Oscar D. Herrera

Structure-based optical filtering by the silica microshell of the centric marine diatom Coscinodiscus wailesii

Diatoms are a renewable (biologically reproducible) source of three-dimensional (3-D) nanostructured silica that could be attractive for a variety of photonic devices, owing to the wide range of quasi-periodic patterns of nano-to-microscale pores available on the silica microshells (frustules) of various diatom species. We have investigated the optical behavior of the silica frustule of a centric marine diatom, Coscinodiscus wailesii, using a coherent broadband (400-1700 nm) supercontinuum laser focused to a fine (20 µm diameter) spot. The C. wailesii frustule valve, which possessed a quasi-periodic hexagonal pore array, exhibited position-dependent optical diffraction. Changes in such diffraction behavior across the frustule were consistent with observed variations in the quasi-periodic pore pattern.

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.

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.

Slow light based on stimulated Raman scattering in an integrated liquid-core optical fiber filled with CS2

We demonstrate a fiber-based slow light system using a carbon disulfide (CS2)) filled integrated liquid-core optical fiber (i-LCOF). Using 1 meter of i-LCOF we were able to delay 18ps pulses up to 34ps; a delay of 188% of the pulse width. This experimental setup serves as a foundation for slow-light experiments in other nonlinear liquids. Numerical simulations of pulse-propagation equations confirmed the observed delay and a simplified method is presented that can be applied to calculate induced delay for non-cw Stokes pulses. The system is all-fiber and compact with delays greater than a pulse width, indicating potential application as an ultrafast controllable delay line for time division multiplexing in multiGb/s telecommunication systems.

Silicon/electro-optic polymer hybrid directional coupler switch

A silicon waveguide in an electro-optic (EO) polymer cladding-based directional coupler switch was designed and fabricated. Optimal dimensions for efficient coupling and minimal crosstalk are found analytically (coupled mode theory) and numerically for 1550nm wavelength. Both coplanar electrode spacing and height are taken into account for most effective poling conditions and performance. The design consists of two 255nm wide waveguides separated by 500nm and is optimized for TE propagation. With an electrode separation of 4μm and coupling length of 1.7cm, a switching voltage (Vs) < 10V at an r33 of 250pm/V is expected.

Electro-optic polymer channel waveguide fabrication using multiphoton direct laser writing

An all-reflective multiphoton microscope has been used for direct laser lithography and photo-bleaching of SEO250 EO polymer using a 1550nm femtosecond laser to fabricate 4μm channel waveguides. Waveguide loss and cladding index change have also been investigated.

Characterization of coplanar poled electro optic polymer films for Si-photonic devices with multiphoton microscopy

The authors demonstrated the feasibility of second-harmonic microscopic imaging for the the characterization of poled polymer film for application in silicon electro-optic polymer hybrid devices. The results are so far qualitative and can be used to optimize the poling conditions as long as the sample geometry is preserved.

A silicon-polymer hybrid modulator — 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. With the optimal 275 nm waveguide width and 4 μm electrode spacing, Vπ of a few volts can be achieved even with low r33 EO polymers.

Surface-Enhanced Two-Photon Excitation Fluorescence of Various Fluorophores Evaluated Using a Multiphoton Microscope

We present a rapid, low-power testbed for the detection and imaging of fluorescent probes utilizing two-photon excitation fluorescence (2PEF). The 2PEF signal from fluorophores commonly used in biological imaging have been enhanced using plasmonic substrates that have been designed to have a high plasmonic resonance over a narrow band that matches the source. The samples were illuminated and imaged using a low-power, in-house multiphoton microscope. A green fluorescent protein (bfloGFPa1), chlorophyll, or rhodamine 6G were deposited onto the plasmonic substrates and their 2PEF signals were measured relative to planar samples. The fluorescence intensities from the green fluorescent protein, chlorophyll, and rhodamine were enhanced by factors of 50, 8, and 4, respectively, with the structured substrates (relative to the planar substrates).

Corrections to “A Silicon-Polymer Hybrid Modulator—Design, Simulation, and Proof of Principle” [Dec 13 4067-4072]

In the article, “A Silicon-polymer hybrid modulator—Design, simulation and proof of principle”(Himmelhuber, R. ibid, vol. 31, no. 24, pp. 4067–4072, Dec. 2013], an error was found in the code used for calculating the line capacitance of a the CPS electrode design.