Stimulated Photon Echo Research Articles

Conditions for Using Stimulated Photon Echo to Record and Reproduce Information in Three-Level Systems

The conditions for observing photon echo signals in crystals with excitation and detection in different resonant transitions with a single common energy level are studied. Uncorrelated inhomogeneous broadening in different resonance transitions is shown to influence the formation of stimulated photon echo in three-level systems. Lowering the sample temperature makes it possible to increase the relaxation time, which is used in experiments for observing photon echo. Uncorrelated inhomogeneous broadening in different resonance transitions is temperature independent and affects the intensity of the response at low temperatures, as well. Observation of stimulated photon echo in solid three-level samples requires a correct choice of the time interval between the first and second exciting pulses, but is not related to the magnitude of the irreversible transverse relaxation of the system.

The Image Conversion in Optical Echo-Holography by External Electromagnetic Standing Waves

The recording and playback of information using a reverse stimulated photon—echo hologram when exposed to the recording medium pulse of non-resonant electromagnetic standing wave was considered. It was shown that the spatial intensity distribution in stimulated echo hologram response depended on the electric field intensity of non-resonant standing wave that allowed controlling by a reproducible image.

Collision-induced stimulated photon echo in magnetic field

The action of the longitudinal magnetic field on the collision-induced stimulated photon echo formed on the transition with the angular momentum change is studied theoretically. It is shown that this action depends essentially on the sign of the difference in the orientation and alignment relaxation rates of the excited level b. If , then the echo intensity in a weak magnetic field increases with the increase in the magnetic field strength, while in the alternative case it decreases up to zero value. The formulae enabling the determination of the magnitude of the difference from the experimental study of the oscillations of the echo intensity with the increase in the magnetic field strength are obtained.

Effect of Collisions on the Form of Stimulated Photon Echo in a Gas

The spectral diffusion and time–frequency correlation of an inhomogeneously (Doppler) broadened line in a gas with velocity-changing collisions of particles in addition to the impact of spectral diffusion on the formation of stimulated photon echo (SPE) were investigated. It was shown that the frequency shift of the resonance transition of the gas atoms varied randomly with every velocity-changing collision of the atom. This led to uncorrelated inhomogeneous broadening in the gas at different time points and to a partial loss of the phase memory affecting the photon echo formation. This resulted in a distortion of the SPE temporal shape and; correspondingly, of the reproducibility of the information encoded in the temporal shape of a nonresident laser pulse.

Two-frequency information recording in a three-level system using stimulated photon echo

The process of recording and reproducing information in a three-level system using stimulated photon echo is studied as a function of the amount of information embedded in the first and second two-frequency object laser pulses. It is shown that two-frequency information recording leads to an increase in the power of the stimulated photon echo response on one frequency transition and to its reduction on the other.

How the information-flux density in stimulated photon echo depends on the statistical characteristics of the object laser pulse

This paper discusses how the statistical characteristics of an object laser pulse affect the efficiency with which the information encoded in its temporal shape is reproduced. The dependence of the information-flux density in stimulated photon echo on the area of the object pulse is determined in two-level and three-level systems.

Frequency-Temporal Correlation of Inhomogeneous Broadening for Different Modes of Excitation of Stimulated Photon Echo

The correlation coefficient for isochromatic curves of a laser-excited inhomogeneously broadened line is found to depend on the excitation region. The correlation between the isochromatic curves of an inhomogeneously broadened line over different time intervals in spatially inhomogeneous external electric fields is studied. It is shown that the efficiency with which the stimulated photon echo is locked for different schemes of excitation of the resonance transition depends on the gradients of the spatially inhomogeneous external electric fields and on the width of the excitation region for the inhomogeneously broadened line.

Polarization properties of long-lived stimulated photon echo

The polarization properties of the long-lived stimulated photon echo formed on the transition ja → jb with the atomic levels degenerate in the projections of the angular momenta are studied theoretically. The two particular transitions ja = 1 → jb = 0 and ja = 1 → jb = 1 with degenerate ground state ja = 1 are discussed. For the transitions ja = 1 → jb = 1 the polarizations and areas of the first (‘write’) and the third (‘read’) excitation pulses are found when the echo polarization faithfully reproduces the arbitrary polarization of the weak (single-photon) second (‘information’) pulse, so that this echo scheme may implement the quantum memory for a single-photon polarization qubit, while for the transitions ja = 1 → jb = 0 it is shown, that the echo polarization differs from that of the second pulse at any conditions.

Two-Frequency Information Recording Using Stimulated Photon Echo in a Three-Level System

We study recording of information in a three-level system at external spatially inhomogeneous electric fields in the case of its coding in the first two-frequency object laser pulse. At two-frequency information recording, the temporal shape of a two-frequency object pulse is correlated with stimulated photonecho response. We observe that stimulated photon-echo responses are observed to be locked during the action of an external spatially inhomogeneous electric field between the first and second or after the third two-frequency pulse.

Frequency–time correlation of the inhomogeneous broadening of a resonance line and data-locking efficiency in various setups for exciting a stimulated photon echo

This paper discusses the data-locking efficiency when data is recorded by means of stimulated-photon echo and the dependence of the frequency–time correlation coefficient of inhomogeneous broadening in various regions of the excitation of an inhomogeneously broadened line. It is shown that the rate of change of the correlation coefficient depends on the region of excitation of the inhomogeneously broadened line, as well as on the gradients of the external spatially inhomogeneous electromagnetic fields.

Formation of Stimulated Photon Echo in Three-Level Systems and Recovery of Phase Memory by External Spatially Inhomogeneous Electric Fields

The formation of stimulated photon echo is studied in three-level systems in the presence of external inhomogeneous electric fields. The ratio of the gradients of external spatially inhomogeneous electric fields required to recover the phase memory of the system is calculated. This ratio is found to correlate with the nonequidistance parameter of the spectrum of the system.

Polarization echo spectroscopy of the 0 ↔ 1 transition in ytterbium vapour

Our research into photon echo (PE) and stimulated photon echo (SPE) in ytterbium vapour at the transition 0 ↔ 1 is summarized. We present the polarization properties of PE and SPE in pure gas, anisotropy of collision relaxation, collision-induced PE and collision-induced SPE.

The optimal conditions for the correlation of object pulse temporary form with the stimulated photon echo response in the presence of external spatial inhomogeneous electric fields

The influence of external spatially inhomogeneous electric fields on the reproducibility of the information and effectiveness of stimulated photon echo responses locking at different encoding information in the object laser pulses are investigated.

Effectiveness of Locking a Stimulated Photon Echo in a Three-Level System, Depending on the Mutual Orientation of Standing Waves of Nonresonant Laser Pulses

We consider the effectiveness of locking the stimulated photon echo response in a three-level system, depending on the mutual orientation of external nonresonant electromagnetic standing waves. We show that the effect of locking the stimulated photon echo response depends on the “non-equidistance” parameter for the spectrum of the system.

Recording and reproducing information with various encoding schemes, using stimulated photon echo in a three-level system

This paper discusses how external spatially inhomogeneous electric fields affect information reproduction in the stimulated-photon-echo response in a three-level system when the information is encoded in the temporal shape of the object pulse and in the time intervals of an echelon of laser pulses taken as the object pulse. The information-locking effect for various encoding schemes is investigated for various unequal spacings of the spectrum of a three-level system.

Control of Stimulated Photon-Echo Response Time in a Three-Level System by Changing the Relative Orientation of the External Electric-Field Gradients

We investigate the formation of stimulated photon echo in a three-level system in the presence of spatially inhomogeneous external electric fields. We show the possibility of controlling stimulated photon-echo response time in the nano-temporal range.

Polarization of the stimulated photon echo in ytterbium vapour at the transition 0 ↔ 1

Experimental results were obtained at the inter-combination transition (6s2) 1S0 ↔ (6s6p) 3P1 (type 0 ↔ 1) of 174Y b vapour for several combinations of linear and circular polarizations of three exciting pulses. A peculiar case appears when the first pulse has linear polarization crossed with the polarizations of the second and third exciting pulses: the stimulated photon echo (SPE) does not appear in pure ytterbium; dilution of ytterbium by Xe implies a collision induced SPE with non-monotonic amplitude dependence on buffer pressure, and with polarization along the first exciting pulse. For circular polarizations, when the first exciting pulse has polarization opposite to the circular polarizations of the second and third pulses, the SPE does not appear either in pure ytterbium vapour or in its mixture with a heavy atomic buffer. SPE polarization dependence on the third exciting pulse area was demonstrated. This result may be of interest for optical data processing. All the results agree with theoretical predictions.

Two-Channel Hologram Recording Using Photon Echo in Three-Level Systems

Information recording in three-level systems in external spatially inhomogeneous electric fields with coding of the data in the first two-frequency object pulse is studied. It is shown that when the nonequidistance parameter of the system is <1 the real-time scale in the stimulated photon echo response undergoes changes. When a spatially inhomogeneous electric field is applied between the first and second pulses and after the third pulse, a locking effect is observed in the stimulated photon echo response with an efficiency that depends on the field gradient.

Photon echoes in single- and trilayer semiconductor films of different nanosized thicknesses and their properties

A femtosecond stimulated photon echo is detected for the first time in thin semiconductor films with thicknesses of 100, 800, and 2400 nm. It is established that relaxation time T1 varies with ZnO film thickness, taking values of 0.96, 2.96, and 4.312 ps at thicknesses of 2400, 800, and 100 nm, respectively. For ZnO/Si+/Si− trilayer films, the relaxation time is T1 = 12.73 ps.

Optimum conditions for correlation of the temporal shape of an object pulse with a stimulated photon echo response in inhomogeneous external electric fields

We have studied the information locking effect and the effect of correlation of the shape of an object laser pulse with the shape of a stimulated photon echo response in the presence of external spatially inhomogeneous electric fields. We have shown that, for the transition 3H4-3P0 in a LaF3:Pr3+ crystal, one can observe the effect of the correlation of the shape of an object laser pulse with the shape of a stimulated photon echo response and, depending on the scheme of the action of external spatially inhomogeneous electric fields, either the information locking effect or the information destroying effect.