Jelena Notaros

Ultra-efficient CMOS fiber-to-chip grating couplers

Apodized bi-level fiber-to-chip grating couplers, designed using a complex-wavevector band-structure approach, are demonstrated in a commercially available, monolithic SOI CMOS process achieving 92% (-0.36dB) coupling efficiency.

Finite-difference complex-wavevector band structure solver for analysis and design of periodic radiative microphotonic structures

We demonstrate a finite-difference approach to complex-wavevector band structure simulation and its use as a tool for the analysis and design of periodic leaky-wave photonic devices. With the (usually real) operating frequency and unit-cell refractive index distribution as inputs, the eigenvalue problem yields the complex-wavevector eigenvalues and Bloch modes of the simulated structure. In a two-dimensional implementation for transverse-electric fields with radiation accounted for by perfectly matched layer boundaries, we validate the method and demonstrate its use in simulating the complex-wavevector band structures and modal properties of a silicon photonic crystal waveguide, an array-antenna-inspired grating coupler with unidirectional radiation, and a recently demonstrated low-loss Bloch-mode-based waveguide crossing array. Additionally, we show the first direct solution of the recently proposed open-system low-loss Bloch modes. We expect this method to be a valuable tool in photonics design, enabling the rigorous analysis and synthesis of advanced periodic and quasi-periodic photonic devices.

Accurate electromagnetic modeling of melting hail

Analysis of electromagnetic scattering from hailstones has conventionally been done using the T-matrix method. This method, which reduces exactly to the Lorenz-Mie scattering theory when the scattering particle is a homogeneous or layered piecewise homogeneous sphere, worked well so far when we tried to understand the measurements. However the measurements have become fairly sophisticated with many decades of multiple polarization measurements and the current models are not able to explain many of the nuances in the measurements, because the current model is not well suited for analysis of arbitrarily shaped and non-layered particles.

Programmable dispersion on a photonic integrated circuit for classical and quantum applications

We demonstrate a large-scale tunable-coupling ring resonator array, suitable for high-dimensional classical and quantum transforms, in a CMOS-compatible silicon photonics platform. The device consists of a waveguide coupled to 15 ring-based dispersive elements with programmable linewidths and resonance frequencies. The ability to control both quality factor and frequency of each ring provides an unprecedented 30 degrees of freedom in dispersion control on a single spatial channel. This programmable dispersion control system has a range of applications, including mode-locked lasers, quantum key distribution, and photon-pair generation. We also propose a novel application enabled by this circuit - high-speed quantum communications using temporal-mode-based quantum data locking - and discuss the utility of the system for performing the high-dimensional unitary optical transformations necessary for a quantum data locking demonstration.

Accurate and efficient full-wave electromagnetic analysis of scattering from hailstones

Numerically rigorous full-wave electromagnetic analysis of scattering from hailstones based primarily on the method of moments is presented. The analysis employs generalized curved hexahedral volume and surface elements of arbitrary geometrical-mapping orders, current polynomial vector basis functions of arbitrarily high expansion orders, and higher order modeling of inhomogeneous lossy dielectric materials. The method can accurately and efficiently model and analyze scattering from dry, wet, and melting hailstones of various realistic shapes and material compositions, including layered models and continuous variations of the dielectric permittivity.

Integrated rare-Earth doped mode-locked lasers on a CMOS platform

Mode-locked lasers provide extremely low jitter optical pulse trains for a number of applications ranging from sampling of RF-signals and optical frequency combs to microwave and optical signal synthesis. Integrated versions have the advantage of high reliability, low cost and compact. Here, we describe a fully integrated mode-locked laser architecture on a CMOS platform that utilizes rare-earth doped gain media, double-chirped waveguide gratings for dispersion compensation and nonlinear Michelson Interferometers for generating an artificial saturable absorber to implement additive pulse mode locking on chip. First results of devices at 1.9 μm using thulium doped aluminum-oxide glass and operating in the Q-switched mode locking regime are presented.

Monolithically integrated erbium-doped tunable laser on a CMOS-compatible silicon photonics platform

A tunable laser source is a crucial photonic component for many applications, such as spectroscopic measurements, wavelength division multiplexing (WDM), frequency-modulated light detection and ranging (LIDAR), and optical coherence tomography (OCT). In this article, we demonstrate the first monolithically integrated erbium-doped tunable laser on a complementary-metal-oxide-semiconductor (CMOS)-compatible silicon photonics platform. Erbium-doped Al2O3 sputtered on top is used as a gain medium to achieve lasing. The laser achieves a tunability from 1527 nm to 1573 nm, with a >40 dB side mode suppression ratio (SMSR). The wide tuning range (46 nm) is realized with a Vernier cavity, formed by two Si3N4 microring resonators. With 107 mW on-chip 980 nm pump power, up to 1.6 mW output lasing power is obtained with a 2.2% slope efficiency. The maximum output power is limited by pump power. Fine tuning of the laser wavelength is demonstrated by using the gain cavity phase shifter. Signal response times are measured to be around 200 μs and 35 µs for the heaters used to tune the Vernier rings and gain cavity longitudinal mode, respectively. The linewidth of the laser is 340 kHz, measured via a self-delay heterodyne detection method. Furthermore, the laser signal is stabilized by continuous locking to a mode-locked laser (MLL) over 4900 seconds with a measured peak-to-peak frequency deviation below 10 Hz.

Publisher Correction: Integrating photonics with silicon nanoelectronics for the next generation of systems on a chip

In this Letter, owing to an error during the production process, the author affiliations were listed incorrectly. Affiliation number 5 (Colleges of Nanoscale Science and Engineering, State University of New York (SUNY)) was repeated, and affiliation numbers 6–8 were incorrect. In addition, the phrase “two oxide thickness variants” should have been “two gate oxide thickness variants”. These errors have all been corrected online.

Integrated optical phased arrays for quasi-Bessel-beam generation

Integrated optical phased arrays for generating quasi-Bessel beams are proposed and experimentally demonstrated in a CMOS-compatible platform. Owing to their elongated central beams, Bessel beams have applications in a range of fields, including multiparticle trapping and laser lithography. In this Letter, continuous Bessel theory is manipulated to formulate the phase and amplitude conditions necessary for generating free-space-propagating Bessel-Gauss beams using on-chip optical phased arrays. Discussion of the effects of select phased array parameters on the generated beams figures of merit is included. A one-dimensional splitter-tree-based phased array architecture is modified to enable arbitrary passive control of the arrays element phase and amplitude distributions. This architecture is used to experimentally demonstrate on-chip quasi-Bessel-beam generation with a ∼14  mm Bessel length and ∼30  μm power full width at half maximum.

Monolithic silicon photonics in a sub-100nm SOI CMOS microprocessor foundry: progress from devices to systems

We review recent progress of an effort led by the Stojanović (UC Berkeley), Ram (MIT) and Popović (CU Boulder) research groups to enable the design of photonic devices, and complete on-chip electro-optic systems and interfaces, directly in standard microelectronics CMOS processes in a microprocessor foundry, with no in-foundry process modifications. This approach allows tight and large-scale monolithic integration of silicon photonics with state-of-the-art (sub-100nm-node) microelectronics, here a 45nm SOI CMOS process. It enables natural scale-up to manufacturing, and rapid advances in device design due to process repeatability. The initial driver application was addressing the processor-to-memory communication energy bottleneck. Device results include 5Gbps modulators based on an interleaved junction that take advantage of the high resolution of the sub-100nm CMOS process. We demonstrate operation at 5fJ/bit with 1.5dB insertion loss and 8dB extinction ratio. We also demonstrate the first infrared detectors in a zero-change CMOS process, using absorption in transistor source/drain SiGe stressors. Subsystems described include the first monolithically integrated electronic-photonic transmitter on chip (modulator+driver) with 20-70fJ/bit wall plug energy/bit (2-3.5Gbps), to our knowledge the lowest transmitter energy demonstrated to date. We also demonstrate native-process infrared receivers at 220fJ/bit (5Gbps). These are encouraging signs for the prospects of monolithic electronics-photonics integration. Beyond processor-to-memory interconnects, our approach to photonics as a “More-than- Moore” technology inside advanced CMOS promises to enable VLSI electronic-photonic chip platforms tailored to a vast array of emerging applications, from optical and acoustic sensing, high-speed signal processing, RF and optical metrology and clocks, through to analog computation and quantum technology.