Chirp Behavior Research Articles

Frequency stability of RF-excited CO/sub 2/ waveguide lasers in gain-switched and Q-switched regimes

The behavior of an RF-excited waveguide laser is analyzed in a gain-switched and a Q-switched regime measuring the frequency sweep during the optical pulse. This enables laser-induced medium perturbations (LIMP) to be directly distinguished from the effects of the discharge power loading. The experimental observations confirm that the main perturbation in the laser output frequency is to be attributed to thermal energy variations. This gives the result of a Q-switch chirp more than one order of magnitude smaller than in the pulsed current mode, suggesting the use of Q-switching waveguide lasers in applications such as long range or Doppler laser radar systems. The chirp behavior in the pulsed current mode can show overshot relaxation corresponding to the propagation of density waves in the guide. >

Transient chirping in distributed-feedback (DFB) lasers: effect of spatial hole-burning along the laser axis

An analysis of the chirping behavior of directly modulated distributed-feedback (DFB) lasers which takes into consideration the effects of spatial hole-burning along the laser axis is discussed. Rate equations including these effects are derived. To calculate the rate equations, the threshold condition of phase-shifted DFB lasers with a nonuniform refractive index distribution is analyzed. The calculations are carried out on phase-shifted DFB structures under the condition of random nonreturn to zero modulation at 1.8 Gb/s. The results show that the spatial hole-burning along the axis significantly affects the chirping behavior, adding to the effects induced by the spectral hole-burning alone.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Chirp behaviour of high-speed GaInAsP/InP optical intensity modulator

A low chirp characteristic was observed in a high-speed GaInAsP/InP BH optical intensity modulator with a bandwidth of 14 GHz. The maximum chirp was about 0.8 Å under large-signal pulse modulation. This value agrees well with the calculated result using the αE parameter which was directly evaluated by a change in the complex refractive index.

Chirp in picosecond pulses from diode lasers: Dependence on the modulation conditions and linewidth enhancement factor

This paper reports on the first experimental study in the large-signal domain on the relation between the linewidth enhancement factor α and the frequency chirp of picosecond pulses from diode lasers. The time-bandwidth product is found to be constant over a wide range of operating conditions, in good agreement with theory. Different laser structures in the same material (GaAs) are shown to have significantly different chirp behavior and α parameters, thereby experimentally verifying the structural dependence of the α parameter. Simulations based on the standard rate-equations are also performed, and it is found that considerable chirp can be present even in pulses having time-bandwidth products less than one.

Sensory feedback from electroreceptors to electromotor pacemaker centers in gymnotids

Sensory feedback from electroreceptors to electromotor pacemaker centers in gymnotids