Abstract: Improved optical interferometric modulators have a small waveguide spacing so that the waveguide pair are close to the central electrode, to enhance electro-optic interaction. Asymmetric waveguides with differential indices are used to effectively de-couple the waveguide pair. Multiple sections of asymmetric waveguide pairs with alternating differential indices are used to achieve chirp-free operation. Another version of the device utilizes transmission-line electrode that weave closer to one of the waveguide pair alternately between sections. Another version of the device utilizes waveguide structure that one of the waveguide is closer to the central electrode in alternate section. To improve efficiency further, a DC bias is provided on the outer electrodes configured as an RF-ground but DC-float electrodes. Another improvement is to have a slot is cut underneath the waveguide region to effectively reduce to thickness of the substrate. These improvements lead to higher modulator efficiency.

Abstract: A new High-Z optical modulator has a waveguide and electrodes on a substrate, a buffer layer with a low dielectric constant between the waveguide and the substrate, and a substance between the waveguide and the substrate with a dielectric constant lower than a dielectric constant of the substrate to the side and below the plane of the waveguide, thereby improving electro-optic field overlap, increasing RF speed and increasing transmission line impedance. The material with a dielectric constant lower than the substrate extends between the waveguide and the electrodes to a depth below the waveguide equal to or greater than the lateral distance between the waveguide and electrodes. This material may be air and may be introduced by cutting away portions of the substrate around the waveguide with a precision dicing saw. The electrodes may be placed even with the waveguide or below the waveguide on the cut-away portion of the substrate.

Abstract: A cw-laser source transmits low-noise, narrow-linewidth optical power via an optical fiber to a bias-free electro-optic phase modulator at a remote site, where an antenna or an RF sensor is located. The RF electrical signal modulates the phase modulator at the remote site, converting an electrical signal into an optical signal. The phase-modulated optical signal is fed back via the optical fiber to an optical filter whose filter transfer characteristics can be tuned and reconfigured to cancel the intermodulation distortion terms, particularly the dominant 3rd order intermodulation, as well as the 2nd order. The filtered optical signal is converted to the RF signal at the photodetector. The optical filter is used to effectively “linearize” the signal at the receiver end, rather than at the modulator end.

Abstract: Optical switches based on the balanced bridge interferometer design require precisely made (or half a coupling length) directional couplers to achieve minimum crosstalk for the two switch outputs. Precision 3 dB-directional couplers require the waveguide dimensions and fabrication parameters of the evanescent region to be tightly controlled making a low crosstalk switch difficult to manufacture and expensive. A new type of balanced bridge interferometer type switch is disclosed where the input and output directional couplers are asymmetrically biased to induce a certain difference in the propagation constants between the two waveguide in the directional couplers. By using the asymmetrically biased directional couplers with a certain tuning a bias voltage for the directional couplers. Low crosstalk switches can be achieved for a very wide range of directional coupler strengths, relaxing the precise half-coupling length directional couplers required in conventional design.