Harmonic Generation Applications Research Articles

Novel concepts for improved nonlinear transmission line performance

Three new device concepts have been investigated to improve the performance of nonlinear transmission lines (NLTL's). These devices, the multi-quantum barrier varactor, the Schottky quantum barrier varactor, and the Schottky superlattice quantum barrier varactor, are predicted to offer significant advantages over the conventional Schottky varactor because of their stronger C-V nonlinearities, symmetric C-V characteristics, high cutoff frequency and increased breakdown voltages. The wave evolution on an NLTL has been numerically investigated using an improved model in which the effects of skin losses, line parasitics and device leakage current have been included. A new transmission line layout design, which permits one to double and even triple the voltage handling capability of the NLTL (dependent upon the minimum pulse duration requirements), with a back-to-back device configuration, enables both positive and negative voltage waveforms to be efficiently compressed. These new devices are shown to be useful in high power harmonic generation applications as well. >

Applications of harmonic generation of picosecond pulses from a free electron laser

Using nonlinear crystals we have produced harmonics of the Mark III infrared free electron laser at wavelengths from 495 nm to .1 μm. Optimization of energy conversion efficiency as a function of temporal walkoff, Poynting-vector walkoff, finite line width and length will be discussed. Preliminary results on an optimized coated crystal system will be presented and compared to theory.

Polar Langmuir-Blodgett thin film layers for non-linear optical and pyroelectric applications

Abstract Advances in the synthesis of non-centrosymmetric molecules coupled with the recently acquired ability to incorporate them into stable three dimensional arrays with a high degree of order, holds out exciting possibilities for the development of high quality, low cost organic materials for a variety of applications. Langmuir-Blodgett (LB) films possessing a unique polar axis can be fabricated by depositing head to tail sequences of a specially designed molecule or better still by forming organic superlattices (alternate layers of different molecules) using purpose built equipment. Two device areas of particular interest that capitalize on this ability to form supermolecular assemblies are optoelectronics and pyroelectricity. This paper reviews the efforts that have been made in engineering molecules so as to optimize their non-linear properties. In the optics field, most attention has been placed on materials designed specifically for second harmonic generation applications. For thermal imaging pur...

Non-centrosymmetry in organic crystals: a study of molecular conformation in some substituted tolans

Unsymmetrically substituted tolans with moderate dipole moments are likely to adopt non-planar, chiral conformations in the solid state and non-centrosymmetric space groups, rendering them useful for second harmonic generation applications.

A proposed harmonic generator based on cyclotron waves

A cyclotron wave on a rectilinear filamentary beam can interact with a TE circuit mode of cylindrical symmetry propagating in synchronism with the beam. The interaction results in a periodic variation of the cyclotron transit angle of the electrons, causing a type of circumferential bunching which gives rise to high harmonic content. Provided the RF-field is adjusted to maximize a certain harmonic, its output power increases approximately as the square root of the harmonic number. The bunching is simply a redistribution of the relative positions of the various electrons constituting the original beam, and requires no supply of energy. All power delivered by the generator is therefore dissipated in the RF structure itself. The interaction mechanism is analyzed in detail, using two different approaches leading to the same final results. One is based on a wave description, the other considers the motion of the individual electrons. Possible applications for harmonic generation of high frequencies are discussed.