Generation of dark solitons under a cw background using waveguide electro-optic modulators.

We propose a novel method for generating dark solitons with a cw background by using broadband guided-wave electro-optic modulators. The generated pulse can be amplified by stimulated Raman scattering to permit the observation of soliton effects in the fiber.

Propagation properties of dark solitons.

We numerically study the initial-value problem of the nonlinear Schrödinger equation in the normal-dispersion regime of an optical fiber. A nonchirped hyperbolic tangent input pulse having arbitrary amplitude is found to evolve into a primary dark soliton having a constant amplitude and speed. The effect of the input amplitude is to alter the pulse width of the primary dark soliton. In addition, a set of secondary dark solitons of smaller amplitude moving away from the primary pulse is also generated. It is also shown that nonlinear dark pulses in optical fibers are more stable than bright pulses with respect to loss and noise.

Periodic amplification of dark solitons using stimulated Raman scattering.

The possibility of periodically amplifying dark solitons in a normally dispersive optical fiber is studied. It is found that, as with bright solitons, an all-optical, repeaterless, and stable system for dark-soliton transmission at a rate of 20 GHz over thousands of kilometers in a lossy fiber is achievable, if periodic amplification using stimulated Raman scattering is incorporated.

Interactions between dark solitons.

The interaction forces between two dark solitons are numerically investigated. It is found that dark solitons are less affected than bright solitons by their respective interaction forces. An empirical expression for the separation of two solitons as a function of initial separation and traveling distance is deduced, which agrees well with numerical results.

Passive mode locking of the Ar(+) laser.

We have studied passive mode locking of the Ar(+) laser using the saturable absorber rhodamine 6G in four different regimes as follows: when the Ar(+) laser operates in the colliding pulse mode locking configuration (1) with and (2) without double mode locking incorporated and also when the Ar(+) laser operates in the conventional configuration (3) with and (4) without double mode locking incorporated. A detailed investigation of the Ar(+) and dye laser pulses from the double mode-locked Ar(+)-dye laser system is made using correlation measurements. A direct display of a 67-ps Ar(+) pulse shape is measured. Parametric studies provide insight into the fundamental mechanisms involved in the production of the pulses, and also show that the colliding pulse regime, where two Ar(+) pulses interact coherently in the saturable absorber, is favorable as far as stability and minimum pulse durations are concerned for this system.

Evolution of femtosecond pulses in single-mode fibers having higher-order nonlinearity and dispersion.

Using computer simulations, we examine the effects of higher-order dispersive and nonlinear propagation processes on the spectral and time development of ultrashort, high-intensity pulses propagating in single-mode optical fibers having normal dispersion. Our results indicate that both the cubic-dispersion term and the shock term of the nonlinear Schrödinger equation contribute to asymmetry in the pulse power spectrum and cause highly nonlinear chirp.

Independent tunability of the double-mode-locked cw dye laser.

We report a new configuration that enables the double-mode-locked cw dye laser to be independently tunable. In addition, the output coupling at each of the two wavelengths can be independently specified. A series of oscillographs shows some interesting features unique to double mode locking and also shows the effects of varying the two cavity lengths with respect to each other.