14 research outputs found
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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
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Transient radiation from a circular string of dipoles excited at superluminal velocity
This paper discusses the features of transient radiation from periodic
one-dimensional resonant medium excited by ultrashort pulse. The case of
circular geometry is considered for the harmonic distribution of the density
of the particles along the circle. It is shown that a new frequency component
arises in the spectrum of the scattered radiation in addition to the
resonance frequency of medium. The new frequency appears both in the case of
linear and nonlinear interaction, its value depends on the velocity of
excitation pulse propagation and on the period of spatial modulation. In
addition, the case when excitation moves at superluminal velocity and
Cherenkov radiation arises is also studied
Transient radiation from a circular string of dipoles excited at superluminal velocity
This paper discusses the features of transient radiation from periodic one-dimensional resonant medium excited by ultrashort pulse. The case of circular geometry is considered for the harmonic distribution of the density of the particles along the circle. It is shown that a new frequency component arises in the spectrum of the scattered radiation in addition to the resonance frequency of medium. The new frequency appears both in the case of linear and nonlinear interaction, its value depends on the velocity of excitation pulse propagation and on the period of spatial modulation. In addition, the case when excitation moves at superluminal velocity and Cherenkov radiation arises is also studied
Pulse repetition-frequency multiplication in a passively mode-locked semiconductor laser coupled to an external passive cavity
Using a delay differential equation model with two time delays, we
investigate the dynamics of a semiconductor laser with an active cavity
coupled to an external passive cavity. Our numerical simulations indicate
that when the coupling between the two cavities is strong enough and the
round-trip time of the active cavity is an integer multiple of the round-trip
time of the external passive cavity, a harmonic mode-locking regime can
develop in the laser with the pulse repetition period close to the passive
cavity round trip time. We also demonstrate that the output field intensity
sensitively depends on the relative phase between the electric fields in the
two cavities giving rise to a resonant behavior. The period and width of the
resonances depend on the ratio of the round-trip times and the coupling
between the two cavities. We show that the coupled cavity system under
consideration can demonstrate a bistability between different regimes of
generation
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Semiconductor mode-locked lasers with coherent dual mode optical injection: Simulations, analysis and experiment
Using a delay differential equations model we study the dynamics of a
passively modelocked semiconductor laser with dual frequency coherent optical
injection. The locking regions where the laser pulse repetition rate is
synchronized to the separation of the two injected frequencies were
calculated numerically and measured experimentally. Asymptotic analysis
performed in the limit of the small injection field amplitude revealed the
dependence of the locking regions on the model parameters, such as optical
bandwidth, absorber recovery time and linear losses
The new ultra high-speed all-optical coherent streak-camera
In the present paper a new type of ultra high-speed all-optical coherent streak-camera
was developed. It was shown that a thin resonant film (quantum dots or molecules) could radiate
the angular sequence of delayed ultra-short pulses if a transverse spatial periodic distribution of
the laser pump field amplitude has a triangle shape
Semiconductor mode-locked lasers with coherent dual mode optical injection: Simulations, analysis and experiment
Using a delay differential equations model we study the dynamics of a passively mode-locked semiconductor laser with dual frequency coherent optical injection. The locking regions where the laser pulse repetition rate is synchronized to the separation of the two injected frequencies were calculated numerically and measured experimentally. Asymptotic analysis performed in the limit of the small injection field amplitude revealed the dependence of the locking regions on the model parameters, such as optical bandwith, absorber recovery time and linear losses
Hybrid mode-locking in edge-emitting semiconductor lasers: Simulations, analysis and experiments
Hybrid mode-locking in a two section edge-emitting semiconductor laser is studied numerically and analytically using a set of three delay differential equations. In this set the external RF signal applied to the saturable absorber section is modeled by modulation of the carrier relaxation rate in this section. Estimation of the locking range where the pulse repetition frequency is synchronized with the frequency of the external modulation is performed numerically and the effect of the modulation shape and amplitude on this range is investigated. Asymptotic analysis of the dependence of the locking range width on the laser parameters is carried out in the limit of small signal modulation. Our numerical simulations indicate that hybrid mode-locking can be also achieved in the cases when the frequency of the external modulation is approximately twice larger and twice smaller than the pulse repetition frequency of the free running passively mode-locked laser fP . Finally, we provide an experimental demonstration of hybrid mode-locking in a 20 GHz quantum-dot laser with the modulation frequency of the reverse bias applied to the absorber section close to fP =2
Transient radiation from a ring resonant medium excited by an ultrashort superluminal pulse
This paper discusses the features of transient radiation from periodic one-dimensional resonant medium excited by ultrashort pulse. The case of circular geometry is considered for the harmonic distribution of the density of the particles along the circle. It is shown that a new frequency component arises in the spectrum of the scattered radiation in addition to the resonance frequency of medium. The new frequency appears both in the case of linear and nonlinear interaction, its value depends on the velocity of excitation pulse propagation and on the period of spatial modulation. In addition, the case when excitation moves at superluminal velocity and Cherenkov radiation arises is also studied