We design and fabricate a 320 nm slot for an electro-optic (E-O) polymer infiltrated silicon photonic crystal waveguide. Because of the large slot width, the poling efficiency of the infiltrated E-O polymer (AJCKL1/amorphous polycarbonate) is significantly improved. When coupled with the slow light effect from the silicon photonic crystal waveguide, an effective in-device r33 of 735 pm/V, which to our knowledge is a record high, is demonstrated, which is ten times higher than the E-O coefficient achieved in thin film material. Because of this ultrahigh E-O efficiency, the VπL of the device is only 0.44 V mm, which is to our knowledge the best result of all E-O polymer modulators.

Effective in-device r_33 of 735 pm/V on electro-optic polymer infiltrated silicon photonic crystal slot waveguides

We design and demonstrate a compact and low-power, band-engineered, electro-optic (EO) polymer refilled silicon slot photonic crystal waveguide (PCW) modulator. The EO polymer is engineered for large EO activity and near-infrared transparency. A PCW step coupler is used for optimum coupling to the slow-light mode of the band-engineered PCW. The half-wave switching voltage is measured to be Vπ=0.97±0.02  V over an optical spectrum range of 8 nm, corresponding to the effective in-device r33 of 1190  pm/V and Vπ×L=0.291±0.006  V×mm in a push–pull configuration. Excluding the slow-light effect, we estimate that the EO polymer is poled with an efficiency of 89  pm/V in the slot.

http://chen-server.mer.utexas.edu/2013/ol-38-22-4931.pdf

Wide optical spectrum range, subvolt, compact modulator based on an electro-optic polymer refilled silicon slot photonic crystal waveguide.

We design and demonstrate a compact and low-power band-engineered electro-optic (EO) polymer refilled silicon slot photonic crystal waveguide (PCW) modulator. The EO polymer is engineered for large EO activity and near-infrared transparency. A PCW step coupler is used for optimum coupling to the slow-light mode of the band-engineered PCW. The half-wave switching-voltage is measured to be V{\pi}=0.97+-0.02V over optical spectrum range of 8nm, corresponding to the effective in-device r33 of 1190pm/V and V{\pi} L of 0.291+-0.006V mm in a push-pull configuration. Excluding the slow-light effect, we estimate the EO polymer is poled with an efficiency of 89pm/V in the slot.

Wide optical spectrum range, sub-volt, compact modulator based on electro-optic polymer refilled silicon slot photonic crystal waveguide

Integrated (multi-scale) quantum and statistical mechanical theoretical methods have guided the nano-engineering of controlled intermolecular electrostatic interactions for the dramatic improvement of acentric order and thus electro-optic activity of melt-processable organic polymer and dendrimer electro-optic materials. New measurement techniques have permitted quantitative determination of the molecular order parameters, lattice dimensionality, and nanoscale viscoelasticity properties of these new soft matter materials and have facilitated comparison of theoretically-predicted structures and thermodynamic properties with experimentally-defined structures and properties. New processing protocols have permitted further enhancement of material properties and have facilitated the fabrication of complex device structures. The integration of organic electro-optic materials into silicon photonic, plasmonic, and metamaterial device architectures has led to impressive new performance metrics for a variety of technological applications.

Theory-Guided Design of Organic Electro-Optic Materials and Devices

Lowering the operating voltage of electro-optic modulators is desirable for a variety of applications, most notably in analog photonics and digital data communication. In particular for digital systems such as CPUs, it is desirable to develop modulators that are both temperature-insensitive and compatible with typically sub-2 V CMOS electronics; however, drive voltages in silicon-based Mach-Zehnder interferometers (MZIs) currently exceed 1.8 V. Here, we show an MZI modulator based on an electro-optic polymer-clad silicon slot waveguide, with a halfwave voltage of only 0.69 V (corresponding to a 0.62 V(·)cm modulation figure of merit), and a bandwidth of 500 MHz. We also show that there are paths to significantly improve both the bandwidth and drive voltage.

Sub-Volt Silicon-Organic Electro-optic Modulator With 500 MHz Bandwidth

A Mach–Zehnder interferometer (MZI) is utilized to decouple the electro-optic and piezoelectric tensor effects occurring in a poled polymer film. This method has significant advantages over the commonly used Teng-Man reflection ellipsometry technique by allowing for the independent determination of the Pockel’s coefficients r13 and r33 and the piezoelectric coefficient d33. The r33 value of a guest host polymer that consists of AJLZ53 amorphous polycarbonate was found to be 122.69 pm/V and 123.03 pm/V using the MZI and reflection ellipsometry method, respectively. The r33 data fits well to the dispersion of the second order susceptibility tensor based on the two-level model approximation.

Mach–Zehnder interferometry method for decoupling electro-optic and piezoelectric effects in poled polymer films

A Mach-Zehnder interferometer (MZI) is used to decouple the 
electro-optic (EO) and piezoelectric tensor
components for a poled polymer film. In the past those using the MZI method failed to take into account the
piezoelectric contribution in the polymer which can lead to erroneous EO coefficient data. The typical poled sample of
polymer sandwiched between ITO glass and gold that was developed for the popular Teng-Man reflection ellipsometry
method is used, providing for easy comparison with that method. The sample serves as a mirror in one arm of the
interferometer with the gold side facing the beam for measuring the piezoelectric modulation and the glass side facing
the beam to measure the coupled piezoelectric and EO modulation. Optical biasing in the reference arm allows for the
baseline and modulated contrast of the system to be measured from which the tensor components are calculated. This
method has the advantage over the reflection ellipsometry method of allowing for the independent determination of the
Pockel's coefficients r13 and r33 and the piezoelectric coefficient d33. The r33 value of a guest host polymer that consists
of AJLZ53/amorphous polycarbonate (APC) was found to be 122.7 pm/V and 123.0 pm/V for the MZI and reflection
ellipsometry method respectively. The r33 data fits well to the dispersion of the second order susceptibility tensor 
χ 333 (2)
based on the two-level model approximation. Measurements were done from 100 Hz to 100 kHz with the results
showing that at higher frequencies the mechanical effects in the sample are negligible and modulation is almost entirely
due to the EO effect, as expected.

Ayodeji Opadeyi

Papers

Mach–Zehnder interferometry method for decoupling electro-optic and piezoelectric effects in poled polymer films

Mach-Zehnder interferometry method for decoupling electro-optic and piezoelectric tensor components in poled polymer films