Self-Compression of High Power Laser Pulses in an Atomic Gas

A. Nazarkin, G. Korn

Lev Khaykovich, Nir Davidson

Kazuya Yamashita, Kouhei Hanasaki, Akihiro Ando +2 more

We report on an all-optical production of a $^{87}\mathrm{Rb}$ Bose-Einstein condensate (BEC) of ${10}^{6}$ atoms. We construct a double compressible crossed dipole trap (DCDT) formed by a high-power multimode fiber laser (MCDT) and a single-mode fiber amplifier (SCDT), which are both operated at $1.06\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$. A very cold dense gas is first cooled by polarization gradient cooling in a three-dimensional optical lattice. More than $2\ifmmode\times\else\texttimes\fi{}{10}^{7}$ atoms are loaded into the enlarged DCDT. Both CDTs are then simultaneously compressed to significantly different sizes followed by evaporation, which is performed by lowering only the MCDT power. The tighter SCDT produces an extremely high collision rate and maintains the trap stiffness, which leads to rapid and efficient evaporation. After 0.4 s, a gas of $5\ifmmode\times\else\texttimes\fi{}{10}^{6}$ atoms with a phase-space density of 0.2 is confined within the SCDT alone. Further evaporation in 2.8 s yields a nearly pure BEC of $1.2\ifmmode\times\else\texttimes\fi{}{10}^{6}$ atoms in the $|F{m}_{F}\ensuremath{\rangle}=|11\ensuremath{\rangle}$ state. This number is the largest generated among all-optical methods. Our approach significantly improves the atom number of a condensate and circumvents the severe atom loss previously reported for multimode fiber lasers.

Vladimir G. Minogin

T. C. H. de Raadt, J. G. H. Franssen, O.J. Luiten

We present the first observation of subpicosecond electron bunches from an ultracold electron source. This source is based on near-threshold, two-step, femtosecond photoionization of laser-cooled rubidium gas in a grating magneto-optical trap. Bunch lengths as short as 735±7 fs (rms) have been measured in the self-compression point of the source by means of ponderomotive scattering of the electrons by a 25 fs, 800 nm laser pulse. The observed temporal structure of the electron bunch depends on the central wavelength of the ionization laser pulse, in agreement with detailed simulations of the atomic photoionization process. This shows that the bunch length limit imposed by the atomic photoionization process has been reached.

Sergey N. Bagaev, Igor B. Mekhov, Чехонин Игорь Анатольевич +1 more

Subject of study. Three-dimensional solitons of the theory of self-induced transparency of laser pulses with a converging cylindrical wavefront and different transverse spatial profiles of the pulse field in 87Rb vapor (resonant transition D2, wavelength 780.24 nm) are studied. Aim of study. The aim is the experimental study of three-dimensional solitons of self-induced transparency of laser pulses for the development of new device prototypes for resonant quantum microwave photonics using laser signal processing methods in the microwave region of the spectrum. Method. In the caustic of a focused beam of a laser pump pulse with a cylindrical wavefront, a transverse spatial profile of the electric field strength of a special shape is created. The computer-generated holograms developed by us can be used to create an arbitrary profile. Main results. The properties of a three-dimensional self-induced transparency soliton are studied for various detuning frequencies of the input pulse field with respect to atomic resonance. The maximum laser pulse power is 8.5 mW, the pulse duration is 4–5 ns, and the time resolution of the recording system is 27 ps. It is shown that the all-optical control of the carrier frequency of the input pulse determines the properties of the output pulse: compression of the pulse duration (generation of a strobe pulse), the value of the soliton delay in time, and the time shift of the carrier frequency of the soliton. Practical significance. The results obtained in this study of the properties of three-dimensional self-induced transparency solitons will serve as the basis for the development of prototypes of signal processing devices using low-power laser diodes.