If a parametric interaction is phase matched, optical power can be converted efficiently from one frequency to another. Otherwise, the process is periodically reversed, and the optical power shuttles back and forth among the interacting waves, as shown in Figure (9-8)(c) [refer to the coupled-wave analysis of nonlinear optical interactions tutorial]. No matter how long the crystal is, the best efficiency we can expect from a parametric interaction that...

This is a continuation from the previous tutorial - nonlinear optical interactions. The coupled-wave theory developed in the coupled-wave theory tutorial is used for analysis of nonlinear optical interactions in a homogeneous medium. In nonlinear optical waveguides, coupled-mode theory can be used if there is no mixing between different optical frequencies, but a combination of coupled-wave and coupled-mode formalisms has to be used if there is frequency mixing in the interaction. In applying coupled-wave or coupled-mode theory to the analysis of a nonlinear interaction, the perturbing polarization, generally expressed as \(\Delta\mathbf{P}\) in the coupled-wave theory tutorial, is identified as the characteristic...

This is a continuation from the previous tutorial - nonlinear optical susceptibilities. Optical susceptibilities in the frequency domain are, in general, complex quantities. Following the same convention, used in the linear optical susceptibility tutorial and the material dispersion tutorial for complex linear susceptibility in the frequency domain, complex nonlinear susceptibilities in the frequency domain can be expressed as \(\boldsymbol{\chi}^{(2)}=\boldsymbol{\chi}^{(2)'}+\text{i}\boldsymbol{\chi}^{(2)''}\) and \(\boldsymbol{\chi}^{(3)}=\boldsymbol{\chi}^{(3)'}+\text{i}\boldsymbol{\chi}^{(3)''}\) to define their real and imaginary parts clearly. Similarly to the case of linear susceptibility discussed in the material dispersion tutorial, the imaginary part of a nonlinear susceptibility is always associated with the intrinsic resonances of a material. Such resonances signify...