A. K.-Y. Jen

Optical modulation and detection in slotted Silicon waveguides

We demonstrate a novel mechanism for low power optical detection and modulation in a slotted waveguide geometry filled with nonlinear electro-optic polymers. The nanoscale confinement of the optical mode, combined with its close proximity to electrical contacts, enables the direct conversion of optical energy to electrical energy, without external bias, via optical rectification, and also enhances electro-optic modulation. We demonstrate this process for power levels in the sub-milliwatt regime, as compared to the kilowatt regime in which optical nonlinear effects are typically observed at short length scales. Our results suggest that a new class of detectors based on nonlinear optics may be practical.

Hybrid cross-linkable polymer/sol-gel waveguide modulators with 0.65V half wave voltage at 1550nm

The authors report on a hybrid cross-linked electro-optic (EO) polymer/sol-gel Mach-Zehnder waveguide modulator with a half wave voltage (Vπ) of 0.65V at 1550nm. The low Vπ was achieved by a design that (1) combines both physical vertical tapers in the sol-gel core and photobleached index tapers in the EO polymer and (2) reduces the thickness of the device to 8μm. These combined physical and index tapers result in improved optical mode confinement in the EO polymer with low adiabatic optical transition loss. The reduced thickness results in a larger field across the EO polymer for the same voltage, enabling a lower Vπ.

Demonstration of a low V π L modulator with GHz bandwidth based on electro-optic polymer-clad silicon slot waveguides

We demonstrate a near-infrared electro-optic modulator with a bandwidth of 3 GHz and a V(pi)L figure of merit of 0.8 V-cm using a push-pull configuration. This is the highest operating speed achieved in a silicon-polymer hybrid system to date by several orders of magnitude. The modulator was fabricated from a silicon strip-loaded slot waveguide and clad in a nonlinear polymer. In this geometry, the electrodes form parts of the waveguide, and the modulator driving voltage drops across a 200 nm slot.

High-performance polymer light-emitting diodes fabricated with a polymer hole injection layer

Enhanced luminance (L) and luminous efficiency (LE) of polymer light-emitting diodes (PLEDs) is demonstrated using poly(bis(tetraphenyldiamino)biphenyl-perfluorocyclobutane), poly(BTPD-Si-PFCB), as the hole injection layer. The monomer is cast directly onto the indium-tin-oxide anode and thermally polymerized in situ. Hole injection from poly(BTPD-Si-PFCB) into the “super yellow” derivative of poly(phenylene vinylene) and into several blue-emitting polymers is comparable to or better than that from poly(ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSSA). With poly(BTPD-Si-PFCB) as the hole injecting layer into “super yellow,” the performance is identical to that obtained with PEDOT:PSSA (LE≈8 cd/A with little fall-off, even at L>104 cd/m2).

Pockel’s coefficient enhancement of poled electro-optic polymers with a hybrid organic-inorganic sol-gel cladding layer

Ultraefficient poling of electro-optic polymers is reported using an organically modified sol-gel cladding layer. This poling technique has resulted in a Pockel’s coefficient enhancement of up to a factor of 2.5, going from 26pm∕V when poled without a sol-gel cladding to 65pm∕V when optimally poled with a sol-gel cladding. The poling process directly applies to a previously reported hybrid electro-optic polymer/sol-gel waveguide modulator and may have applications in other poled polymer based devices.

Low half-wave voltage and high electro-optic effect in hybrid polymer/sol-gel waveguide modulators

The authors report on hybrid electro-optic (EO) polymer–sol-gel modulators with low half-wave voltage (Vπ) and low insertion loss. Larger EO coefficient r33 results from the high poling field achieved when EO polymer is sandwiched between sol-gel cladding layers. The reduced interelectrode distance (d) resulting from the elimination of the sol-gel core layer in the active region further reduces Vπ. Straight channel phase modulators operate with Vπ=4.2V at 1550nm using a reduced d of 11.5μm, which corresponds to an r33 of 78pm∕V, among the highest r33 reported. The authors also examine a Mach-Zehnder modulator with Vπ=3.9V using a conventional d of 15μm.

Hybrid electro-optic polymer and selectively buried sol-gel waveguides

An approach to utilizing electro-optically (EO) active polymers in hybrid waveguide structures is described and demonstrated. Buried sol-gel waveguides provide a robust basis for planar integrated circuitry, suitable for coupling with optical fibers. By selectively exposing the core of a buried channel guide, overcoating with an EO polymer, and using appropriately tapered transition zones, a guided mode can be made to undergo adiabatic transitions from sol-gel waveguide up into the EO polymer and back. Such a single-mode device was constructed. These transitions were proven via modulation of the emerging wave’s polarization ellipse by application of voltage to the EO polymer.

Mesoscale Dynamics and Cooperativity of Networking Dendronized Nonlinear Optical Molecular Glasses

First, molecular scale insight into the mobility of a novel class of organic materials for photonic applications with electro-optical activities larger than 300 pm/V is presented. A representative second order nonlinear optical (NLO) material of this class of self-assembling molecular glasses involving quadrupolar phenyl-perfluorophenyl (Ph-PhF) interactions is analyzed based on its molecular relaxation phenomena and phase behavior. Thereby, a new and straightforward nanoscale methodology, involving shear modulation force microscopy and intrinsic friction analysis is introduced. It provides both the submolecular enthalpic and entropic dynamics in nanoconstrained systems (e.g., ultrathin films), and thus, insight into local motion of single molecules due to dissociation of Ph-PhF pairs as well as the cooperative dynamics of the assembled network. This nanoscale model-independent thermomechanical methodology is shown to be very effective in fundamentally evaluating appropriate poling conditions of organic NLO materials. It promises to be a straightforward analysis tool to guide organic material synthesis from a molecular mobility perspective, particularly for applications that impose nanoscale constraints on the system.

High Δn strip-loaded electro-optic polymer waveguide modulator with low insertion loss

We demonstrate a novel electro-optic polymer modulator design which shows a record low optical insertion loss of 5.7 dB at 1550 nm. The modulator consists of a high numerical aperture passive waveguide which is converted to a strip-loaded electro-optic polymer waveguide through refractive index tapers. The device is fabricated using all wet-etch techniques which results in low excess loss from roughness created during fabrication and, employs new low loss passive sol-gel materials. The fabricated device also shows a low half-wave voltage of 2.8 V.

Hybrid electro-optic polymer/sol–gel waveguide modulator fabricated by all-wet etching process

A simple all-wet-etch process fabricates a hybrid electro-optic-polymer (EOP)/sol–gel waveguide modulator, confining the EOP laterally in the sol–gel overcladding. The structure enables an adiabatic transition between the passive sol–gel waveguides and the active EOP overlayers without lateral radiation. Intensity is confined well in a 0.9-μm-thick EOP overlayer, resulting in a low half-wave voltage (Vπ) due to the larger overlap integral. This lateral confinement technique allowed the reduction of Vπ (at 1550 nm) by a factor of 4.