Abirami Sivananthan

Highly integrated optical heterodyne phase-locked loop with phase/frequency detection.

A highly-integrated optical phase-locked loop with a phase/frequency detector and a single-sideband mixer (SSBM) has been proposed and demonstrated for the first time. A photonic integrated circuit (PIC) has been designed, fabricated and tested, together with an electronic IC (EIC). The PIC integrates a widely-tunable sampled-grating distributed-Bragg-reflector laser, an optical 90 degree hybrid and four high-speed photodetectors on the InGaAsP/InP platform. The EIC adds a single-sideband mixer, and a digital phase/frequency detector, to provide single-sideband heterodyne locking from -9 GHz to 7.5 GHz. The loop bandwith is 400 MHz.

Monolithic Integration of a High-Speed Widely Tunable Optical Coherent Receiver

In this letter, a monolithically integrated widely tunable optical receiver is demonstrated. A sampled-grating DBR (SG-DBR) laser, an optical 90-degree hybrid, four high-speed uni-travelling-carrier photodetectors and microstrip transmission lines are integrated on a single InGaAsP/InP chip. A 42-nm tuning range and a 35-GHz detector bandwidth are achieved. Experiments show real-time reception of 40 Gb/s BPSK data.

An Integrated 40 Gbit/s Optical Costas Receiver

In this paper, a highly-integrated widely-tunable optical homodyne receiver is reported with 40 Gbaud/s data rate. By using photonic and electronic integration, the receiver is realized within a size of 10 × 10 mm2, and the system is very robust and resistive to environmental changes. An integrated photonic coherent receiver circuit is demonstrated with 35 GHz photodetector bandwidth, and the integrated local oscillator (LO) laser covers a 40 nm range. The electronic IC (EIC) has a working frequency up to 50 GHz. The feedback loop is carefully analyzed and designed, and the experimental results show > 1.1 GHz loop bandwidth, which matches the design. The hold-in range is measured to be > 15 GHz. The phase noise of the transmitting laser has been cloned to the LO laser quite well, and both the linewidth measurement and phase noise measurement show no observable cross talk between binary phase shift keying (BPSK) data and the optical phase-locked loop (OPLL). Error free ( bit error rate <; 10-12) is achieved up to 35 Gbit/s. The system consumes 3 Watts of power.

Indium Phosphide Photonic Integrated Circuits for Coherent Optical Links

We demonstrate photonic circuits monolithically integrated on an InP-based platform for use in coherent communication links. We describe a technology platform that allows for the integration of numerous circuit elements. We show examples of an integrated transmitter which offers an on-chip wavelength-division-multiplexing source with a flat gain profile across a 2 THz band and a new device design to provide a flatted gain over a 5 THz band. We show coherent receivers incorporating an integrated widely tunable local oscillator as well as an optical PLL. Finally, we demonstrate a tunable optical bandpass filter for use in analog coherent radio frequency links with a measured spurious-free dynamic range of 86.3 dB-Hz2/3 as well as an improved design to exceed 117 dB-Hz2/3.

Highly-Stable Integrated InGaAsP/InP Mode-Locked Laser and Optical Phase-Locked Loop

We demonstrate an integrated InGaAsP/InP mode-locked laser that is stabilized with an optical phase-locked loop (OPLL). Using the OPLL, a single comb line is locked to a reference oscillator (a 200 Hz linewidth Brillouin laser). The comb linewidth is reduced from 100 MHz (unlocked) to <; 550 Hz (locked) using the OPLL. The rms phase error between the comb and reference laser is 20°. The linewidth of the adjacent comb lines is <; 1 kHz, and the comb spans 430 GHz.

A heterodyne optical phase-locked loop for multiple applications

A novel heterodyne optical phase-locked loop (OPLL) has been achieved and testing results are demonstrated with a 0.03 rad2 phase error variance. Based on the superior performance of this OPLL, a system prototype is shown for multiple applications, including free-space LIDAR systems, widely-and-fast-tunable ultra-narrow-linewidth lasers, and ultra-accurate optical spectrum analyzers.

Formation of sub-10 nm width InGaAs finFETs of 200 nm height by atomic layer epitaxy

As FETs are scaled, the dielectric and semiconductor channel thicknesses must be reduced to suppress short-channel effects. Even using fin field effect transistors (finFETs) and gate all around FETs (GAAFETs), [1],[2], whose electrostatic performance is excellent, at 4nm gate length the channel should be less than 2nm thick. To obtain high drive current per unit IC die area, the fin height should be many times the fin pitch, i.e. tens to hundreds of nm. Dry-etching a fin of few-nm width and > 100 nm height presents severe challenges in control of etch sidewall slope and in minimizing surface damage. Here we report an InGaAs finFET fabrication flow which form fins of sub-10nm width and 200 nm height. Fin width is controlled by atomic layer epitaxial (ALE) growth and by semiconductor selective crystallographic wet etching. We further demonstrate self-aligned source-drain regrowth in this process [3],[4]. This facilitates scaling of the source/drain pitch to small dimensions.

A widely-tunable integrated coherent optical receiver using a phase-locked loop

A novel widely-tunable coherent receiver incorporating an optical phased-locked loop (OPLL) on two adjacent chips-a photonic IC and an electronic IC-is described. The design of both is novel, but the focus will be on the photonic IC in this paper. Results indicate a high degree of functionality.

Integrated phase-locked multi-THz comb for broadband offset locking

We demonstrate an integrated InGaAsP/InP 2.06 THz broadband comb for offset locking SG-DBR widely tunable lasers. The comb has 70 lasing lines and is generated using a hybrid mode-locked laser with intracavity gain flattening.

Optical Phase-Locking and Wavelength Synthesis

We describe techniques for phase-locked coherent optical communications, including wavelength synthesis for wavelength-division-multiplexed optical communications, compact coherent BPSK receivers, and coherent demodulation of WDM in the electrical domain. Index Terms - Coherent optical communications, phase-locked-loops, frequency synthesis, wavelength-division-multiplexing.