The effect of the presence of ytterbium (Yb3+) on the upconversion (UC) emission of erbium (Er3+) in yttrium silicate crystalline ceramic powders prepared by combustion synthesis was investigated under continuous wave (cw) near-infrared (λ = 975 nm) laser excitation. UC emission bands centered at ∼380, ∼410, ∼480, ∼530, ∼555 and ∼660 nm were identified, respectively, as 4f–4f transitions from Er3+ excited states 4G11/2, 2H9/2, 4F7/2, 2H11/2, 4S3/2 and 4F9/2. Aiming to photonics applications, the optical temperature sensor performance of this material was also investigated by measurements of the fluorescence intensity ratio of the signals at 530 and 555 nm in the temperature range of 300–600 K. The maximum sensor sensitivity found was ∼56 × 10−4 K−1. We observed that the maximum sensor sensitivity increased to ∼70 × 10−4 K−1 when the cw laser excitation was replaced by a pulsed (∼5 ns) laser excitation. The change in sensor sensitivity is attributed to optical heating of the sample that occurs under cw excitation.

Three-photon upconversion and optical thermometry characterization of Er3+:Yb3+ co-doped yttrium silicate powders

STIRAP (stimulated Raman adiabatic passage) is a powerful laser-based method, usually involving two photons, for efficient and selective transfer of populations between quantum states. A particularly interesting feature is the fact that the coupling between the initial and the final quantum states is via an intermediate state, even though the lifetime of the latter can be much shorter than the interaction time with the laser radiation. Nevertheless, spontaneous emission from the intermediate state is prevented by quantum interference. Maintaining the coherence between the initial and final state throughout the transfer process is crucial. STIRAP was initially developed with applications in chemical dynamics in mind. That is why the original paper of 1990 was published in The Journal of Chemical Physics. However, from about the year 2000, the unique capabilities of STIRAP and its robustness with respect to small variations in some experimental parameters stimulated many researchers to apply the scheme to a variety of other fields of physics. The successes of these efforts are documented in this collection of articles. In Part A the experimental success of STIRAP in manipulating or controlling molecules, photons, ions or even quantum systems in a solid-state environment is documented. After a brief introduction to the basic physics of STIRAP, the central role of the method in the formation of ultracold molecules is discussed, followed by a presentation of how precision experiments (measurement of the upper limit of the electric dipole moment of the electron or detecting the consequences of parity violation in chiral molecules) or chemical dynamics studies at ultralow temperatures benefit from STIRAP. Next comes the STIRAP-based control of photons in cavities followed by a group of three contributions which highlight the potential of the STIRAP concept in classical physics by presenting data on the transfer of waves (photonic, magnonic and phononic) between respective waveguides. The works on ions or ion strings discuss options for applications, e.g. in quantum information. Finally, the success of STIRAP in the controlled manipulation of quantum states in solid-state systems, which are usually hostile towards coherent processes, is presented, dealing with data storage in rare-earth ion doped crystals and in nitrogen vacancy (NV) centers or even in superconducting quantum circuits. The works on ions and those involving solid-state systems emphasize the relevance of the results for quantum information protocols. Part B deals with theoretical work, including further concepts relevant to quantum information or invoking STIRAP for the manipulation of matter waves. The subsequent articles discuss the experiments underway to demonstrate the potential of STIRAP for populating otherwise inaccessible high-lying Rydberg states of molecules, or controlling and cooling the translational motion of particles in a molecular beam or the polarization of angular-momentum states. The series of articles concludes with a more speculative application of STIRAP in nuclear physics, which, if suitable radiation fields become available, could lead to spectacular results.

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Roadmap on STIRAP applications

Slow and stored light induced by electromagnetically induced transparency can enhance the strength of light–matter interaction and enable nonlinear optical processes even at single-photon levels. Here Lee, et al. demonstrate spinor slow light using a double-tripod atom–light coupling scheme.

/pdf/experimental-demonstration-of-spinor-slow-light-aom7zoqkqj.pdf

Experimental demonstration of spinor slow light

We experimentally demonstrate an all-optical routing based on light storage in a Pr3+:Y2SiO5 crystal. Under electromagnetically induced transparency, the optical information of the probe light pulse can be stored in the crystal. By simultaneously switching on two retrieve control fields in the release process, the stored optical information from one light channel can be distributed into two light channels. Such an all-optical routing in solids may have practical applications in quantum information and all-optical network.

All-optical routing by light storage in a Pr3+:Y2SiO5 crystal

Developments in quantum information science rely critically on entanglement—a fundamental aspect of quantum mechanics that causes parts of a composite system to show correlations stronger than can be explained classically. In particular, scalable quantum networks require the capability to create, store and distribute entanglement among distant matter nodes by means of photonic channels. Atomic ensembles can play the role of such nodes. So far, in the photon-counting regime, heralded entanglement between atomic ensembles has been successfully demonstrated through probabilistic protocols. But an inherent drawback of this approach is the compromise between the amount of entanglement and its preparation probability, leading to intrinsically low count rates for high entanglement. Here we report a protocol where entanglement between two atomic ensembles is created by coherent mapping of an entangled state of light. By splitting a single photon and performing subsequent state transfer, we separate the generation of entanglement and its storage. After a programmable delay, the stored entanglement is mapped back into photonic modes with overall efficiency of 17%. Together with improvements in single-photon sources, our protocol will allow ‘on-demand’ entanglement of atomic ensembles, a powerful resource for quantum information science.

http://absimage.aps.org/image/MAR08/MWS_MAR08-2007-007122.pdf

Mapping photonic entanglement into and out of a quantum memory

We experimentally demonstrate the slowing and storage of double light pulses in a Pr3+:Y2SiO5 crystal using a multilevel-tripod scheme. Owing to double dark-state polaritons of the tripod-type system, two signal pulses can be simultaneously slowed. Also, we realize the simultaneous storage (and retrieval) of double light pulses by switching off (and back on) the control field. Slowing and storage of double light pulses in solids may have practical applications in quantum information and quantum networks.

Slowing and storage of double light pulses in a Pr3+:Y2SiO5 crystal.

We experimentally demonstrate light storage and release in a four-level double-lambda atomic system of a Pr 3+:Y2SiO5 crystal. Based on the technique of light storage, we realize optical information transfer between two light channels. The coherent optical information of a probe pulse stored in the crystal can be selectively released into two different light channels by varying the frequency and propagation direction of the switch-on control field.

Optical information transfer between two light channels in a Pr(3+):Y(2)SiO(5)crystal.

We experimentally demonstrate an erasure of stored optical information in a Pr3+:Y2SiO5 crystal by applying an erasing pulse to destroy atomic spin coherence. We observed an erasing efficiency of about 85%. Such an erasing operation of stored optical information may have practical applications in the field of information processing and all-optical network.

Erasure of stored optical information in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an enhanced four-wave mixing (FWM) based on atomic coherence in a Pr3+:Y2SiO5 crystal. By employing coherent population return and fractional stimulated Raman adiabatic passage to prepare maximum atomic coherence in the crystal, an efficient FWM signal can be generated. By measuring the generated FWM signal, the time-dependent atomic coherence is monitored. Such an enhanced FWM in solids may have practical applications in nonlinear optics and laser spectroscopy.

Dun-Mao Du

Papers

All-optical routing by light storage in a Pr3+:Y2SiO5 crystal

Slowing and storage of double light pulses in a Pr3+:Y2SiO5 crystal.

Optical information transfer between two light channels in a Pr(3+):Y(2)SiO(5)crystal.

Erasure of stored optical information in a Pr3+:Y2SiO5 crystal

Enhanced four-wave mixing by atomic coherence in a Pr3+:Y2SiO5 crystal