Luis A. M. Barea

Reconfigurable silicon thermo-optical ring resonator switch based on Vernier effect control

A proof-of-concept for a new and entirely CMOS compatible thermo-optic reconfigurable switch based on a coupled ring resonator structure is experimentally demonstrated in this paper. Preliminary results show that a single optical device is capable of combining several functionalities, such as tunable filtering, non-blocking switching and reconfigurability, in a single device with compact footprint (~50 μm x 30 μm).

Embedded coupled microrings with high-finesse and close-spaced resonances for optical signal processing

Single microring resonators have been used in applications such as wavelength multicasting and microwave photonics, but the dependence of the free spectral range with ring radius imposes a trade-off between the required GHz optical channel spacing, footprint and power consumption. We demonstrate four-channel all-optical wavelength multicasting using only 1 mW of control power, with converted channel spacing of 40-60 GHz. Our device is based on a compact embedded microring design fabricated on a scalable SOI platform. The coexistence of close resonance spacing and high finesse (205) in a compact footprint is possible due to enhanced quality factors (30,000) resulting from the embedded configuration and the coupling-strength dependence of resonance spacing, instead of ring size. In addition, we discuss the possibility of achieving continuously mode splitting from a single-notch resonance up to 40 GHz.

Silicon technology compatible photonic molecules for compact optical signal processing

Photonic molecules (PMs) based on multiple inner coupled microring resonators allow to surpass the fundamental constraint between the total quality factor (QT), free spectral range (FSR), and resonator size. In this work, we use a PM that presents doublets and triplets resonance splitting, all with high QT. We demonstrate the use of the doublet splitting for 34.2 GHz signal extraction by filtering the sidebands of a modulated optical signal. We also demonstrate that very compact optical modulators operating 2.75 times beyond its resonator linewidth limit may be obtained using the PM triplet splitting, with separation of ∼55 GHz.

Comparison of Plasmonic Arrays of Holes Recorded by Interference Lithography and Focused Ion Beam

In this paper, we compare the geometric characteristics and the optical properties of plasmonic hole arrays recorded in gold (Au) films using two different techniques, namely, focused ion beam (FIB) and interference lithography (IL). The morphology of the samples was analyzed using a scanning electron microscope (SEM), and the plasmonic peaks were measured from the transmission spectrum of the samples. The diameters of the holes recorded by IL present approximately the same statistical deviation as those fabricated by FIB but in a much larger area. Although the transmittance measurements of both types of samples exhibit the characteristic plasmonic peaks, the intrinsic fabrication errors of each technique affect differently the optical spectra.

Spectral Engineering With CMOS Compatible SOI Photonic Molecules

Photonic systems based on microring resonators have a fundamental constraint given by the strict relationship among free spectral range, total quality factor QT , and resonator size, intrinsically making filter spacing, photonic lifetime, and footprint interdependent. Here, we break this paradigm employing CMOS-compatible silicon-on-insulator photonic molecules based on coupled multiple inner ring resonators. The resonance wavelengths and their respective linewidths are controlled by the hybridization of the quasi-orthogonal photonic states. We demonstrate photonic molecules with doublet and triplet resonances with spectral splitting only achievable with single-ring orders of magnitude larger in footprint. In addition, this splitting is potentially controllable based on the coupling (bonds) between resonators. Finally, the spatial distribution of the hybrid states allows up to sevenfold QT enhancement.

a-SiO x active photonic crystal resonator membrane fabricated by focused Ga + ion beam

We have fabricated thin erbium-doped amorphous silicon sub-oxide (a-SiOx) photonic crystal membrane using focused gallium ion beam (FIB). The photonic crystal is composed of a hexagonal lattice with a H1 defect supporting two quasi-doubly degenerate second order dipole states. 2-D simulation was used for the design of the structure and full 3-D FDTD (Finite-Difference Time-Domain) numerical simulations were performed for a complete analysis of the structure. The simulation predicted a quality factor for the structure of Q = 350 with a spontaneous emission enhancement of 7. Micro photoluminescence measurements showed an integrated emission intensity enhancement of ~2 times with a Q = 130. We show that the discrepancy between simulation and measurement is due to the conical shape of the photonic crystal holes and the optical losses induced by FIB milling.

Monolithic Erbium-Doped Al2O3 Waveguide Amplifier

We propose the development of an integrated optical amplifier, consisting of a 980 nm emission laser and an erbium-doped waveguide. Coupling simulations and current fabrication results are presented, which shows that the finished device should be able to achieve a gain of 1.55 dB/cm.

Photonic molecules for application in silicon-on-insulator optical sensors

Optical sensors based on integrated photonics have experienced impressive advancements in the past few decades and represent one of the main sensing solutions in many areas including environmental sensing and medical diagnostics. In this context, optical microcavities are extensively employed as refractive index (RI) sensors, providing sharp optical resonances that allow the detection of very small variations in the surrounding RI. With increased sensitivity, however, the device is subjected to environmental perturbations that can also change the RI, such as temperature variations, and therefore compromise their reliability. In this work, we present the concept and experimental realization of a photonic sensor based on coupled microcavities or Photonic Molecules (PM) in which only one cavity is exposed to the sensing solution, allowing a differential measurement of the RI change. The device consists of an exposed 5-μm radius microdisk resonator coupled to an external clad microring resonator fabricated on silicon-on-insulator (SOI) platform. This design allows good sensitivity (26 nm/RIU) for transverse electrical mode (TE-mode) in a compact footprint (40 × 40 μm2), representing a good solution for real-life applications in which measurement conditions are not easily controllable.

Low-power four-channel wavelength multicasting in embedded microring resonators

We demonstrate four-channel all-optical wavelength multicasting using only 1 mW of pump power and channel spacing of 40-60 GHz. Our device is based on a compact embedded microring design fabricated on a scalable SOI platform.

High Frequency Double-disk Optomechanical Oscillators

We propose a double-disk optomechanical resonator with mechanical frequency close to 1 GHz. The design is based on the optimization of the optomechanical interaction of a second-order mechanical mode.