Tolerant, broadband tunable 2 × 2 coupler circuit

We propose a circuit design for a broadband tunable 2 x 2 waveguide coupler, consisting of a two-stage Mach-Zehnder interferometer with electro-optic phase shifters in each stage. We demonstrate that such design can be configured as a tunable coupler with arbitrary coupling ratio and with a uniform response over 50-nm spectral range around 1550 nm. The design is also tolerant to fabrication variations that affect the coupling ratios of the directional couplers

Interleavers

The chapter describes principles, analysis, design, properties, and implementations of optical frequency (or wavelength) interleavers. The emphasis is on finite impulse response devices based on cascaded Mach-Zehnder-type filter elements with carefully designed coupling ratios, the so-called resonant couplers. Another important class that is discussed is the infinite impulse response type, based on e.g. Fabry-Perot, Gires-Tournois, or ring resonators

Automatic Tuning of Silicon Photonics Millimeter-Wave Transceivers Building Blocks

Today, continuously growing wireless traffic have guided the progress in the wireless communication systems. Now, evolution towards next generation (5G) wireless communication systems are actively researched to accommodate expanding future data traffic. As one of the most promising candidates, integrating photonic devices in to the existing wireless system is considered to improve the performance of the systems. Emerging silicon photonic integrated circuits lead this integration more practically, and open new possibilities to the future communication systems. In this dissertation, the development of the electrical wireless communication systems are briefly explained. Also, development of the microwave photonics and silicon photonics are described to understand the possibility of the hybrid SiP integrated wireless communication systems. A limitation of the current electrical wireless systems are addressed, and hybrid integrated mm-wave silicon photonic receiver, and silicon photonic beamforming transmitter are proposed and analyzed in system level. In the proposed mm-wave silicon photonic receiver has 4th order pole-zero silicon photonic filter in the system. Photonic devices are vulnerable to the process and temperature variations. It requires manual calibration, which is expensive, time consuming, and prone to human errors. Therefore, precise automatic calibration solution with modified silicon photonic filter structure is proposed and demonstrated. This dissertation demonstrates fully automatic tuning of silicon photonic all-pass filter (APF)-based pole/zero filters using a monitor-based tuning method that calibrates the initial response by controlling each pole and zero individually via micro-heaters. The proposed tuning approach calibrates severely degraded initial responses to the designed elliptic filter shapes and allows for automatic bandwidth and center frequency reconfiguration of these filters. This algorithm is demonstrated on 2nd- and 4th-order filters fabricated in a standard silicon photonics foundry process. After the initial calibration, only 300ms is required to reconfigure a filter to a different center frequency. Thermal crosstalk between the micro-heaters is investigated, with substrate thinning demonstrated to suppress this effect and reduce filter calibration to less than half of the original thick substrate times. This fully automatic tuning approach opens the possibility of employing silicon photonic filters in real communication systems. Also, in the proposed beamforming transmitter, true-time delay ring resonator based 1x4 beamforming network is imbedded. A proposed monitor-based tuning method compensates fabrication variations and thermal crosstalk by controlling micro-heaters individually using electrical monitors. The proposed tuning approach successfully demonstrated calibration of OBFN from severely degraded initial responses to well-defined group delay response required for the targeted radiating angle with a range of 60◦ (-30◦ to 30◦ ) in a linear beamforming antenna array. This algorithm is demonstrated on OBFN fabricated in a standard silicon photonics foundry process. The calibrated OBFN operates at 30GHz and provide 2GHz bandwidth. This fully automatic tuning approach opens the possibility of employing silicon OBFN in real wideband mm-wave wireless communication systems by providing robust operating solutions. All the proposed photonic circuits are implemented using the standard silicon photonic technologies, and resulted in several publications in IEEE/OSA Journals and Conferences

MEMS-enabled silicon photonic integrated devices and circuits

Photonic integrated circuits have seen a dramatic increase in complexity over the past decades. This development has been spurred by recent applications in datacenter communications and enabled by the availability of standardized mature technology platforms. Mechanical movement of wave-guiding structures at the micro- and nanoscale provides unique opportunities to further enhance functionality and to reduce power consumption in photonic integrated circuits. We here demonstrate integration of MEMS-enabled components in a simplified silicon photonics process based on IMEC's Standard iSiPP50G Silicon Photonics Platform and a custom release process

Widely tunable silicon Raman laser

Stimulated Raman scattering is an effective means of wavelength conversion and can largely extend the operating spectral range of an optical source. We demonstrate a highperformance tunable Raman laser on a sub-micrometer-thick silicon on insulator wafer using a standard foundry process. The key feature to this laser is the use of a tunable coupling mechanism to adjust both pump and signal coupling coefficients in the ring cavity, allowing demonstration of laser emission over a large wavelength tuning range of 83 nm. This Raman laser demonstrates efficient (slope of up to 26% and a maximum pump-to-signal power conversion efficiency of 10%) on-chip non-linear wavelength conversion. Our results indicate great promise for substantially increasing the optical spectral resources available on a silicon chip

Monolithic integration of semiconductor ring lasers

The interest in semiconductor ring lasers (SRLs) has been steadily growing in the last few years because of several unique properties such as ultrafast directional bistability, stable single mode operation and potential for integration. However, most of the mode dynamical behavior as well as the optimum device design are still far from a complete understanding. This thesis reports on the design, technological development and characterization of SRLs emitting at 1.55 um, which are monolithically integrated with a number of other optical elements such as tunable couplers, optical amplifiers, Bragg reflectors and distributed feedback lasers (DFBs). A detailed analysis on the device design is presented with particular emphasis on its robustness with respect to fabrication tolerances and to the optical feedback from the output waveguides. The complete processing technology is developed with a focus on selective dry etching to achieve very accurate control of the waveguide bending losses. Three completely novel and monolithically integrated SRL devices are fabricated and characterized. The first is a master-slave device based on the monolithic integration of an SRL with a DFB that shows highly efficient cavity enhanced four-wave mixing up to detuning frequencies of 1.5 THz. In a second geometry, a Bragg reflector defined on one of the output waveguides selects the lasing mode of the SRL. The device shows world-record wavelength switching speeds as low as 450 ps and strong immunity to thermal fluctuations of the grating. The third device is an SRL with tunable couplers for active Q-switching applications. Pulses as short as 120 ps at a repetition rate of 1.8 GHz are obtained by injecting only a few mA of current into the tuning section

Tunable Optical Filters Using Compound Ring Resonators for DWDM

The device is based on a loop mirror in a ring resonator. The loop mirror allows tuning by changing the coupling coefficient of a directional coupler. The loop mirror is implemented using a Sagnac configuration to have the same optical path between the signals to be interfered (copropagating and counterpropagating ones). The filter structure allows optical integration for having higher free-spectral ranges. Simple design equations for the filter parameters and the tuning are reported. Measurements on a passive optical fiber tunable filter are presented. There is a good agreement between measurements and theory.Publicad

Programmable True Time Delay Lines Using Integrated Waveguide Meshes

[EN] We analyze and explore the potential that waveguide-mesh-based architectures used in programmable photonic integrated circuits can be configured to enable true time optical delay lines, which can find applications in different microwave photonics functionalities, such as beamforming and optical filtering. We also propose and experimentally demonstrate an alternative standalone tunable basic unit (TBU) architecture where its internal coupling device is implemented by means of a dual-drive tunable directional coupler (DD-TDC) that performs independent amplitude beam splitting and phase shifting. Compared to the previous alternatives based on 3-dB balanced Mach-Zehnder interferometers, the DD-TDC reduces by more than two times the insertion losses of TBUs enabling the potential realization of larger meshes with a three-fold enhanced step-time resolution. Bandwidth and robustness analysis are also considered.This work was supported in part by the European Research Council under Grant ERC-ADG-2016-471715 UMWP-CHIP, in part by the COST Action CA16220 EUWMP, in part by the Spanish MINECO Projects TEC2014-60378-C2-1-R, and in part by the Gen. Valenciana PROMETEO Project 2017/103.Pérez-López, D.; Sánchez-Gomáriz, E.; Capmany Francoy, J. (2018). Programmable True Time Delay Lines Using Integrated Waveguide Meshes. Journal of Lightwave Technology. 36(19):4591-4601. https://doi.org/10.1109/JLT.2018.283100845914601361