Abdelsalam A. Aboketaf

Controlled storage of light in silicon cavities.

We experimentally demonstrate a tunable delay element that is inherently insensitive to free-carrier loss and achieves up to 300ps of delay. It is capable of arbitrarily storing and releasing a pulse of light through dynamic tuning of a system of microcavities. The inherent storage time is more than 32 times the duration of the stored pulse.

Optical time division multiplexer on silicon chip.

In this work, we experimentally demonstrate a novel broadband optical time division multiplexer (OTDM) on a silicon chip. The fabricated devices generate 20 Gb/s and 40 Gb/s signals starting from a 5 Gb/s input signal. The proposed design has a small footprint of 1mm x 1mm. The system is inherently broadband with a bandwidth of over 100nm making it suitable for high-speed optical networks on chip.

A passively mode-locked quantum-dot laser operating over a broad temperature range

Broad temperature operation is demonstrated from 20 to 110 °C in a 5-GHz monolithic two-section InAs/GaAs quantum dot passively mode-locked laser with an optimized absorber to gain section length ratio of 0.11. Stable pulses of less than 19 ps full-width-half-maximum are measured over this entire temperature range. For a grounded absorber, mode-locking from the ground-state occurred over the range 20–92 °C, dual-mode lasing involving both ground and excited states from 93 to 98 °C and exclusively from the excited-state from 99 to 110 °C. The observed broad temperature operation agrees with theoretical analysis based on measured gain and absorption data that predicted improved temperature performance for a short absorber. The results are promising for the development of temperature-insensitive pulsed sources for uncooled applications such as data multiplexing and optical clocking.

Single photon adiabatic wavelength conversion

Adiabatic wavelength conversion is experimentally demonstrated at a single photon power-level using an integrated silicon ring resonator. This approach allows conversion of a photon to arbitrary wavelengths with no energy or phase matching constraints. The conversion is inherently low-noise and efficient with greater than 10% conversion efficiencies for wavelength changes up to 0.5 nm, more than twenty times the resonators line-width. The observed wavelength change and efficiency agrees well with theory and bright coherent light demonstrations. These results will enable integrated quantum optical wavelength conversion for application ranging from wavelength-multiplexed quantum networks to frequency bin entanglement.

Hybrid OTDM and WDM for multicore optical communication

In this work we propose a high-speed hybrid optical-time-division-multiplexing (OTDM) and wavelength-division-multiplexing (WDM) system that seamlessly generates high bit-rate data (>;200Gbit/s) from a low speed (5Gbit/s) quantum-dot mode locked laser pulse train. The high-speed output data can be generated using electro-optical micro-ring modulators that operate as low as (5Gbit/s). By utilizing time and wavelength domains, the proposed design is a promising solution for high-speed, compact and low-power consumption optical networks on chip.

Robust phase-shift-keying Silicon photonic modulator

Here we propose a robust silicon modulator that seamlessly generates phase shift keyed data. The modulator has very low insertion loss and is robust against electrical amplitude variations in the modulating signal; specifically a 50%-200% variation in modulating amplitude leads to only a π/9 variation in output optical phase, corresponding to only ± 10% variation in the differentially detected signal. This yields a ~2.5dB enhancement in SNR over OOK (on-off-keying) formats.

Passively mode-locked InAs quantum dot lasers on a silicon substrate by Pd-GaAs wafer bonding

We demonstrate an electrically pumped InAs quantum dot (QD) two-section passively mode-locked laser (MLL) on a silicon substrate by low temperature (250 °C) Pd-GaAs wafer bonding technology. The saturable absorber of the QD-MLL is electrically isolated by a 15-μm wide dry-etching gap which resulted in ∼30 kΩ resistance from the gain regions of the MLL. At room temperature, the laser operates in the O-band (1.3 μm) telecommunication wavelength regime with a threshold current of 94 mA and laser bar cavity and absorber lengths of 6 mm and 300 μm, respectively. The optimum mode-locked conditions are observed under injection current and reverse bias voltage of 124 mA and −7 V, which generates pulses at a repetition rate of 7.3 GHz, an optical bandwidth of 0.97 nm, and a nearly transform limited pulse width of 2 ps (sech2 pulse profile). These results enable QD-MLLs to be integrated with silicon photonic integrated circuits, such as optical time division multiplexing and optical clocks.

Design of uncooled high-bandwidth ultra-low energy per bit quantum dot laser transmitters for chip to chip optical interconnects

In this paper, we discuss our approach to developing uncooled, ultra low energy/bit QD MLL transmitters capable of providing high quality optical pulse trains suitable for multiplexing up to the 100 s of Gbps level. Up until now an analytical method to guide the design of temperature resistant MLLs based on convenient, measureable material parameters has not existed.

110 °C operation of monolithic quantum dot passively mode-locked lasers

Record performance over temperature is reported in a two-section InAs/GaAs quantum dot passively mode-locked laser. Stable pulses with less than 18 ps full-width-half-max are observed from 20-110 °C.