1,521 research outputs found
Unnested islands of period-doublings in an injected semiconductor laser
We present a theoretical study of unnested period-doubling islands in three-dimensional rate equations modeling a semiconductor laser subject to external optical injection. In this phenomenon successive curves of period doublings are not arranged in nicely nested islands, but intersect each other. This overall structure is globally organized by several codimension-2 bifurcations. As a consequence, the chaotic region existing inside an unnested island of period doublings can be entered not only via a period-doubling cascade but also via the breakup of a torus, and even via the sudden appearance of a chaotic attractor. In order to fully understand these different chaotic transitions we reveal underlying global bifurcations and we show how they are connected to codimension-2 bifurcation points. Unnested islands of period doublings appear to be generic and hence must be expected in a large class of dynamical systems
Compound laser modes of mutually delay-coupled lasers : bifurcation analysis of the locking region
Bifurcation analysis of a semiconductor laser with filtered optical feedback
We study the dynamics and bifurcations of a semiconductor laser with delayed filtered optical feedback, where a part of the output of the laser reenters after spectral filtering. This type of coherent optical feedback is more challenging than the case of conventional optical feedback from a simple mirror, but it provides additional control over the output of the semiconductor laser by means of choosing the filter detuning and the filter width. This laser system can be modeled by a system of delay differential equations with a single fixed delay, which is due to the travel time of the light outside the laser. In this paper we present a bifurcation analysis of the filtered feedback laser. We first consider the basic continuous wave states, known as the external filtered modes (EFMs), and determine their stability regions in the parameter plane of feedback strength versus feedback phase. The EFMs are born in saddle-node bifurcations and become unstable in Hopf bifurcations. We show that for small filter detuning there is a single region of stable EFMs, which splits up into two separate regions when the filter is detuned. We then concentrate on the periodic orbits that emanate from Hopf bifurcations. Depending on the feedback strength and the feedback phase, two types of oscillations can be found. First, there are undamped relaxation oscillations, which are typical for semiconductor laser systems. Second, there are oscillations with a period related to the delay time, which have the remarkable property that the laser frequency oscillates while the laser intensity is almost constant. These frequency oscillations are only possible due to the interaction of the laser with the filter. We determine the stability regions in the parameter plane of feedback strength versus feedback phase of the different types of oscillations. In particular, we find that stable frequency oscillations are dominant for nonzero values of the filter detuning. © 2007 Society for Industrial and Applied Mathematics
Giant phase-conjugate reflection with a normal mirror in front of an optical phase-conjugator
We theoretically study reflection of light by a phase-conjugating mirror
preceded by a partially reflecting normal mirror. The presence of a suitably
chosen normal mirror in front of the phase conjugator is found to greatly
enhance the total phase-conjugate reflected power, even up to an order of
magnitude. Required conditions are that the phase-conjugating mirror itself
amplifies upon reflection and that constructive interference of light in the
region between the mirrors takes place. We show that the phase-conjugate
reflected power then exhibits a maximum as a function of the transmittance of
the normal mirror.Comment: 8 pages, 3 figures, RevTe
Pure frequency oscillations of semiconductor lasers with filtered optical feedback
A semiconductor laser subject to delayed filtered optical feedback can show pure frequency
oscillations with a period of the order to the delay time, while the power remains practically constant. This is remarkable in light of the strong self-phase modulation in semiconductor lasers that couples frequency and power. It turns out that the dynamics of the filter plays an essential role in this behavior, because it changes the instantaneous amount of feedback in response to the instantaneous laser frequency. By using numerical bifurcation techniques we show how frequency oscillations bifurcate in Hopf bifurcatious from the continuous wave solutions known as external filtered modes
Bound Modes in Dielectric Microcavities
We demonstrate how exactly bound cavity modes can be realized in dielectric
structures other than 3d photonic crystals. For a microcavity consisting of
crossed anisotropic layers, we derive the cavity resonance frequencies, and
spontaneous emission rates. For a dielectric structure with dissipative loss
and central layer with gain, the beta factor of direct spontaneous emission
into a cavity mode and the laser threshold is calculated.Comment: 5 pages, 3 figure
Relaxation oscillation dynamics in semiconductor diode lasers with optical feedback
We theoretically investigate the stability of a single-mode semiconductor laser with weak optical feedback in the short external-delay regime. Although the laser is, in general, very sensitive to feedback-induced excitation of relaxation oscillations, we predict complete insensitivity for these oscillations when the product of oscillation frequency and external-delay time equals a small integer. This may form the basis for relaxation-oscillation-free laser design
Frequency versus relaxation oscillations in a semiconductor laser with coherent filtered optical feedback
We investigate the dynamics of a semiconductor laser subject to coherent delayed filtered optical feedback. A systematic bifurcation analysis reveals that this system supports two fundamentally different types of oscillations, namely relaxation oscillations and external roundtrip oscillations. Both occur stably in large domains under variation of the feedback conditions, where the feedback phase is identified as a key quantity for controlling this dynamical complexity. We identify two separate parameter regions of stable roundtrip oscillations, which occur throughout in the form of pure frequency oscillations
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