Pump Requirements for Parametric Amplification and Generation of Surface Waves on YZ LiNbO3
Absfract-Expressions are developed for estimating the threshold electric fields required for parametric amplification or generation of surface waves in piezoelectric materials utilizing the nonlinear characteristics of the material. When applied to Y Z LiNbOa, they yield values in excess of 20 kV/cm under the most optimistic, yet still realistic, conditions. These values are too Iarge for amplification or generation to be considered for practical applications. Several pump electrode geometries and circuit matching techniques were investigated to determine the best obtainable pump circuit performance. An interdigital electrode separated from the crystal by a small gap was found to be the most efficient pump electrode geometry and was capable of producing approximately ZkV/cm of field per watt’‘2 of input pump power.
A frequency-selective limiter using magnetoelastic instability
A new device which accomplishes frequency-selective limiting through parallel pumping of subharmonic magnetoelastic waves in YIG is introduced. In addition, the general requirements for any frequency-selective parametric limiter are discussed and shown to be applicable to the magnetoelastic limiter as well as the more conventional spin wave limiter (YIG or ferrite limiter). These general requirements may now be used as guides for developing other frequency-selective parametric limiters.
Dielectric Parametric Amplifier
Gain conditions are obtained for a microwave parametric amplifier in which the resonant structure is filled with a nonlinear dielectric material. The gain equation is applied to the case of a toroidal resonator of strontium titanate dielectric. At a signal frequency of 10 Gc/sec, the gain threshold is at a pump power of 7.5 W. If efficient energy transfer is to be realized between pump and signal, resonant modes of the dielectric amplifier must be chosen appropriately. The necessary conditions on mode geometry have been illustrated.