Albert Michaeli

Flatband slow light in photonic crystals featuring spatial pulse compression and terahertz bandwidth.

Paradoxically, slow light promises to increase the speed of telecommunications in novel photonic structures, such as coupled resonators [1] and photonic crystals [2,3]. Apart from signal delays, the key consequence of slowing light down is the enhancement of light-matter interactions. Linear effects such as refractive index modulation scale linearly with slowdown in photonic crystals [3], and nonlinear effects are expected to scale with its square [4]. By directly observing the spatial compression of an optical pulse, by factor 25, we confirm the mechanism underlying this square scaling law. The key advantage of photonic structures over other slow light concepts is the potentially large bandwidth, which is crucial for telecommunications [5]. Nevertheless, the slow light previously observed in photonic crystals [2,3,6,7] has been very dispersive and featured narrow bandwidth. We demonstrate slow light with a bandwidth of 2.5 THz and a delay-bandwidth product of 30, which is an order of magnitude larger than any reported so far.

Coupled photonic crystal heterostructure nanocavities

We show the first experimental demonstration of multiple heterostructure photonic crystal cavities being coupled together to form a chain of coupled resonators with up to ten cavities. This system allows us to engineer the group velocity of light over a wide range. Devices were fabricated using 193 nm deep UV lithography and standard silicon processing technology. Structures were analysed using both coupled resonator and photonic bandstructure theory, and we highlight the discrepancies arising from subtle imperfections of the fabricated structure.

Low loss silicon on insulator photonic crystal waveguides made by 193nm optical lithography

We show the successful fabrication and operation of photonic crystal waveguides on SOI, with lower silicon dioxide cladding remaining, using 193 nm DUV lithography. We demonstrate that 193 nm lithography gives more process latitude, allowing a wider range of periods and hole diameters to be printed, as well as reducing the optical proximity effect to a minimum. The smallest period /hole size variation printed successfully was 280 nm and 150 nm, which is very promising for ambitious future designs. Lowest losses obtained were 14.2 +/- 2.0 dB/cm for a W1 waveguide in a 400 nm lattice with an r/a of 0.25 at a frequency of 0.257 a/lambda, which approaches the best losses reported for air-bridge type W1s.

Integrated silicon photonics for optical networks [Invited]

Feature Issue on Nanoscale Integrated Photonics for Optical Networks Fiber optic communication is well established today in long-haul, metro, and some data communication segments. Optical technologies continue to penetrate more into the network owing to the increase in bandwidth demands; however, they still suffer from too expensive solutions. Silicon photonics is a new technology developing integrated photonic devices and circuits based on the unique silicon material that has already revolutionized the face of our planet through the microelectronics industry. This paper reviews silicon photonics technology at Intel, showing how using the same mature, low-cost silicon CMOS technology we develop many of the building blocks required in current and future optical networks. After introducing the silicon photonics motivation for networks, we discuss the various devices--waveguides, modulators, Raman amplifiers and lasers, photodetectors, optical interconnects, and photonic crystals--from the points of view of applications, principle of operation, process development, and performance results.

Tailoring the spectral response of add/drop single and multiple resonators in silicon-on-insulator

Channel dropping waveguide filters based on single and multiple resonators in silicon-on-insulator (SOI) technology are of great interest due to their compactness and high wavelength selectivity, which is a desirable feature for photonic modulators, detectors, and other optically integrated components in telecommunication systems, in particular for wavelength division multiplexing (WDM) systems. Particular advantage of these filters is that they are capable of producing relatively large free spectral range (FSR) as well as narrow 3-dB bandwidth of the filter resonances. Herein we report experimental results and discuss the possibility of designing mono-mode and (nearly) polarization independent SOI ring and racetrack resonators with the FSR in excess of 30 nm.

Tailoring the response and temperature characteristics of multiple serial-coupled resonators in silicon on insulator

Silicon-on-Insulator (SOI) has emerged as promising material choice for various integrated optoelectronic devices. Two issues make SOI attractive for complex optical systems: the cost reduction due to compatibility with CMOS technology and high refractive index contrast between core and cladding, which is an important property for good confinement of light and efficient guiding and coupling in sub-micron waveguides. However, for those devices that are intended to be part of broadband optical networks, for example multiplexers and de-multiplexers, it is desirable to demonstrate a high selectivity and a tunable response. Thus, it is necessary to provide wavelength selective elements with the ability to filter input data streams producing a large Free Spectral Range (FSR), a small Full Width at Half Maximum (FWHM), and a high quality factor (Q), all conditions set by communication standards. Owing to the generic and adaptable operation, ring-resonator-types of filters in SOI are often considered as candidates to meet these demands. Herein two different designs are investigated from both experimental and modelling standpoints in order to tailor the filter transfer function. These are mutually coupled (Vernier) resonators and cascaded resonators based on small SOI photonic wires. Fabricated filters designed to provide a large FSR and a polarisation independent (PI) response are analysed and improvements proposed. Issues associated with temperature control of the transfer function have also been addressed.

Optical filters in silicon-on-insulator: design considerations for devices based upon strip and rib waveguides

The transfer function of a photonic filter is significantly influenced by the profile of the waveguides forming the device. In this work we discuss requirements for devices based on two geometries, rib and wire shaped waveguides in Silicon-on-Insulator, from both the modal and polarisation standpoints. General guidelines and recommendations for the design of single-mode and polarisation-independent ring resonator filters with large Free Spectral Range (>30nm) are given, together with supportive experimental results.

Flatband Slow Light in Photonic Crystal Waveguides

A photonic crystal waveguide that features slow light without noticeable dispersion is demonstrated using a higher order even mode in a W2 waveguide on a SOI platform.

Small Optical Filters in Silicon-on-Insulator

Single mode, polarisation independent filters with large free spectral range are basic requirements for optical networks. In this paper we discuss (with experimental results) the possibility of establishing such devices upon small strip waveguides in silicon-on-insulator (SOI)

Photonic crystal development using 193 nm optical lithography

We report photonic crystal designs fabricated in silicon on insulator wafers using 248 nm and 193 nm deep-UV lithography. This work was carried out using standard CMOS equipment and processes in an Intel fab.