816 research outputs found
Transient Cherenkov radiation from an inhomogeneous string excited by an ultrashort laser pulse at superluminal velocity
An optical response of one-dimensional string made of dipoles with a
periodically varying density excited by a spot of light moving along the string
at the superluminal (sub-luminal) velocity is theoretically studied. The
Cherenkov radiation in such system is rather unusual, possessing both transient
and resonant character. We show that under certain conditions, in addition to
the resonant Cherenkov peak another Doppler-like frequency appears in the
radiation spectrum. Both linear (small-signal) and nonlinear regimes as well as
different string topologies are considered.Comment: accepted to Phys. Rev.
Generation of unipolar half-cycle pulse via unusual reflection of a single-cycle pulse from an optically thin metallic or dielectric layer
We present a significantly different reflection process from an optically
thin flat metallic or dielectric layer and propose a strikingly simple method
to form approximately unipolar half-cycle optical pulses via reflection of a
single-cycle optical pulse. Unipolar pulses in reflection arise due to
specifics of effectively one-dimensional pulse propagation. Namely, we show
that in considered system the field emitted by a flat medium layer is
proportional to the velocity of oscillating medium charges instead of their
acceleration as it is usually the case. When the single-cycle pulse interacts
with linear optical medium, the oscillation velocity of medium charges can be
then forced to keep constant sign throughout the pulse duration. Our results
essentially differ from the direct mirror reflection and suggest a possibility
of unusual transformations of the few-cycle light pulses in linear optical
systems
Self-starting stable coherent mode-locking in a two-section laser
Coherent mode-locking (CML) uses self-induced transparency (SIT) soliton
formation to achieve, in contrast to conventional schemes based on absorption
saturation, the pulse durations below the limit allowed by the gain line width.
Despite of the great promise it is difficult to realize it experimentally
because a complicated setup is required. In all previous theoretical
considerations CML is believed to be non-self-starting. In this article we show
that if the cavity length is selected properly, a very stable (CML) regime can
be realized in an elementary two-section ring-cavity geometry, and this regime
is self-developing from the non-lasing state. The stability of the pulsed
regime is the result of a dynamical stabilization mechanism arising due to
finite-cavity-size effects
Recommended from our members
Self-starting stable coherent mode-locking in a two-section laser
In the present work we report the possibility of passive mode-locking based on the coherent interaction of light with the amplifying and absorbing media in lasers with ring and linear cavities. We consider the realistic and practically interesting case when the absorbing and amplifying media are separated in the cavity space but not homogeneously mixed in the volume of the cavity, as was considered earlier in the literature. We perform qualitative consideration of coherent passive mode-locking based on the area theorem of McCall and Hahn and its graphical representation for the first time. We show that other, not soliton scenarios of passive mode-locking exist, and that coherent mode-locking is self-starting (lasing without an injection seeding pulse is possible). We point to the fact that the spectral width of the laser generation can be significantly larger than the spectral bandwidth of the gain medium. Numerical simulations were performed using the system of Maxwell-Bloch equations in the slowly varying envelope approximation
Coherent passive mode-locking in lasers: Qualitative analysis and numerical simulations
In the present work we report the possibility of passive mode-locking based on the coherent interaction of light with the amplifying and absorbing media in lasers with ring and linear cavities. We consider the realistic and practically interesting case when the absorbing and amplifying media are separated in the cavity space but not homogeneously mixed in the volume of the cavity, as was considered earlier in the literature. We perform qualitative consideration of coherent passive mode-locking based on the area theorem of McCall and Hahn and its graphical representation for the first time. We show that other, not soliton scenarios of passive mode-locking exist, and that coherent mode-locking is self-starting (lasing without an injection seeding pulse is possible). We point to the fact that the spectral width of the laser generation can be significantly larger than the spectral bandwidth of the gain medium. Numerical simulations were performed using the system of Maxwell-Bloch equations in the slowly varying envelope approximation
Stabilization of class-B broad-area lasers emission by external optical injection
We theoretically examine the effect of external optical injection on the
spatio-temporal dynamics of class-B broad-area lasers. We demonstrate that
optical injection can efficiently stabilize the intrinsic transverse
instabilities in such lasers associated with both the boundaries of the pumping
area and with the bulk nonlinearities of the active medium. Stabilizing action
of optical injection is shown to be closely related to the suppression of
inherent relaxation oscillations behavior.Comment: 8 pages, 7 figure
- …