Responsivity optimization in magneto-optic sensors based on ferromagnetic materials.

In an effort to optimize magnetic field detection sensitivities, the Faraday responsivity vector, which determines the relationship between the Faraday rotation angle and an externally applied magnetic field, was investigated in magneto-optic sensors based on bismuth-doped iron-garnet films. Under externally applied fields, Faraday rotation is produced principally by domain rotation and domain wall motion, whose relative contributions depend on the domain geometry and the direction of laser propagation. When optically probed along a principal magnetization axis, Faraday rotation is driven by a single magnetization mechanism, and the responsivity is linearized (reduced to an effective Verdet constant).

Optimal crystal geometry and orientation in electric field sensing using electro-optic sensors.

For optimal sensitivity in electric field measurements, electro-optic (EO) crystals are typically selected based on their EO coefficients and dielectric constants. However, the conventional figure of merit yields sensitivity predictions regarding EO materials that are inconsistent with experimental data. In this Letter, we demonstrate that depolarization effects, which are often ignored, can dramatically enhance responsivity depending on the shape and orientation of the EO crystal.

Chaos regularization of quantum tunneling rates.

Quantum tunneling rates through a barrier separating two-dimensional, symmetric, double-well potentials are shown to depend on the classical dynamics of the billiard trajectories in each well and, hence, on the shape of the wells. For shapes that lead to regular (integrable) classical dynamics the tunneling rates fluctuate greatly with eigenenergies of the states sometimes by over two orders of magnitude. Contrarily, shapes that lead to completely chaotic trajectories lead to tunneling rates whose fluctuations are greatly reduced, a phenomenon we call regularization of tunneling rates.

Responsivity optimization and stabilization in electro-optic field sensors.

Electro-optic (EO) modulation devices, which utilize an external electric field to modulate a beam of optical radiation, are strongly affected by parasitic effects, which change the polarization state of the optical beam. As a result, very small changes in the birefringence or optical path length within the EO material can result in very large fluctuations of the amplitude and phase of the optical modulation signal. A method of actively analyzing the modulated beam is described and demonstrated, which eliminates these fluctuations and keeps the modulation device stably operating at its peak responsivity.

Dielectrically induced sensitivity enhancements in electro-optic field sensors.

The sensitivity of an electro-optic (EO) field sensor depends inversely on the dielectric constant of the nonlinear crystal. In EO sensors based on lithium niobate the effective value of this dielectric constant is affected by dielectric relaxation effects and is identified with its smaller, high-frequency component. Because of this effect, the EO modulation is significantly enhanced, thus improving the field strength sensitivity.