Observation of the 0π Pulse

Masataka Nakazawa, Kazunori Suzuki, Yasuo N. Kimura +1 more

Coherent \ensuremath{\pi}-pulse propagation with pulse breakup has been observed in an erbium-doped fiber waveguide amplifier. The waveguide was pumped by a 1.48-\ensuremath{\mu}m ${\mathrm{In}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ga}}_{\mathit{x}}$${\mathrm{As}}_{\mathit{y}}$${\mathrm{P}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$ laser diode. The waveguide had an erbium ion concentration of 8900 ppm and was cooled to 4.2 K. The pulse source was a 1.53-\ensuremath{\mu}m mode-locked Er-doped glass laser with a pulse width of 400 ps. A pulse advance of approximately 130 ps was observed between a low-intensity transmitted pulse with a low pump power and an amplified \ensuremath{\pi} pulse in a 1.5-m-long fiber.

John A. Armstrong, E. Courtens

A. P. Gavrilyuk, I. V. Krasnov

Oleg M. Parshkov

The interaction of a sufficiently intense 0 π pulse with the inhomogeneously broadened resonance quantum transition is studied numerically in the slowly varying envelope approximation. The formation of a single optical breather and evolution of the population of energy levels related to it are described. It is found that in the quasi-resonance case, two 2 π pulses of the same duration with different frequencies appear instead of the breather at a large distance. The frequency modulation also prevents the formation of the breather, giving rise to one 2 π pulse or two 2 π pulses of different frequencies and different durations. The results of numerical analysis of the known experiment on the observation of the 0 π pulse in a ruby crystal are presented. It is shown that due to the presence of irreversible relaxation in this experiment, an optical breather was detected at the stage of its transformation to a weak 0 π pulse.

Joshua E. Rothenberg, D. Grischkowsky, Anne C. Balant

In coherent optics the pulse area θ is defined as the total angle the atomic state vector rotates around the electric field of the resonant driving pulse. The atomic excitation remaining after passage of the pulse is determined by this angle. For example, a π/2 pulse will put the atoms in a coherent superposition of the ground and excited states, a π pulse will put the atoms in the excited state, and a 2π pulse will take the atoms to the excited state and then back to the ground state. Another type of pulse which has generated a considerable amount of theoretical interest1 but for which there has been only a few experimental investigations2 is the 0π pulse. For this pulse, the initial part of the pulse excites the atoms and then due to a phase change of π in the electric field, the latter part of the pulse takes the atoms back to the ground state. Thus, just as in self-induced transparency, the atoms are completely in the ground state after passage of the pulse. There are two ways to produce such a 0π pulse. The first is to switch the phase of the second half of the pulse by electro-optic techniques. For this method it is difficult to get the 0π pulse area to the desired accuracy. The second method is to rely on the automatic reshaping to the 0π pulse which occurs when a weak (θ(t) ≪ 1) pulse is propagated through a resonant vapor. This method will produce the 0π pulse area to any desired degree of accuracy. This fact is due to an area theorem for these weak pulses which states that the pulse area decays exponentially with the on-resonance absorption coefficient.1

C. Luciuk, Scott Smale, Stefan Trotzky +3 more