Recently the shortest pulses directly out of a Ti:sapphire laser as short as 6.5fs has been generated by use of single quantum well (SQW) GaAs absorber [1]. Since this laser produces pulses with durations shorter than or comparable to the polarization dephasing time and sufficient power for Rabi flopping of the excited carrier density, the noninstantaneous response of the absorber polarization has to be taken into account. We develope the theory of coherent absorber mode locking taking into account also inhomogeneous broadening of the semiconductor transition by freely movable carriers and Coulomb renormalization of the transition frequency in the scope of semiconductor Bloch equations. Photo-echo measurements in highly excited GaAs yield a decreasing of the effective dephasing with increasing of the laser excited carrier density as T2 ∝ N-1/3. In the SQW absorber the center wavelength of 750nm is well above the bandedge of the GaAs SQW at 870nm and the broad pulse spectrum excites mainly 3D carriers above the confinement depth. We have shown that Rabi-flopping is self-consistently produced due to sub10fs pulse formation at TW/cm2 intensities corresponding to an excited carrier density up to 1020cm-3.Recently the shortest pulses directly out of a Ti:sapphire laser as short as 6.5fs has been generated by use of single quantum well (SQW) GaAs absorber [1]. Since this laser produces pulses with durations shorter than or comparable to the polarization dephasing time and sufficient power for Rabi flopping of the excited carrier density, the noninstantaneous response of the absorber polarization has to be taken into account. We develope the theory of coherent absorber mode locking taking into account also inhomogeneous broadening of the semiconductor transition by freely movable carriers and Coulomb renormalization of the transition frequency in the scope of semiconductor Bloch equations. Photo-echo measurements in highly excited GaAs yield a decreasing of the effective dephasing with increasing of the laser excited carrier density as T2 ∝ N-1/3. In the SQW absorber the center wavelength of 750nm is well above the bandedge of the GaAs SQW at 870nm and the broad pulse spectrum excites mainly 3D carriers above the confinement depth. We have shown that Rabi-flopping is self-consistently produced due to sub10fs pulse formation at TW/cm2 intensities corresponding to an excited carrier density up to 1020cm-3.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)Jan 1, 19980 citations

Dephasing of Coherent Excitations

H. Kalt, Claus F. Klingshirn

Graduate texts in physicsJan 1, 20240 citations

Coherent control of dephasing process and many-body interactions among excitons in GaAs multiple quantum wells

Yoshihiro Ogawa, F. Minami, Naokatsu Yamamoto

Journal of LuminescenceMay 14, 20093 citations

Vibrational dephasing measurements with cw mode-locked dye lasers

J.P. Heritage

Recent advances in the development of synchronously mode-locked dye-laser systems have permitted the first low-power measurement of the time-resolved dephasing dynamics of a Raman active molecular vibration. Excitation and delayed probing of the coherent ensemble of vibrators is accomplished with the help of synchronized picosecond pulse trains from two independently tunable mode-locked dye lasers. A new probe technique, based on a gain measurement, is employed that provides a signal that scales linearly with the coherent vibrational amplitude. We demonstrate this technique with the first measurement of the dephasing dynamics of the normal mode (656.5 cm−1) of CS2 in the liquid state. An exponential decay with time constant 20±1 psec is obtained for the isotropic component of the coherent scattering.Recent advances in the development of synchronously mode-locked dye-laser systems have permitted the first low-power measurement of the time-resolved dephasing dynamics of a Raman active molecular vibration. Excitation and delayed probing of the coherent ensemble of vibrators is accomplished with the help of synchronized picosecond pulse trains from two independently tunable mode-locked dye lasers. A new probe technique, based on a gain measurement, is employed that provides a signal that scales linearly with the coherent vibrational amplitude. We demonstrate this technique with the first measurement of the dephasing dynamics of the normal mode (656.5 cm−1) of CS2 in the liquid state. An exponential decay with time constant 20±1 psec is obtained for the isotropic component of the coherent scattering.

Applied Physics LettersApr 1, 197971 citations

Stable coherent mode-locking based on $\pi$ pulse formation in single-section lasersStable coherent mode-locking based on $$\pi$$ pulse formation in single-section lasers

Rostislav M. Arkhipov, A. V. Pakhomov, Mikhail V. Arkhipov +2 more

Here we consider coherent mode-locking (CML) regimes in single-section cavity lasers, taking place for pulse durations less than atomic population and phase relaxation times, which arise due to coherent Rabi oscillations of the atomic inversion. Typically, CML is introduced for lasers with two sections, the gain and absorber ones. Here we show that, for certain combination of the cavity length and relaxation parameters, a very stable CML in a laser, containing only gain section, may arise. The mode-locking is unconditionally self-starting and appears due to balance of intra-pulse de-excitation and slow interpulse-scale pump-induced relaxation processes. We also discuss the scaling of the system to shorter pulse durations, showing a possibility of mode-locking for few-cycle pulses.Here we consider coherent mode-locking (CML) regimes in single-section cavity lasers, taking place for pulse durations less than atomic population and phase relaxation times, which arise due to coherent Rabi oscillations of the atomic inversion. Typically, CML is introduced for lasers with two sections, the gain and absorber ones. Here we show that, for certain combination of the cavity length and relaxation parameters, a very stable CML in a laser, containing only gain section, may arise. The mode-locking is unconditionally self-starting and appears due to balance of intra-pulse de-excitation and slow interpulse-scale pump-induced relaxation processes. We also discuss the scaling of the system to shorter pulse durations, showing a possibility of mode-locking for few-cycle pulses.

Scientific ReportsJan 13, 20218 citations

Stable coherent mode-locking based on

\pi

pulse formation in single-section lasers