Multifunction optical filter with a Michelson-Gires-Tournois interferometer for wavelength-division-multiplexed network system applications

Trilayered Gires-Tournois Resonator with Ultrasensitive Slow-Light Condition for Colorimetric Detection of Bioparticles

Over the past few decades, advances in various nanophotonic structures to enhance light-matter interactions have opened numerous opportunities for biosensing applications. Beyond the successful development of label-free nanophotonic biosensors that utilize plasmon resonances in metals and Mie resonances in dielectrics, simpler structures are required to achieve improved sensor performance and multifunctionality, while enabling cost-effective fabrication. Here, we present a simple and effectual approach to colorimetric biosensing utilizing a trilayered Gires-Tournois (GT) resonator, which provides a sensitive slow-light effect in response to low refractive index (RI) substances and thus enables to distinguish low RI bioparticles from the background with spatially distinct color differences. For low RI sensitivity, by impedance matching based on the transmission line model, trilayer configuration enables the derivation of optimal designs to achieve the unity absorption condition in a low RI medium, which is difficult to obtain with the conventional GT configuration. Compared to conventional bilayered GT resonators, the trilayered GT resonator shows significant sensing performance with linear sensitivity in various situations with low RI substances. For extended applications, several proposed designs of trilayered GT resonators are presented in various material combinations by impedance matching using equivalent transmission line models. Further, comparing the color change of different substrates with low RI NPs using finite-difference time-domain (FDTD) simulations, the proposed GT structure shows surpassing colorimetric detection.

Integrated Gires-Tournois interferometers based on evanescently coupled ridge resonators

We propose integrated Gires-Tournois interferometers (GTIs) for guided modes of dielectric slab waveguides. The proposed GTIs consist of one or several dielectric ridge resonators separated by subwavelength-width grooves patterned into an abruptly terminated slab waveguide and operate at oblique incidence of the fundamental transverse-electric-polarized mode. The grooves act as partially reflective mirrors, whereas the end facet of the last ridge works in the total internal reflection regime and reflects all the incident radiation. We show that the single-ridge structure provides a nonlinear staircase-like phase response characteristic for GTIs. By using several properly arranged ridges, one can engineer group delay or group delay dispersion in a required spectral range. As an example, we design a three-ridge GTI providing an almost constant group delay dispersion in a 50-nm-wide wavelength range. The proposed planar GTIs may find application in integrated optical circuits for introducing or compensating for chromatic dispersion.

Design of a birefringent Michelson interferometer-based interleaver with ultra-low dispersion and low cost

We design and demonstrate a birefringent Michelson interferometer based interleaver with ultra-low dispersion and low cost. The interleaver consists of polarizing beam splitters (PBS's) and quarter-wave plates and half-wave plates. The PBS's based Michelson interferometers provide the optical path difference for interference between the two orthogonal polarization components and the half-wave plates provide the birefringent needed to minimize ripple of output. The designed interleaver with two-stage interferometer in a 50 GHz channel spacing application exhibits a 0.5 dB passband and a 25 dB stopband both 27 GHz; a channel isolation higher than 35 dB and chromatic dispersion less than ±5 ps/nm within 0.5 dB passband; 1.3 dB insertion loss and 0.3 dB PDL; 0.04 GHz/°C thermal stability. Since all of the optical components can be optically bonded together, the device is robust and easy to be aligned, which reduces labor cost.

Effective thermo-optical enhanced cross-ring resonator MZI interleavers on SOI

A cross-ring (CR-) Mach-Zehnder interferometer (MZI) interleaver structure has been proposed and fabricated. It uses an '8' shaped cross-ring resonator to replace the conventional circular ring resonator. Thus, the new structure can have the function of add-signal. Furthermore, a thermo-optical fine tuning has been applied, which improves the crosstalk performance from approximately -10 dB to approximately -20 dB with 9 V applied on the heater of the 3-dB directional coupler.

Passive ring-assisted Mach-Zehnder interleaver on silicon-on-insulator

A passive ring-assisted Mach-Zehnder interferometer optical interleaver comprising a Y-bench, a 3-dB directional coupler, a ring-resonator, and a delay line is proposed. The interleaver is fabricated with 300 nm x 300 nm silicon wires on silicon-on-insulator. The fabricated interleaver demonstrates a flat-top spectral response. The measured free-spectral range is approximately 4 nm, the insertion loss is approximately -8 dB, and the crosstalk is <- 10 dB. Both the experimental and simulation results are in good agreement.

Proposed silicon wire interleaver structure

A Ring-resonator Mach-Zehnder interferometer (RR-MZI) optical interleaver structure comprising a ring resonator (RR) and a 3 dB directional coupler is proposed. The interleaver is fabricated with 300 nm x 300 nm silicon wires on silicon-on-insulator (SOI) wafers. The fabricated interleaver demonstrates a flat-top spectral response, and the measured free spectral range (FSR) is approximately 20 nm. The insertion loss (IL) of the device is approximately -10 dB and the polarization dependent loss (PDL) <5 dB. Both the experimental and simulation results are in good agreement.

Birefringent interleaver with a ring cavity as a phase-dispersion element

We propose and demonstrate a novel ring-cavity-based flat-top birefringent interleaver. A single ring cavity provides the two phase shifts needed, each for a polarization state, to achieve a flat-top spectral passband at the output. Fresnel reflectivities (for s- and p-polarization states) at the prism interface of the ring cavity are employed so that highly accurate thin-film coatings are not needed for the phase shifts. By choosing the appropriate incident angle near the Brewster angle, we can obtain the optimum interface reflectivities for flat passbands and extremely low cross talk. We also present the results of our experimental investigations of a flat-top 25-GHz optical interleaver that uses a novel ring cavity architecture. In a 25-GHz channel spacing application the interleaver exhibits a 0.5-dB passband larger than 0.14 nm (17.5 GHz), a 25-dB stopband greater than 0.14 nm (17.5 GHz), and channel isolation better than 28 dB over the entire C band.

Electro-optic Michelson Gires Tournois modulator for optical information processing and optical fiber communications

We propose and demonstrate an electro-optic modulator based on a Michelson interferometer with a Gires-Tournois etalon (GTE, or asymmetric Fabry-Perot etalon) in one of the two arms. The insertion of a GTE significantly reduces the required interaction length or the operation voltage. Our experimental and theoretical results agree well. An extension of our setup to a waveguide configuration can lead to practical modulators and switches with greater compactness and reduced operation voltage for optical fiber communications.