High Performance Electric-Field Sensor Based on Enhanced Electro-Optic Polymer Refilled Slot Photonic Crystal Waveguides

ABSTRACT: This Phase II STTR research proposal aims to demonstrate an antenna coupled phase modulator based on an Electro-optic (EO) polymer refilled slot photonic crystal waveguide (PCW) for operation in the Q band. The goal is to detect field strengths of 100uW/m^2 in an Intensity Modulation Direct Detection (IMDD) scheme using subwavelength antennas. The EO polymer is the SEO125 provided by Dr. Alex Jen from University of Washington. The device benefits from high electro-optic coefficient (r33>150pm/V) from the EO polymer, slow light effect (>20) and concentration of high energy photons in a 320nm wide slot from the PCW and over 10000 electric field enhancement inside the slot provided by the antenna. The PCW structure makes possible a short antenna-waveguide interaction length of only 300um allowing for a very large RF-operation bandwidth (over 7GHz 1dB-bandwidth at 10GHz). The Phase I efforts focused on demonstration of low loss PCWs (grating coupled), low-dispersion slow-light PCWs, integration of high performance EO polymer (SEO125) with the PCW, RF (10GHz) and optical simulations of the antenna coupled modulator, demonstration of 10GHz operation. Building on the results from Phase I, we will fabricate a pigtailed antenna coupled modulator device on a glass substrate for operation over 30GHz. BENEFIT: The applications of the proposed device are in two main areas: Phased Array Antennas (PAAs) and Electromagnetic (EM) field sensors. Advanced onboard optical networks are expected to be deployed on future aircrafts and to replace the conventional bulky and heavy electrical networks. Onboard RF-Photonic systems can efficiently accomplish high throughput data communication as well as beam scanning through PAAs. On the other hand, EM field measurements are ubiquitous in various scientific and technical areas, including process control, EM-field monitoring in medical apparatuses, ballistic control, electromagnetic compatibility measurements, microwave integrated circuit testing, and detection of directional energy weapon attack. Conventional EM wave measurement systems use active metallic probes, which disturb the EM waves to be measured and render the sensor very sensitive to electromagnetic noises. Photonic EM-field sensors exhibit significant advantages over the electronic ones due to their smaller size, lighter weight, higher sensitivity, and broader bandwidth. Compared to the conventional photonic EM field sensors, the proposed device provides an unprecedented sensitivity over a large frequency range through 4 orders of magnitude field-enhancement from a subwavelength antenna and the short length of the modulator made possible by a photonic crystal waveguide structure and a high performance electro-optic polymer.