Roland Himmelhuber

New Infrared Transmitting Material via Inverse Vulcanization of Elemental Sulfur to Prepare High Refractive Index Polymers

Polymers for IR imaging: The preparation of high refractive index polymers (n = 1.75 to 1.86) via the inverse vulcanization of elemental sulfur is reported. High quality imaging in the near (1.5 μm) and mid-IR (3-5 μm) regions using high refractive index polymeric lenses from these sulfur materials was demonstrated.

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.

A Silicon-Polymer Hybrid Modulator—Design, Simulation and Proof of Principle

Optimal dimensions are found for the silicon waveguide in an electro-optic (EO) polymer cladding-based silicon waveguide modulator. The confinement factor as well as the effective index of the mode are taken into account. The influence of the coplanar electrode spacing and electrode height on performance are examined and a figure of merit formula for choosing the optimal device geometry is shown. The design space for both 1550 nm and 1310 nm wavelengths is explored. With the optimal 275 nm waveguide width and 4 μm electrode spacing, a Vπ of a few volts can be achieved even with moderate r33 EO polymers. Experimental results on a fabricated modulator are shown and compared with the predicted performance.

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

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.

Silica/Electro-Optic Polymer Optical Modulator With Integrated Antenna for Microwave Receiving

A silica/electro-optic (EO) polymer phase modulator is proposed for microwave radiation receiver with the use of a bowtie antenna. Waveguide design optimization is presented for a waveguide with an EO polymer core and silica/sol-gel cladding. Electrode effects on the insertion loss and poling efficiency are also analyzed and conditions for low-loss and high poling efficiency established. The bowtie antenna is simulated and shows a broadband response with a maximum at 5 GHz and a 3 dB-bandwidth of approximately 12 GHz. A fiber splicing technique is presented that reduces coupling loss between SMF-28 and the waveguide. Experimental results for a fabricated device with microwave-response between 10-14 GHz are shown with carrier to first sideband intensity difference of up to -36 dB.

A survey on recent advances in optical communications

Recent advances in optical communications not only increase the capacities of communication system but also improve the system dynamicity and survivability. Various new technologies are invented to increase the bandwidth of individual wavelength channels and the number of wavelengths transmitted per fiber. Multiple access technologies have also been developed to support various emerging applications, including real-time, on-demand and high data-rate applications, in a flexible, cost effective and energy efficient manner. In this paper, we overview recent research in optical communications and focus on the topics of modulation, switching, add-drop multiplexer, coding schemes, detection schemes, orthogonal frequency-division multiplexing, system analysis, cross-layer design, control and management, free space optics, and optics in data center networks. The primary purpose of this paper is to refresh the knowledge and broaden the understanding of advances in optical communications, and to encourage further research in this area and the deployment of new technologies in production networks.

Titanium oxide sol-gel films with tunable refractive index

Glycidylmethacrylate and propylene oxide were used in the epoxide initiated formation of titanium oxide sols which were spun to form thin films. Glycidylmethacrylate can be used to tune the refractive index of the resulting composite and allowed us to photo-pattern the material. The refractive index of the films can be controlled between 1.76 and 2.05 at 589 nm. The thicknesses of the films ranged between 80 and 200 nm and the rms roughness below 2 nm. The films were characterized by atomic force microscopy (AFM), electric force microscopy (EFM), x-ray photoelectron spectroscopy (XPS) and ellipsometry, among other techniques.

Alignment-free fabrication of a hybrid electro-optic polymer/ion-exchange glass coplanar modulator

A hybrid electro-optic (EO) polymer phase modulator with a 6 μm coplanar electrode gap was realized on ion exchange glass substrates. The critical alignment steps which may be required for hybrid optoelectronic devices were eliminated with a simple alignment-free fabrication technique. The low loss adiabatic transition from glass to EO polymer waveguide was enabled by gray scale patterning of novel EO polymer, AJLY. Total insertion loss of 5 dB and electrode gap of 8 μm was obtained for an optimized device design. EO polymer poling at 135 °C and 75 V/μm was demonstrated for the first time on a phosphate glass substrate and was enabled by the sol-gel buffer layer.

Dielectric and electrical properties of sol-gel/DNA blends

We investigate the dielectric and electrical properties of sol-gel/DNA-CTMA blends, with particular interest in capacitor applications in energy storage. Methacryloyloxypropyltrimethoxysilane (MAPTMS) was the sol-gel precursor, and DNA-CTMA was blended in to the resulting sol-gel at 5 weight%. The blend was then tested for its dielectric properties and dielectric breakdown strength; at frequencies below 10kHz the blend was found to have a dielectric constant in the range of 7.5, while the breakdown strength was greater than 800 V/μm, an exceptional value. We discuss these results as well as other aspects of the dielectric and electrical properties of these blends.

HYBRID SOL-GEL ELECTRO-OPTIC POLYMER MODULATORS: BEATING THE DRIVE VOLTAGE/LOSS TRADEOFF

There has been great progress in the development of electro-optic (EO) polymers with exceptionally high r33 coefficients, with values ranging from 100–400 pm/V now being reported for single layer electro-optic polymer films. While this enables the fabrication of EO modulators with sub-volt operation, it is also necessary to make devices with acceptably low insertion loss (< 6 dB) in order to compete with existing technology. We have developed a solution to the voltage/insertion loss tradeoff in EO polymer modulators by adopting a hybrid geometry that provides for low optical coupling loss, electro-optic polymer limited propagation loss, highly efficient poling, and low cost fabrication. This combination of properties has allowed us to achieve r33 = 170 pm/V in an EO phase modulator. In addition to this proven approach to optimizing the figure of merit, there are several other approaches that can have high impact. The development of low loss EO polymer and cladding materials and waveguides can greatly reduce the insertion loss of EO polymer modulators, through chemical substitution techniques such as selective halogenation, as well as through improved processing to reduce roughness, stress and poling induced losses. Halogenation can be used to reduce the number of C–H bonds, which have well-known stretch and bend vibrational modes whose overtones extend into the optical communications bands at 1550 nm and 1310 nm. While roughness and stress effects are well-understood from work on passive waveguides, the poling process can produce inhomogeneities that lead to increased scattering loss; molecular design can be used to reduce poling induced loss. Another approach is to adopt non-waveguide device formats that are more tolerant of material losses, such as Fabry-Perot etalons. While etalons may not be viable for very high speed applications (i.e., GHz regime), they present entirely new application areas for electro-optic polymers.