Pietro R. A. Binetti

Two-Dimensional Optical Beam Steering With InP-Based Photonic Integrated Circuits

Two-dimensional optical beam steering using an InP photonic integrated circuit has been demonstrated. Lateral beam steering controlled by a 1-D phased array has been made easier through on-chip interferometer monitors. Longitudinal beam steering controlled by the input wavelength has demonstrated an efficiency of 0.14 °/nm. Very fast beam steering (>107 °/s) in both dimensions has been demonstrated as well. As the latest development, a widely tunable sampled-grating distributed Bragg reflector laser has been monolithically integrated and 2-D beam steering has been demonstrated with this on-chip tunable laser source.

Monolithically Integrated Gain-Flattened Ring Mode-Locked Laser for Comb-Line Generation

We demonstrate broadband comb-line generation from an integrated multiple quantum well InGaAsP/InP passively mode-locked laser (MLL) with a gain flattening filter (GFF) based on an asymmetric Mach-Zehnder interferometer. The intracavity filter flattens the nonuniform gain profile of the semiconductor material providing a more uniform net cavity gain. The GFF MLL has a -10 dB comb span of 15 nm (1.88 THz), the widest spectral width yet demonstrated for an integrated QW MLL at 1.55 μm . The measured optical linewidth at the center of the comb is 29 MHz, the -20 dB RF linewidth 500 KHz, while the output spectrum is phase-locked to produce 900 fs pulses at a repetition rate of 30 GHz with 4.6 ps integrated jitter from 100 Hz to 30 MHz.

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.

Theory and Design of THz Intracavity Gain-Flattened Filters for Monolithically Integrated Mode-Locked Lasers

We present the theory and design of a tunable gain-flattening filter for integrated mode-locked lasers (MLLs). The filter provides the inverse of the semiconductor spectral gain profile and produces a broad flattened net gain. This improves the performance of MLLs by allowing more modes to lase simultaneously. We demonstrate a gain-flattened MLL with a record 10 dB bandwidth of 2.08 THz, the widest frequency comb span for an integrated quantum-well-based laser at 1.55 μm. Gain-flattening theory is used to extend the integrated comb span to 40 nm. We use scattering matrices to investigate feed-forward filters based on asymmetric Mach-Zehnder interferometers (MZIs). We compare MZI filters designed for a fixed coupling value to those that use an active gain arm to adjust the extinction ratio. Tunable zero placement of these filters is achieved using a passive phase tuning arm. The optimized gain-flattening filter has a 5 dB extinction ratio and a 70 nm free-spectral-range. When the filter is incorporated into a ring MLL, simulations predict a 40 nm, i.e., 5 THz, comb span with a power variation <; 3.5 dB.

InP photonic integrated circuit for 2D optical beam steering

InP photonic integrated circuit for 2D (5°×10°) optical beam steering has been demonstrated for the first time. Design, fabrication, and preliminary results are presented.

Integrated 30GHz passive ring mode-locked laser with gain flattening filter

We demonstrated a 30GHz integrated InGaAsP/InP ring mode-locked laser with a gain flattening filter that doubles the locking bandwidth and decreases the pulse width from 840fs to 620fs.

Frequency Tuning in Integrated InGaAsP/InP Ring Mode-Locked Lasers

We demonstrate for the first time, continuous frequency tuning >;40 MHz using symmetric phase tuning regions in an InGaAsP/InP 18 GHz passively mode-locked ring laser. Frequency tuning is achieved through current injection into passive waveguides, via the free-carrier plasma effect, which is enhanced by the concurrent increase in cavity losses from free-carrier absorption. Stable mode-locking with ~1 ps pulse-width is realized from -2.5 to -7.5 V bias on the saturable absorber and 170 to 290 mA drive current. The average RF power is 50 dB above the noise level over this regime.

Improved performance of optical beam steering through an InP photonic integrated circuit

Optical beam steering through an InP photonic integrated circuit has been improved in term of side-lobe suppression (13dB from -14° to 14° around the peak) and steering angle (10° by 28nm wavelength tuning).

InP photonic integrated circuit with on-chip monitors for optical beam steering

Optical beam steering controlled by an array of phase shifters from an InP photonic integrated circuit has been demonstrated with the help from on-chip monitors.

RIE lag directional coupler based integrated InGaAsP/InP ring mode-locked laser

We have demonstrated the first integrated ring mode-locked laser (MLL) with a reactive ion etch (RIE) lag coupler. The RIE lag directional coupler (RL-DC) is highly advantageous for integrated MLLs as it has an insertion loss &#60;1 dB and can be designed to provide any coupling value. This provides the RL-DC with a much needed flexibility in large photonic systems unlike standard multimode interference (MMI) couplers, which typically provide only 3 dB power splitting.