Organic Electro-Optic and
All-Optical Materials and Devices
Thrust 1 Research Projects
EO and Spatial Light Modulators; Hybrid Integration with Silicon
To develop improved materials to modulate electrical and optical signals, CMDITR researchers work to:
- Maximize bandwidth so that the material can carry as much information as possible;
- Minimize the voltage required for device operation in order to minimize power consumption and heat generation; and
- Minimize insertion loss and, therefore, signal degradation.
In addition, CMDITR will strive to ensure that materials meet the practical requirements of facile processibility and resistance to physical, optical, and thermal fatigue. Stability has been dramatically enhanced by the development and implementation of new lattice-hardening chemistries. Theory, ranging from first-principles quantum-chemical approaches applied to molecular systems to statistical mechanics applied to understand the behavior of composite materials, plays an important role in guiding a rational design process for synthesizing the best candidate chromophores and for nanoengineering of material lattices. In parallel with materials development, CMDITR researchers utilize high-r33 EO materials to build novel high-speed modulators and organic/Si hybrid integrated devices.
This project also seeks to efficiently incorporate nonlinear organic materials into silicon photonic devices through the use of strong nonlinear optical properties of organic materials for new frequency generation (sum and difference frequency generation, second and third harmonic generation) and up-converted fluorescence due to nonlinear absorption. Using this approach, CMDITR expects to achieve mode volumes that are 100 times smaller than what was believed to be possible in these systems, giving devices the potential to be 100 times more efficient.
- Theory-Guided Design and Synthesis of Highly Efficient NLO Chromophores and EO Materials
Optical Response of Explicitly and Continuum Solvated Chromophores
- Simulation for Enhancing the Efficiency and Polar Order of EO Materials
- Tuning the Kinetics and Energetics of Diels-Alder Cycloaddition Reactions to Improve Poling Efficiency and Thermal Stability of High Temperature Crosslinked Electro-Optic Polymers
- Supramolecular Engineering of Organic EO Materials with Large Pockels Coefficients for Ultra-Low Temperature (40K) Modulators
- High Non-centrosymmetric Order Parameter and Large EO Coefficient of Guest-Host Polymers
- New "Molecular Threading" Effect to Enhance Interchain Interactions of E-O Polymers for THz Applications
- Single-Molecule Studies of Molecular Photostability
- Low Insertion Loss Hybrid EO Polymer/Ion-Exchange Modulators
- Mach-Zehnder interferometer measurements of EO and piezoelectric coefficients of EO polymers
- Fabrication of Si Slot Waveguide for E-O Modulators
- Progress Toward Ultra-low Vπ Modulators
- Lossless mode size converters for efficient fiber coupling to polymer clad silicon slot waveguides
Materials and Devices for Terahertz Generation and Detection
The bandwidth available from most commercial lasers today is around 3.5 THz because of limitations in the materials used for the emitter and detector (typically inorganic EO crystals such as ZnTe). By combining very short laser pulses with EO polymers, the entire 100-THz bandwidth, with no spectral gaps, can potentially be made available. This is of great interest from a security standpoint since accurate discrimination of chemical/biological agents and explosives requires spectroscopic capabilities in the 5-30 THz spectral range. Building on our successful demonstration of a wide bandwidth (> 12 THz) gapfree THz system based on EO polymers, CMDITR researchers are striving to utilize this advance to create a THz spectrometer that has an even wider bandwidth response (0-30 THz) and a brighter THz source. Successful implementation of such a system will require identification of materials with low absorption in that band, low group velocity dispersion (GVD), and very high EO coefficient (r33 preferably > 300 pm/V).
- Terahertz Signal Generation and Detection
- Optical-pump THz-probe (OPTP) spectroscopy of organic photovoltaic materials (Projects 4.1)
Materials with Large All-Optical Nonlinearities; Devices and Subsystems
In order to develop polymers with sufficiently large third-order nonlinear susceptibility (χ(3)) for optical switching applications, CMDITR will refine current models that relate χ(3) to chemical structure. Specifically, CMDITR is developing materials with extensive delocalization beyond that which can be found in simple polymers, and with heightened optical nonlinearities arising from charge-transfer transitions. These approaches may yield materials with unprecedented performance at telecommunication wavelengths. In addition, CMDITR will investigate applications that take advantage of efficient twophoton absorption and third-harmonic generation. While ordering of chromophores is a well-understood key element in second-order nonlinear optical materials, the role of order in third-order nonlinear optical materials is poorly understood. Accordingly CMDITR will examine, both theoretically and experimentally, how chromophore ordering and aggregation can be used to significantly enhance χ(3).