Oscillations, Waves, and Interactions - GWDG

414 U. Parlitz
GN
differential optical gain
α 5.0 linewidth enhancement factor
γ 0.909 ns −1
carrier loss rate
Γ 0.357 ps −1
photon loss rate
Jth 1.552 · 10 8 ns −1
threshold current density
p 1.02 pump current density over Jth
2πc/ω0 635 nm solitary laser wavelength
Nsol 1.707 · 10 8
solitary laser carrier number
κ 10 11 s −1
feedback rate
τ 10 ns external cavitiy round trip time
2.142 · 10 −5 ns −1
Table 1. Typical parameter values of the Lang-Kobayashi equations (8).
et al. [15] showed that characteristics and statistics of the LFFs is indeed influenced by
this noise. Mørk et al. [16] assumed the laser to become bistable due to the feedback,
such that the spontanous emission noise would cause a mode hopping between these
two states. In 1994, Sano [17] showed that the LFF dynamics could be simulated
by the deterministic LKEs (8). Those simulations also revealed the frequency of
the fast oscillations mentioned above that were eventually visualised experimentally
by Fischer et al. [18] in 1996. In 1998 Ahlers et al. [19] showed at the DPI that
chaotic LFF dynamics generated by the LKEs may possess many positive Lyapunov
exponents (hyperchaos) and can be synchronised by optical coupling (see Sect. 5.3).
On the other hand, the chaotic fluctuations disappear if additional external cavities
are used with suitably chosen lengths and resulting delay times.
LFFs were generally assumed to be a phenomenon of only low pump currents, until
in 1997 Pan et al. [20] were the first to show both experimentally and numerically
that in case of larger feedback rates they occur for currents well above the laser
threshold as well. In this regime, power drop-outs turn into power jump-ups. They
appear like inverted power drop-outs, but their modelling is more complicated [21].
and requires multiple reflections to be taken into account [22].
Figure 7. Low frequency
fluctuations of a semiconductor
laser with weak
external optical feedback.
Simulation with the Lang-
Kobayashi equations (8)
and the parameters given
in Table 1 [19].
(a)
(b)