F. Gan

Maximizing the Thermo-Optic Tuning Range of Silicon Photonic Structures

We demonstrate 20 nm thermo-optic tuning in silicon microring resonators with 16 nm free spectral range (FSR), the largest reported full-FSR thermal tuning, with a tuning efficiency of 28 muW/GHz, enabling telecom microphotonic tunable filters.

CMOS-compatible dual-output silicon modulator for analog signal processing.

A broadband, Mach-Zehnder-interferometer based silicon optical modulator is demonstrated, with an electrical bandwidth of 26 GHz and V(pi)L of 4 V.cm. The design of this modulator does not require epitaxial overgrowth and is therefore simpler to fabricate than previous devices with similar performance.

All silicon infrared photodiodes: photo response and effects of processing temperature

CMOS compatible infrared waveguide Si photodiodes are made responsive from 1100 to 1750 nm by Si(+) implantation and annealing. This article compares diodes fabricated using two annealing temperatures, 300 and 475 degrees C. 0.25-mm-long diodes annealed to 300 degrees C have a response to 1539 nm radiation of 0.1 A W-(-1) at a reverse bias of 5 V and 1.2 A W(-1) at 20 V. 3-mm-long diodes processed to 475 degrees C exhibited two states, L1 and L2, with photo responses of 0.3 +/-0.1 A W(-1) at 5 V and 0.7 +/-0.2 A W(-1) at 20 V for the L1 state and 0.5 +/-0.2 A W(-1) at 5 V and 4 to 20 A W(-1)-1 at 20 V for the L2 state. The diodes can be switched between L1 and L2. The bandwidths vary from 10 to 20 GHz. These diodes will generate electrical power from the incident radiation with efficiencies from 4 to 10 %.

Photonic Analog-to-Digital Conversion with Electronic-Photonic Integrated Circuits

Photonic Analog-to-Digital Conversion (ADC) has a long history. The premise is that the superior noise performance of femtosecond lasers working at optical frequencies enables us to overcome the bottleneck set by jitter and bandwidth of electronic systems and components. We discuss and demonstrate strategies and devices that enable the implementation of photonic ADC systems with emerging electronic-photonic integrated circuits based on silicon photonics. Devices include 2-GHz repetition rate low noise femtosecond fiber lasers, Si-Modulators with up to 20 GHz modulation speed, 20 channel SiN-filter banks, and Ge-photodetectors. Results towards a 40GSa/sec sampling system with 8bits resolution are presented.

Electronic Photonic Integrated Circuits for High Speed, High Resolution, Analog to Digital Conversion

Progress in developing high speed ADCs occurs rather slowly - at a resolution increase of 1.8 bits per decade. This slow progress is mostly caused by the inherent jitter in electronic sampling - currently on the order of 250 femtoseconds in the most advanced CMOS circuitry. Advances in femtosecond lasers and laser stabilization have led to the development of sources of ultrafast optical pulse trains that show jitter on the level of a few femtoseconds over the time spans of typical sampling windows and can be made even smaller. The MIT-GHOST (GigaHertz High Resolution Optical Sampling Technology) Project funded under DARPAs Electronic Photonic Integrated Circuit (EPIC) Program is trying to harness the low noise properties of femtosecond laser sources to overcome the electronic bottleneck inherently present in pure electronic sampling systems. Within this program researchers from MIT Lincoln Laboratory and MIT Campus develop integrated optical components and optically enhanced electronic sampling circuits that enable the fabrication of an electronic-photonic A/D converter chip that surpasses currently available technology in speed and resolution and opens up a technology development roadmap for ADCs. This talk will give an overview on the planned activities within this program and the current status on some key devices such as wavelength-tunable filter banks, high-speed modulators, Ge photodetectors, miniature femtosecond-pulse lasers and advanced sampling techniques that are compatible with standard CMOS processing.

Low Power Thermal Tuning of Second-order Microring Resonators

Efficient thermal tuning of 36 pm/K and 60 muW/GHz is shown for high-index-contrast silicon nitride second-order filters. Their compact size, large free-spectral range, low tuning power, and silicon compatibility make these resonators attractive for photonic integration.

Erbium Doped Silicon for Light Emitting Devices

We report on the excitation and de-excitation processes of erbium implanted in silicon and the integration of Si:Er light emitting devices (LED) with standard CMOS technology. We find two deexcitation processes, an Auger process below 100 K and a phonon mediated energy backtransfer above 100 K. We present the first optical voice link with a silicon LED as the emitter. Optical transmission system performance with our LED is possible below 200 K.

High Speed Analog-to-Digital Conversion with Silicon Photonics

Sampling rates of high-performance electronic analog-to-digital converters (ADC) are fundamentally limited by the timing jitter of the electronic clock. This limit is overcome in photonic ADCs by taking advantage of the ultra-low timing jitter of femtosecond lasers. We have developed designs and strategies for a photonic ADC that is capable of 40 GSa/s at a resolution of 8 bits. This system requires a femtosecond laser with a repetition rate of 2 GHz and timing jitter less than 20 fs. In addition to a femtosecond laser this system calls for the integration of a number of photonic components including: a broadband modulator, optical filter banks, and photodetectors. Using silicon-on-insulator (SOI) as the platform we have fabricated these individual components. The silicon optical modulator is based on a Mach-Zehnder interferometer architecture and achieves a VπL of 2 Vcm. The filter banks comprise 40 second-order microring-resonator filters with a channel spacing of 80 GHz. For the photodetectors we are exploring ion-bombarded silicon waveguide detectors and germanium films epitaxially grown on silicon utilizing a process that minimizes the defect density.

Silicon Electronic Photonic Integrated Circuits for High Speed Analog to Digital Conversion

Integrated optical components on the silicon platform and optically enhanced electronic sampling circuits are demonstrated that enable the fabrication of a variety of electronic-photonic A/D converter chips surpassing currently available technology in sampling speed and resolution

Integrated Optical Components in Silicon for High Speed Analog-to- Digital Conversion

Advances in femtosecond lasers and laser stabilization have led to the development of sources of ultrafast optical pulse trains that show jitter on the level of a few femtoseconds over tens of milliseconds and over seconds if referenced to atomic frequency standards. These low jitter sources can be used to perform opto-electronic analog to digital conversion that overcomes the bottleneck set by electronic jitter when using purely electronic sampling circuits and techniques. Electronic Photonic Integrated Circuits (EPICs) may enable in the near future to integrate such an opto-electronic analog-to-digital converters (ADCs) completely. This presentation will give an overview of integrated optical devices such as low jitter lasers, electro-optical modulators, Si-based filter banks, and high-speed Si-photodetectors that are compatible with standard CMOS processing and which are necessary for the implementation of EPIC-chips for advanced opto-electronic ADCs.