High On-off Contrast Ratio Research Articles

Two-Wavelength Switching With a 1310-nm Quantum Dot Distributed Feedback Laser

Two-wavelength switching operation and bistability is reported for the first time with a 1310-nm quantum-dot (QD) distributed feedback (DFB) laser. We demonstrate experimentally the switching of the lasing mode of the QD laser under external optical injection into one of the residual Fabry-Perot (FP) modes of the device. Clockwise switching and bistability occurs for both the lasing and the injected subsidiary modes of the QD DFB laser as the injection strength is increased. Moreover, very high ON-OFF contrast ratio is measured for the switching transition of the lasing mode of the device. We have also analyzed experimentally the influence of two important system parameters, namely the initial wavelength detuning and the applied bias current. The variety of switching behaviors obtained with a 1310-nm QD DFB laser added to the theoretically superior properties of nanostructure lasers offers exciting prospects for novel uses of these devices in all-optical logic and all-optical switching/routing applications in present and future optical telecommunication networks.

Bistability patterns and nonlinear switching with very high contrast ratio in a 1550 nm quantum dash semiconductor laser

We report on the experimental observation of optical bistability (OB) and nonlinear switching (NS) in a nanostructure laser; specifically a 1550 nm quantum dash Fabry-Perot laser subject to external optical injection and operated in reflection. Different shapes of optical bistability and nonlinear switching, anticlockwise and clockwise, with very high on-off contrast ratio (up to 180:1) between output states were experimentally measured. These results added to the potential of nanostructure lasers for enhanced performance offer promise for use in fast all-optical signal processing applications in optical networks.

Two-Wavelength Switching With a 1550 nm VCSEL Under Single Orthogonal Optical Injection

We report the first experimental observation of three distinct forms of two-wavelength switching (clockwise, anticlockwise, and butterfly) for a 1550 nm vertical cavity surface emitting laser (VCSEL) operated just above threshold and subject to orthogonally polarized optical injection. The spectrum of the device exhibits two modes, a main mode emitting in a "parallel'' polarization and a subsidiary "`orthogonal'' polarized mode. Low input-power switching of the emission wavelength of the VCSEL by an orthogonally polarized external optical signal injected to the long-wavelength side of the subsidiary mode is observed. Clockwise switching and bistability of the main lasing mode with very high on-off contrast ratio has been measured in all cases. Three different switching shapes: anticlockwise, butterfly, and clockwise, have been measured for the output of the optically injected VCSEL. This diversity of switching behavior with a 1550 nm VCSEL subject to optical injection offers promise for the use of these devices in all-optical switching/routing as well as optical interconnect applications.

Bistability and nonlinear gain in 1.55μm vertical cavity semiconductor optical amplifiers: Theory and experiments

We report experimental measurements of power and wavelength optical bistability and nonlinear gain in two 1.55μm vertical-cavity semiconductor optical amplifiers operated in reflection. Anticlockwise and clockwise nonlinear switching and bistability, both with high on-off contrast ratio up to 3.5:1, have been observed in the optical power and wavelength domains. Theoretical modeling gives excellent agreement with the experimental measurements.

All-optical flip-flop with high on-off contrast ratio using two injection-locked single-mode Fabry-Perot laser diodes

An all-optical flip-flop with inverted output is presented. The flip-flop is realized based on the optical bistability of an injection-locked single-mode Fabry-Perot laser diode (FP-LD). The operation principle is explained and experimental results are presented in this paper. The flip-flop with separate optical set and reset inputs had an on-off contrast ratio of over 35 dB.

Femtosecond all-optical wavelength and time demultiplexer for OTDM/WDM systems

In this contribution we present a proof of concept for a femtosecond all-optical demultiplexer based on the diffraction of a pulsed laser beam by an ultrafast transient refractive index grating formed in barium fluoride. The instantaneous character of the grating is demonstrated by measuring the temporal response of the first diffracted order of an independent laser beam. We achieve an overall switching efficiency of >23% (>18% for m=1), with an extremely high on-off contrast ratio. Our arrangement provides wavelength-dependent diffraction and shows its potential as a demultiplexer for wavelength division multiplexing.

All-Fiber Optical Signal Inversion Using Stimulated Raman Scattering

We propose a method for all-optical signal inversion by means of stimulated Raman scattering (SRS). The idea is based on the transference of energy from the logic state #x201C;1#x201D; to the second stokes and making the logic state #x201C;0#x201D; into logic state #x201C;1#x201D; by receiving energy from the pump through SRS. According to the numerical simulation, a continuous wave pump source of LOW at 1453 nm and a few hundred meters of highly nonlinear fiber are required to invert an input signal at 1555 nm. The optical signal is inverted with high on-off contrast ratio.

Design and simulation of a broadband, high speed quasioptical beam switch array for moderate pulse reflectometry

High speed, high on-off contrast ratio switches utilizing beam control grid array technology are under development for use in moderate pulse reflectometry. This approach, which utilizes arrays consisting of hundreds of Shottky varactor diodes embedded within an overmoded wave guide, is expected to generate switching times in the 100–500 ps range with high power handling capabilities. The switches are designed for initial wideband operation in V band (50–75 GHz) operation although they can be operated both at lower and higher frequencies, and are intended for use in a moderate pulse reflectometry system such as used on the RTP tokamak.

Improved performances of a S-SEED using extremely shallow quantum-wells and asymmetric Fabry-Perot cavity structure

The authors report significantly improved performances of a symmetric self-electrooptic-effect device (S-SEED), with high on-off contrast ratio (>30:l) and large optical bistability loop widths ( Delta P=44%) at an applied bias of V/sub a/=0 V, i.e., with no power supply. The S-SEED is made of extremely shallow quantum wells (ESQWs) in an asymmetric Fabry-Perot (AFP) cavity structure. At V/sub a/=5 V Delta P increased by up to 95%, preserving the high contrast ratio. The reflectivity changes at V/sub a/=0 and 5 V were about 15% and 30%, respectively. These are believed to be the largest values ever reported for such structures. >