Devang Parekh

Strong optical injection-locked semiconductor lasers demonstrating >100-GHz resonance frequencies and 80-GHz intrinsic bandwidths

By using strong optical injection locking, we report resonance frequency enhancement in excess of 100 GHz in semiconductor lasers. We demonstrate this enhancement in both distributed feedback (DFB) lasers and vertical-cavity surface-emitting lasers (VCSELs), showing the broad applicability of the technique and that the coupling Q is the figure-of-merit for resonance frequency enhancement. We have also identified the key factors that cause low-frequency roll-off in injection-locked lasers. By increasing the slave lasers DC current bias, we have achieved a record intrinsic 3-dB bandwidth of 80 GHz in VCSELs.

Novel cascaded injection-locked 1.55-μm VCSELs with 66 GHz modulation bandwidth

We demonstrate a novel cascaded configuration of optically injection-locked (COIL) VCSELs, which enables a wide and tailorable direct modulation bandwidth. Up to 66 GHz bandwidth is achieved using VCSELs with an original, free-running 10 GHz bandwidth. Different configurations of cascading are discussed in detail with the focus on optimizing the modulation bandwidth. We also discuss scaling capability of this technique to achieve tailorable modulation response.

Broadband Modulation Performance of 100-GHz EO Polymer MZMs

We experimentally characterize the performance of 100-GHz electro-optical polymer Mach-Zehnder modulators in both dual-drive and single-drive versions using broadband modulation. For the dual-drive version, we measure bit-error rate (BER) at 80 Gbit/s for differential phase-shift keying (DPSK) and >; 90 Gbit/s for on-off keying (OOK). The eye diagrams of 100 Gbit/s OOK and S21 measurement of up to 110-GHz further indicate a response bandwidth of >;100 GHz. Tunable-chirp operation is also demonstrated by changing the phase and amplitude of each driving signal. For the single-drive version, a BER of 10-9 is achieved for both 100-Gbit/s OOK and DPSK signals without optical or electrical equalization. The single-drive version shows a 7-dB bandwidth of >; 110-GHz and a chirp factor of as low as -0.02.

Performance of a Multi-Gb/s 60 GHz Radio Over Fiber System Employing a Directly Modulated Optically Injection-Locked VCSEL

A multi-Gb/s 60 GHz radio over fiber (RoF) system employing direct modulation of an optically injection locked vertical-cavity surface-emitting laser is successfully demonstrated. Experimental results show that the RoF system is tolerant to fiber chromatic dispersion due to inherent single-sideband modulation produced by injection locking. A simple carrier-to-sideband equalization method is used to substantially improve the sensitivity of the RoF system by 18 dB, enabling both successful wireless signal transmission and multilevel signal modulation formats such as quadrature phase shift keying (QPSK). At least 3 Gb/s ASK-modulated data and 2 Gb/s QPSK-modulated data is transported over up to 20 km standard single-mode fiber and 3 m wireless distance with no penalty.

Optoelectronic Oscillators Using Direct-Modulated Semiconductor Lasers Under Strong Optical Injection

In this paper, optoelectronic oscillators (OEOs) are demonstrated by using direct-modulated edge-emitting lasers under strong optical injection. The optically injection-locked OEO (OIL-OEO) enables a stable optoelectronic oscillation by converting an optical signal to an electrical signal through a long optical fiber loop. Low RF threshold gain of 7 dB for loop oscillation is attained by utilizing the cavity resonance amplification of an injection-locked semiconductor laser. We investigated both the open- and closed-loop characteristics of the OIL-OEO link by varying the injection locking parameters. Using this novel technique with optimized locking parameters, a 20-GHz RF signal with a phase noise of -123 dBc/Hz is successfully achieved without sophisticated frequency or temperature stabilization.

Reconfigurable Multifunctional Operation Using Optical Injection-Locked Vertical-Cavity Surface-Emitting Lasers

In this paper, we extend the system application of optical injection-locked (OIL) vertical-cavity surface-emitting lasers (VCSELs) to future optical networks by realizing multifunctional operation using a filter-assisted OIL-VCSEL scheme that can be reconfigured. By using a single chirp-adjustable injection-locked VCSEL (either single mode or multimode) followed by a tunable delay line interferometer, we experimentally demonstrate three functions, showing ultra-wide band (UWB) monocycle generation, nonreturn-to-zero (NRZ) to pseudoreturn-to-zero (PRZ) data format conversion, and NRZ-data clock recovery at 10 Gb/s.

Nanophotonic integrated circuits from nanoresonators grown on silicon

Harnessing light with photonic circuits promises to catalyse powerful new technologies much like electronic circuits have in the past. Analogous to Moores law, complexity and functionality of photonic integrated circuits depend on device size and performance scale. Semiconductor nanostructures offer an attractive approach to miniaturize photonics. However, shrinking photonics has come at great cost to performance, and assembling such devices into functional photonic circuits has remained an unfulfilled feat. Here we demonstrate an on-chip optical link constructed from InGaAs nanoresonators grown directly on a silicon substrate. Using nanoresonators, we show a complete toolkit of circuit elements including light emitters, photodetectors and a photovoltaic power supply. Devices operate with gigahertz bandwidths while consuming subpicojoule energy per bit, vastly eclipsing performance of prior nanostructure-based optoelectronics. Additionally, electrically driven stimulated emission from an as-grown nanostructure is presented for the first time. These results reveal a roadmap towards future ultradense nanophotonic integrated circuits.

Greatly enhanced modulation response of injection-locked multimode VCSELs

We report greatly enhanced modulation response of multimode vertical-cavity surface-emitting lasers (MM-VCSELs), for the first time, using optical injection locking. A 3-dB bandwidth of 38 GHz and 54 GHz resonance frequency are achieved using a MM-VCSEL with a 3 GHz free-running bandwidth. We show that transverse mode selection can be attained with optical injection locking through frequency and spatial detuning.

Greatly increased fiber transmission distance with an optically injection-locked vertical-cavity surface-emitting laser

We demonstrate single-mode fiber transmission distance enhancement up to 120 km of a directly-modulated injection-locked VCSEL modulated by a 10Gb/s NRZ signal. Injection locking induced data pattern inversion of the VCSEL causes adjustable chirp, which greatly extends reach. Both experiments and simulations are shown to explain this phenomenon.

Long distance single-mode fiber transmission of multimode VCSELs by injection locking.

We report greatly enhanced transmission distance of multimode vertical-cavity surface-emitting lasers (MM-VCSELs) over standard single-mode fiber using optical injection locking. Transmission distance as high as 90 km is achieved at 10 Gb/s by frequency chirp inversion and higher order transverse mode suppression.