Fiber Optic Tutorials
Raman and Brillouin Devices
This is a continuation from the previous tutorial - bistable optical devices. The nonparametric processes of stimulated Raman scattering and stimulated Brillouin scattering both cause a shift of the optical frequency, leading to a loss for the pump beam and a gain for a Stokes beam if the material is not originally excited or a gain for an anti-Stokes beam if it is excited. On the positive side, such processes can be utilized for optical frequency conversion and optical signal amplification. On the negative side, however, they also place some serious limitations on the performance of certain optical devices and...
Bistable optical devices
This is a continuation from the previous tutorial - nonlinear optical modulators and switches. A bistable device has two stable output states under one input condition. Because of this binary feature, bistable devices can be used for many digital operations, such as switches, memories, registers, and flip-flops. Bistable electronic circuits and devices have become indispensable components in a wide range of application that require the storage of binary information. Bistable optical devices can be important for their applications as optical logic, memories, and analog-to-digital converters in optical signal processing systems. In addition, they can also be used as optical pulse...
Nonlinear Optical Modulators and Switches
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...
Optical Frequency Converters
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...
Phase Matching for Nonlinear Optical Processes
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...