Silicon optical modulators

Abstract

Optical technology is poised to revolutionise short reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such interconnect is the optical modulator. Modulators have been improved dramatically in recent years. Most notably the bandwidth has increased from the MHz to the multi GHz regime in little more than half a decade. However, the demands of optical interconnect are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics.Minimising metrics such as the energy per bit, and device footprint, whilst maximising bandwidth and modulation depth are non trivial demands. All of this must be achieved with acceptable thermal tolerance and optical spectral width, using CMOS compatible fabrication processes. Here we discuss the techniques that have, and will, be used to implement silicon optical modulators, as well as the outlook for these devices, and the candidate solutions of the future.

A strong electro-optically active lead-free ferroelectric integrated on silicon

“…Meanwhile, the steadily improving performance of complementary metal oxide semiconductor (CMOS) technology increases the difficulty to handle inter-or intra-chip data communication by means of electrical wiring 10 because of power constraints in combination with increased bandwidth demands. In this context, devices working in the optical domain have emerged as a mature field of research 11 , and building blocks required for a functional photonic network such as detectors 12 or modulators 13 have already been integrated on Si. However, today's silicon photonics technology does not exploit the linear electro-optical (EO) properties available in oxides, which for decades fuelled the progress in telecommunication based on fibre optics to extremely high modulation speeds with well-established devices 14 .…”

High-density waveguide superlattices with low crosstalk

“…S ilicon photonics has made great strides in developing a wide range of devices [1][2][3][4][5][6][7][8][9][10][11][12][13] . Built upon these advances, this technology now offers a low-cost platform for building large-scale optical systems [14][15][16][17] .…”

Device engineering for silicon photonics

“…Performance comparable to that of carrier-accumulation-based modulators was achieved recently by the same group using an optimized design with a pre-emphasis driving signal [29]. Similar to the case for carrier-accumulation-based modulators, in which the speed is limited by the device resistance and capacitance, the speed of carrier-injectionbased modulators is limited by the minority carrier lifetime [2].…”

“…by application of strain). Th e refractive index change induced by the presence of free charge carriers, known as the plasma eff ect, has been generally used for making silicon optical modulators [2]. Th e plasma eff ect was systematically characterized by Soref and Bennett in 1987 [26].…”

“…Th ere is also a trend toward the fabrication of silicon-photonic devices through external foundries. Many interesting review articles on different fi elds of silicon photonics have been published recently and we would like to refer the readers to the reviews by Reed et al [2] on silicon optical modulators; the review by Liang et al [3] on lasers and other recent reviews on germanium-based integrated photodetectors and silicon optical nonlinear eff ects [4,5].…”