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Modulation Linearity Characterization of Si Ring Modulators
Modulation linearity of Si ring modulators (RMs) is investigated through the numerical simulation based on the coupled-mode theory and experimental verification. Numerical values of the key parameters needed for the simulation are experimentally extracted. Simulation and measurement results agree well. With these, the influence of input optical wavelength and power on the Si RM linearity are characterized.
Si photonic-electronic monolithically integrated optical receiver with a built-in temperature-controlled wavelength filter
We present a Si photonic-electronic integrated ring-resonator based optical receiver that contains a temperature-controlled ring-resonator filter (RRF), a Ge photodetector, and receiver circuits in a single chip. The temperature controller automatically determines the RRF temperature at which the maximum transmission of the desired WDM signal is achieved and maintains this condition against any temperature or input wavelength fluctuation. This Si photonic-electronic integrated circuit is realized with 0.25-µm photonic BiCMOS technology, and its operation is successfully confirmed with measurement.
Silicon-organic hybrid photonics: Overview of recent advances, electro-optical effects and CMOS-integration concepts
In recent decades, much research effort has been invested in the development of photonic integrated circuits, and silicon-on-insulator technology has been established as a reliable platform for highly scalable silicon-based electro-optical modulators. However, the performance of such devices is restricted by the inherent material properties of silicon. An approach to overcoming these deficiencies is to integrate organic materials with exceptionally high optical nonlinearities into a silicon-on-insulator photonic platform. Silicon–organic hybrid photonics has been shown to overcome the drawbacks of silicon-based modulators in terms of operating speed, bandwidth, and energy consumption. This work reviews recent advances in silicon–organic hybrid photonics and covers the latest improvements to single components and device concepts. Special emphasis is given to the in-device performance of novel electro-optical polymers and the use of different electro-optical effects, such as the linear and quadratic electro-optical effect, as well as the electric-field-induced linear electro-optical effect. Finally, the inherent challenges of implementing non-linear optical polymers on a silicon photonic platform are discussed and a perspective for future directions is given.
From Lab-on-chip to Lab-in-App: Challenges towards silicon photonic biosensors product developments
This work presents and evaluates different approaches of integrated optical sensors based on photonic integrated circuit (PIC) technologies for refractive index sensing. Bottlenecks in the fabrication flow towards an applicable system are discussed that hinder a cost-effective mass-production for disposable sensor chips. As sensor device, a waveguide coupled micro-ring based approach is chosen which is manufactured in an 8” wafer level process. We will show that the co-integration with a reproducible, scalable and low-cost microfluidic interface is the main challenge which needs to be overcome for future application of silicon technology based PIC sensor chips.
Design and performance analysis of integrated focusing grating couplers for the transverse-magnetic TM00 mode in a photonic BiCMOS technology
Focusing grating couplers for the excitation of the fundamental transverse-magnetic (TM) mode in integrated silicon photonic waveguides are designed and characterized under the boundary conditions of a photonic BiCMOS foundry. Two types of waveguide geometries are considered – a nanowire and a rib waveguide. Wafer-scale experimental results for nanowire TM grating couplers are in excellent agreement with numerical investigations and demonstrate a robust behavior on the wafer. The mean coupling loss and the 3s interval are -3.9 ± 0.3 dB. The on wafer variation is three times lower than for the fundamental transverse-electric (TE) polarization. Similarly, the coupling in rib waveguides is examined as well. The results indicate that the rib waveguides require a modified geometry when designed for TM. In general, the nanowire waveguide type is more suitable for TM coupling, showing a stable and repeatable performance. © 2020, The Author(s).
Cross-polarization effects in sheared 2D grating couplers in a photonic BiCMOS technology
We investigate numerically and experimentally sheared 2D grating couplers in a photonic BiCMOS technology with a focus on their splitting behavior. Two realization forms of a waveguide-To-grating shear angle are considered. The cross-polarization used as a figure-of-merit is shown to be strongly dependent on the grating perturbation strength and is a crucial limitation not only for the grating splitting performance, but also for its coupling efficiency. © 2020 The Japan Society of Applied Physics.
On-Chip Dispersion Measurement of the Quadratic Electro-Optic Effect in Nonlinear Optical Polymers Using a Photonic Integrated Circuit Technology
A novel method to determine the dispersion of the quadratic electro-optic effect in nonlinear optical materials by using a silicon-on-insulator microring resonator is presented. The microring consists of a silicon slot waveguide enabling large dc electric field strength at low applied voltages. The dispersion of third-order hyperpolarizability of a linear conjugated dye is approximated by using a two-level model for the off-resonant spectral region. As an example, the dispersion of the resonance wavelength of the resonator filled with a dye doped polymer was measured in dependence of the applied dc voltage. The polymer was poly (methylmethacrylate) doped with 5 wt% disperse red 1 (DR1), and the measurements have been carried out at the telecommunication wavelength band around 1550 nm (optical C-band). The described measurements represent a new technique to determine the dispersion of the third-order susceptibility and molecular hyperpolarizability of the material filled into the slot of the ring-resonator. © 2019 IEEE.
A physical origin of cross-polarization and higher-order modes in two-dimensional (2D) grating couplers and the related device performance limitations
We explore scattering effects as the physical origin of cross-polarization and higher-order modes in silicon photonic 2D grating couplers (GCs). A simplified analytical model is used to illustrate that in-plane scattering always takes place, independent of grating geometry and design coupling angle. Experimental investigations show furthermore that grating design parameters are especially related to the modal composition of both the target- and the cross-polarization. Scattering effects and the associated cross-polarization and higher-order modes are indicated as the main reason for the higher 2D GC insertion loss compared to standard 1D GCs. In addition, they can be responsible for a variable 2D GC spectrum shape, bandwidth and polarization dependent loss.
Direct observation and simultaneous use of linear and quadratic electro-optical effects
We report on the direct observation and simultaneous use of the linear and quadratic electro-optical effect and propose a method by which higher-order susceptibilities of electro-optical materials can be determined. The evaluation is based on the separation of the second- and third-order susceptibilities and the experimental technique uses a slot waveguide ring resonator fabricated in integrated photonic circuit technology, which is embedded by a guest-host polymer system consisting of the azobenzene dye Disperse Red 1 in a poly(methyl methacrylate) matrix as an active electro-optical material. The contribution of both effects on the electro-optical response under the influence of static and time-varying electrical fields is investigated. We show that the quadratic electro-optical effect has a significant influence on the overall electro-optical response even with acentric molecular orientated molecules. Our findings have important implications for developing electro-optical devices based on polymer-filled slot waveguides and give rise to advanced photonic circuits. © 2020 IOP Publishing Ltd.
CMOS-Compatible Silicon Photonic Sensor for Refractive Index Sensing Using Local Back-Side Release
Silicon photonic sensors are promising candidates for lab-on-a-chip solutions with versatile applications and scalable production prospects using complementary metal-oxide semiconductor (CMOS) fabrication methods. However, the widespread use has been hindered because the sensing area adjoins optical and electrical components making packaging and sensor handling challenging. In this work, a local back-side release of the photonic sensor is employed, enabling a separation of the sensing area from the rest of the chip. This approach allows preserving the compatibility of photonic integrated circuits in the front-end of line and metal interconnects in the back-end of line. The sensor is based on a micro-ring resonator and is fabricated on wafer-level using a CMOS technology. We revealed a ring resonator sensitivity for homogeneous sensing of 106 nm/RIU. © 1989-2012 IEEE.