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Journal of Physics Conference Series

Coherent tunable diffractional pulse shaping and generation of the 0π-pulse in Rb vapor

Sergei N Bagayev, Valentin Averchenko, Чехонин Игорь Анатольевич, M A Chekhonin, I M Balmaev, Igor B. Mekhov

Published Dec 1, 2021• 0 citations
Publisher

Abstract

Abstract We have experimentally studied for the first time a new operation principle of the coherent diffractional pulse shaper (Rabi shaper). In the experiment, we observed an effect of tunable pulse shaping of nanosecond semiconductor laser pulse during the resonant pumping of the D2 line (780.24 nm) of 87Rb vapor in the range of self-diffraction angles φ = ± 4°. We observed the synthesis of nanosecond 0π-pulses at the small length of the nonlinear interaction 0.1…1 mm. We propose to use the Rabi shaper as an energy efficient tunable shaper of classical and single-photon wave packets. We analyze a possibility of the Rabi shaper operation in quantum systems with feedback.

DOI
10.1088/1742-6596/2086/1/012133

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Journal of Physics Conference Series•Dec 1, 2020•0 citations

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Subject of study. The self-diffraction process of a resonant pulse in a dense extended resonant medium was studied for the first time to our knowledge. This process leads to an angular deflection of the output radiation and sequential emission of a large series of N pulses with a variable area in the range (−3π,…,0,…,3π). The pulses are emitted from a small focusing region (0.1–1 mm) of the pump pulse in a dense extended resonant medium. The pulse wavelength corresponds to the resonant transition D287Rb (wavelength 780.24 nm). Aim of study. The nonlinear effect of the self-diffraction of a laser pulse with a cylindrical wavefront is studied in an extended resonant medium of rubidium vapor to develop new resonant microwave photonics devices using laser signal-processing methods in the microwave spectrum. Method. A transverse spatial profile of the electric field strength of a special shape f(x) is created in the caustic of a focused beam of a laser pump pulse with a cylindrical wavefront. The pump pulse must have a converging (for example, cylindrical) wavefront. Computer-synthesized holograms developed by us are used to create an arbitrary f(x) profile. Main results. The effect of the self-diffraction of a pump pulse is studied. This is accompanied by the emission of a series of N coherent resonant pulses with different areas in the range (−3π,…,0,…,3π) from a short focusing region (0.1–1 mm) of a resonant laser pump pulse. The self-diffraction of the pump pulse resulted in 16 emitted pulses with different areas. The distribution of series pulses over the diffraction angle was observed in the angle range from −5∘ to +4∘. The nonlinear generation of 0π-pulses was observed at some angles. The results verify the nonlinear generation of 0π-pulses over a short interaction length between light and a resonant medium for the first time to our knowledge. Practical significance. The obtained results on the effect of the self-diffraction of a resonant pulse with a transverse spatial profile f(x) will serve as a basis for the development of prototype devices for signal-processing problems using low-power laser diodes.

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Femtosecond-pulse two-photon resonant difference-frequency mixing in gases: A technique for tunable vacuum-ultraviolet femtosecond-pulse generation and a spectroscopic tool for studying atoms in strong laser fields

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Physical Review A•Jul 1, 1997•19 citations
Abstract We have experimentally studied for the first time a new operation principle of the coherent diffractional pulse shaper (Rabi shaper). In the experiment, we observed an effect of tunable pulse shaping of nanosecond semiconductor laser pulse during the resonant pumping of the D2 line (780.24 nm) of 87Rb vapor in the range of self-diffraction angles φ = ± 4°. We observed the synthesis of nanosecond 0π-pulses at the small length of the nonlinear interaction 0.1…1 mm. We propose to use the Rabi shaper as an energy efficient tunable shaper of classical and single-photon wave packets. We analyze a possibility of the Rabi shaper operation in quantum systems with feedback.
Abstract We have experimentally studied for the first time a new operation principle of the all-optical coherent streak-camera (Rabi deflector). In the experiment, we observed an effect of significant dynamical angular deflection of a pulse of semiconductor laser during the resonant pumping of the D2 line (780.24 nm) of 87Rb vapor in the range of diffraction angles ϕ = ± 5.45°. We propose to use the Rabi deflector as an energy efficient shaper of classical and single-photon wave packets. We analyze a possibility of the Rabi deflector operation in quantum systems with feedback.
Subject of study. The self-diffraction process of a resonant pulse in a dense extended resonant medium was studied for the first time to our knowledge. This process leads to an angular deflection of the output radiation and sequential emission of a large series of N pulses with a variable area in the range (−3π,…,0,…,3π). The pulses are emitted from a small focusing region (0.1–1 mm) of the pump pulse in a dense extended resonant medium. The pulse wavelength corresponds to the resonant transition D287Rb (wavelength 780.24 nm). Aim of study. The nonlinear effect of the self-diffraction of a laser pulse with a cylindrical wavefront is studied in an extended resonant medium of rubidium vapor to develop new resonant microwave photonics devices using laser signal-processing methods in the microwave spectrum. Method. A transverse spatial profile of the electric field strength of a special shape f(x) is created in the caustic of a focused beam of a laser pump pulse with a cylindrical wavefront. The pump pulse must have a converging (for example, cylindrical) wavefront. Computer-synthesized holograms developed by us are used to create an arbitrary f(x) profile. Main results. The effect of the self-diffraction of a pump pulse is studied. This is accompanied by the emission of a series of N coherent resonant pulses with different areas in the range (−3π,…,0,…,3π) from a short focusing region (0.1–1 mm) of a resonant laser pump pulse. The self-diffraction of the pump pulse resulted in 16 emitted pulses with different areas. The distribution of series pulses over the diffraction angle was observed in the angle range from −5∘ to +4∘. The nonlinear generation of 0π-pulses was observed at some angles. The results verify the nonlinear generation of 0π-pulses over a short interaction length between light and a resonant medium for the first time to our knowledge. Practical significance. The obtained results on the effect of the self-diffraction of a resonant pulse with a transverse spatial profile f(x) will serve as a basis for the development of prototype devices for signal-processing problems using low-power laser diodes.
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.
Creating and controlling well-defined single-photon states is important for many quantum enhanced technologies. Information can be encoded in any degree of freedom associated with a single-photon field excitation, for example in the polarization or transverse spatial mode structure. The ability to encode multiple qubits in these states is desirable for high data transmission rates and increased information processing capacity. The spectral-temporal domain offers a large Hilbert space for encoding information, well suited to integrated optical architectures owing to the low cross-talk between channels. Indeed, time-frequency encoding is an integral component of existing information technologies infrastructure. Thus, complete, coherent control of the spectral-temporal mode structure of light is essential to advancing optical quantum technologies. Arbitrary control of single-photon states has been demonstrated in the polarization and spatial-momentum degrees of freedom however, is yet to be established in the spectral-temporal domain. Recently it was shown that spectral-temporal pulse shaping is experimentally feasible using nonlinear optical methods. However, such techniques can introduce noise photons, are challenging to implement deterministically and require specially prepared auxiliary pump pulses. Furthermore, they are typically only possible at relatively low repetition rates to avoid damage of nonlinear optical materials. Here, we demonstrate deterministic pulse shaping of single-photon wave packets by introducing a time-varying phase. Applying linear or quadratic phase to the wave packet introduces a spectral shift or spectral broadening, respectively. Achieving significant spectral manipulation requires temporal-phase modulation on the order of π. The phase must also vary on the same time scale as the optical pulses, approximately 1 ps in duration here. This relatively rapid phase variation is achieved using a fast electro-optic phase modulator. The modulator is driven by a time-varying voltage that is synchronized with a pulse train of single-photon wave packets for accurate temporal phase control. In this thesis, we experimentally demonstrate control of the spectral-temporal state of single-photon wave packets using this method. Heralded single-photon wave packets are generated by spontaneous parametric down conversion pumped by a frequency-doubled Titanium-Sapphire laser oscillator with 80 MHz repetition rate. To achieve significant modulation of single-photon pulses a 10 V peak-to-peak radio-frequency signal of 40 GHz drives the phase modulator, which requires approximately 3.6 V to achieve a π phase shift. The signal is synchronized with the oscillator pulse train using custom designed electronics. Details of these electronics are presented, resulting in a robust phase and amplitude controllable 40 GHz voltage source, phase locked to the single-photon pulse train. To demonstrate the utility of this pulse-shaping method we experimentally show spectral shearing of almost 1 nm for single-photon wave packets with 830 nm central wavelength and 1 nm bandwidth. Measurement of the second-order intensity correlation before and after the wave-packet manipulation remains constant within uncertainty of the measurement, showing that the quantum nature of the single-photon source is not deteriorated by the modulator. Preservation of the wave-packet coherence is verified by two-photon interference between spectrally sheared and non-modulated single-photons.
We investigate the time dynamics of a four-level rubidium atomic system excited by a train of $0\ensuremath{\pi}$ pulses. Resonant $0\ensuremath{\pi}$ pulse shaping is achieved by propagation of weak femtosecond pulses through rubidium vapor and characterized using frequency-resolved optical gating and within the linear dispersion theory. The excitation of the Rb atoms by $0\ensuremath{\pi}$ pulse train is studied experimentally by modified direct frequency comb spectroscopy and theoretically within the density-matrix approach. We show that accumulation of populations and coherences, as typical pulse train excitation effects, strongly depend on the strength of the resonant $0\ensuremath{\pi}$ pulse shaping. Stronger pulse shaping reduces the coherent accumulation effects, eventually leading to the disappearance of the velocity selective optical pumping observed in the frequency domain.
Two-photon resonant and near-resonant four-wave difference-frequency mixing in gases in the interaction regime when laser pulse durations are comparable to or shorter than the medium polarization relaxation time ${T}_{2}^{\ensuremath{'}}$ is investigated. The results of experimental studies of the process in Ar and Kr using pump pulses from the ArF-excimer laser are presented demonstrating a generation of tunable short pulse radiation in the range 102--124 nm. The results are discussed in terms of a theoretical model based on a self-consistent solution of the Bloch equations for the atomic transitions and the Maxwell equations for the fields. This enables one to interpret specific nonstationary resonant and quasiresonant phenomena involved in the frequency conversion process. It is shown that the femtosecond-pulse four-wave frequency-mixing technique with probe pulses significantly shorter than the pump pulses makes it possible to study the coherent dynamics of an atomic transition exposed to an intense field. Using atomic Kr as the nonlinear medium, coherent Rabi oscillations and the subsequent phase relaxation of excitation were observed under the condition of two-photon interaction of Kr with femtosecond 193-nm laser pulses. The obtained information is important for controlling and optimizing processes of two-photon resonant frequency conversion and for time-resolved studies of Rydberg states in atoms and molecules.