Peter Girouard

Characterization of Electrodynamic Screen Performance for Dust Removal from Solar Panels and Solar Hydrogen Generators

The direct solar energy conversion in gigawatt scales by photovoltaic, photothermal, and photoelectrochemical processes is of national and global importance in meeting energy needs. Dust depositions on solar panels and solar concentrators cause efficiency loss from 10% to 30% depending upon the surface mass concentration of dust requiring manual cleaning with water. Such a cleaning process is expensive for large-scale installations where water is scarce. Transparent electrodynamic screens, consisting of rows of transparent parallel electrodes embedded within a transparent dielectric film, can be used for dust removal for their application as self-cleaning solar collectors. When the electrodes are activated by phased voltage, the dust particles on the surface of the film become electrostatically charged and are removed by the traveling wave generated by applied electric field. Over 90% of deposited dust is removed within 2 min, using a very small fraction of the energy produced by the panels. No water or mechanical movement is involved. An analysis of the electrodynamic removal mechanisms based on electrostatic and dielectrophoretic forces opposed by the adhesion forces due to van der Waals and image forces is presented.

Integrated BaTiO3 modulator with 8 dB extinction at 50 GHz and 25 km reach

We demonstrate the high frequency and long-reach performance of a compact modulator using thin film BaTiO₃. An extinction of 12 dB is measured at 25 GHz for 2.2 V_pp operation through a 25 km fiber with 8 dB extinction at 50 GHz for 9.1 V_pp.

Small footprint barium titanate photonic crystal modulators for photonic integrated circuits

We report on the design, fabrication, and characterization of photonic crystal phase modulators on epitaxial barium titanate thin films. Modeling indicates that >50 GHz bandwidth and 0.25 V·cm voltage-length product are achievable in sub-millimeter long devices.

Ultrahigh Bandwidth, Low V π Photonic Crystal BaTiO 3 Modulators

BaTiO3 modulators with as low as 3.9 V Vπ and as high as 28 GHz bandwidth are reported. We demonstrate photonic crystal waveguides with a group index of 4 and predict > 50 GHz bandwidth and < 5 V operation in optimized photonic crystal modulators.

BaTiO3 Modulator Devices for Silicon Photonics

The microwave characteristics of thin-film BaTiO3 traveling-wave electro-optic modulators were measured between 10 MHz and 50 GHz. S-parameter measurements show a smooth response to 50 GHz and up to 50 GHz electrical bandwidth.

SiNOI and AlGaAs-on-SOI nonlinear circuits for continuum generation in Si photonics

In this communication, we report on the design, fabrication, and testing of Silicon Nitride on Insulator (SiNOI) and Aluminum-Gallium-Arsenide (AlGaAs) on silicon-on-insulator (SOI) nonlinear photonic circuits for continuum generation in Silicon (Si) photonics. As recently demonstrated, the generation of frequency continua and supercontinua can be used to overcome the intrinsic limitations of nowadays silicon photonics notably concerning the heterogeneous integration of III-V on SOI lasers for datacom and telecom applications. By using the Kerr nonlinearity of monolithic silicon nitride and heterointegrated GaAs-based alloys on SOI, the generation of tens or even hundreds of new optical frequencies can be obtained in dispersion tailored waveguides, thus providing an all-optical alternative to the heterointegration of hundreds of standalone III-V on Si lasers. In our work, we present paths to energy-efficient continua generation on silicon photonics circuits. Notably, we demonstrate spectral broadening covering the full C-band via Kerrbased self-phase modulation in SiNOI nanowires featuring full process compatibility with Si photonic devices. Moreover, AlGaAs waveguides are heterointegrated on SOI in order to dramatically reduce (x1/10) thresholds in optical parametric oscillation and in the power required for supercontinuum generation under pulsed pumping. The manufacturing techniques allowing the monolithic co-integration of nonlinear functionalities on existing CMOS-compatible Si photonics for both active and passive components will be shown. Experimental evidence based on self-phase modulation show SiNOI and AlGaAs nanowires capable of generating wide-spanning frequency continua in the C-Band. This will pave the way for low-threshold power-efficient Kerr-based comb- and continuum- sources featuring compatibility with Si photonic integrated circuits (Si-PICs).

50 GHz electro-optic modulators with BaTiO3 epitaxial thin film platform for short distance optical communications

Future datacom and telecom applications as well as optical interconnects require high bandwidth, low-power, small area optical modulator devices [1], [2], [3], [4], [5]. No device technology to date has been shown with the concomitant properties of high electro-optic (EO) bandwidth, wide optical range, low power consumption, and compact size. We have taken an alternative approach of developing thin film BaTiO3 as an optoelectronic material platform for high frequency, low operation voltage, and compact modulators. The BaTiO3 thin film platform has competitive advantages over other legacy platforms for optical modulator applications. In brief, ferroelectric oxide thin film BaTiO3 modulators have advantages of: (1) large EO coefficient, more than ten times higher compared to those of LiNbO3 devices currently dominating optical modulator markets; (2) low driving voltage of <1.5 V, thus low power consumption; (3) bandwidth >50 GHz demonstrated with potential reaching 100 + GHz regime; (4) potential for medium scale integration; and (5) integration with Si electronics leading to ultrahigh compact electrooptical components at low cost [6]. Using BaTiO3 thin films with 1 mm long interaction length, we have demonstrated optical modulators with voltage-length products nearly an order of magnitude smaller than that of silicon [7]. We have also shown the potential for high frequency operation by demonstrating modulation out to 50 GHz [7], [8], [9].

Enhancement of the pockels effect in photonic crystal modulators through slow light

We report a photonic crystal (PhC) optical modulator operating in the optical C band (1530-1565 nm) using barium titanate epitaxial thin films as the electro-optic (EO) medium. The PhC has hexagonal lattice symmetry and an extinction ratio of 9 dB. Due to the slow light enhancement of the EO coefficient near the PhC band edge, the driving electrode can be as short as a one millimeter. We report for the first time, to the best of our knowledge, at microwave frequencies from 10 to 45 GHz the effective EO coefficient and its enhancement through slow light effects. A monotonic increase of the effective EO coefficient from 60 to 110 pm/V across the stopband edge is obtained, resulting in an enhancement as high as 1.8.