Journal Article

Silicon-chip-based ultrafast optical oscilloscope

Geraghty, David F., Salem, Reza, Turner-Foster, Amy C., Gaeta, Alexander L., Foster, Mark A., Lipson, Michal

2008

Overview

Scope for improvement The latest state-of-the-art oscilloscopes can achieve single-shot waveform measurements with a resolution of about 30 picoseconds. But ever greater telecommunication data rates and an expanding interest in ultrafast chemical and physical phenomena mean that there is now a demand for devices that measure optical waveforms with subpicosecond resolution. The sensitivity of conventional oscilloscopes is limited by the electronic bandwidth of photodetectors and circuits. Now Foster et al . demonstrate an all-optical method for real-time measurement of temporal optical waveforms with a resolution a hundredfold higher than electronic techniques. The heart of the device is a silicon photonic chip made with the same materials and techniques as standard microprocessors but which manipulates photons instead of electrons. The potential integration of this device in microelectronics could produce an instrument that could be used in many branches of science where simple measurements of optical waveforms are required. With the realization of faster telecommunication data rates and an expanding interest in ultrafast chemical and physical phenomena, it has become important to develop techniques that enable simple measurements of optical waveforms with subpicosecond resolution 1 . State-of-the-art oscilloscopes with high-speed photodetectors provide single-shot waveform measurement with 30-ps resolution. Although multiple-shot sampling techniques can achieve few-picosecond resolution, single-shot measurements are necessary to analyse events that are rapidly varying in time, asynchronous, or may occur only once. Further improvements in single-shot resolution are challenging, owing to microelectronic bandwidth limitations. To overcome these limitations, researchers have looked towards all-optical techniques because of the large processing bandwidths that photonics allow. This has generated an explosion of interest in the integration of photonics on standard electronics platforms, which has spawned the field of silicon photonics 2 and promises to enable the next generation of computer processing units and advances in high-bandwidth communications. For the success of silicon photonics in these areas, on-chip optical signal-processing for optical performance monitoring will prove critical. Beyond next-generation communications, silicon-compatible ultrafast metrology would be of great utility to many fundamental research fields, as evident from the scientific impact that ultrafast measurement techniques continue to make 3 , 4 , 5 . Here, using time-to-frequency conversion 6 via the nonlinear process of four-wave mixing on a silicon chip, we demonstrate a waveform measurement technology within a silicon-photonic platform. We measure optical waveforms with 220-fs resolution over lengths greater than 100 ps, which represent the largest record-length-to-resolution ratio (>450) of any single-shot-capable picosecond waveform measurement technique 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 . Our implementation allows for single-shot measurements and uses only highly developed electronic and optical materials of complementary metal-oxide-semiconductor (CMOS)-compatible silicon-on-insulator technology and single-mode optical fibre. The mature silicon-on-insulator platform and the ability to integrate electronics with these CMOS-compatible photonics offer great promise to extend this technology into commonplace bench-top and chip-scale instruments.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: Applied sciences / Capacity / Design. Technologies. Operation analysis. Testing / Electronics / Exact sciences and technology / Fundamental areas of phenomenology (including applications) / Humanities and Social Sciences / Integrated circuits / letter / Measurement / Measurement techniques / Methods / multidisciplinary / Nonlinear optics / Optical properties / Optical telecommunications / Optics / Oscilloscopes / Physics / Science / Science (multidisciplinary) / Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices / Silicon / Telecommunications / Telecommunications and information theory / Ultrafast processes; optical pulse generation and pulse compression / Waveforms