Biological tissue is a highly scattering medium that prevents deep imaging of light. For medical applications, optical imaging offers a molecular sensitivity that would be beneficial for diagnosing and monitoring of diseases. Acousto-optical tomography has the molecular sensitivity of optical imaging with the resolution of ultrasound and has the potential for deep tissue imaging. Here, we present a theoretical study of a system that combines acousto-optical tomography and slow light spectral filters created using spectral hole burning methods. Using Monte Carlo simulations, a model to obtain the contrast-to-noise ratio (CNR) deep in biological tissue was developed. The simulations show a CNR > 1 for imaging depths of ∼5 cm in a reflection mode setup, as well as, imaging through ∼12 cm in transmission mode setups. These results are promising and form the basis for future experimental studies.
Solid state quantum computer hardware may be based on rare-earth-ion-doped crystals. The qubits can
be encoded as nuclear spin states of an ensemble of, e.g., Pr3+ ions, randomly doped into a Y2SiO5 crystal.
Two such qubits can control each other through the dipole blockade effect, and transfers between the two
qubit states can be done at a high fidelity, despite the strongly inhomogeneous nature of the ensemble
approach. In this paper full control over the qubit Bloch sphere is demonstrated, by performing arbitrary
qubit rotations and characterizing the outcomes using quantum state tomography.
In photon-echo-based optical data storage and data processing the photon echo output intensity generally is about 0.1 - 1% of the input intensity. Many devices, such as processors would require that the photon echo output is used as an input to a new photon echo process. To obtain a sufficient signal-to- noise it would be necessary to first amplify the photon echo output signal. In this paper Pr-doped ZBLAN fibers are used to amplify the photon echo signals generated in Pr-doped Y2SiO5 at 606 nm. The fiber amplifier is pumped by the 476 nm output from an Ar-ion laser. Mirror-less lasing due to reflection at the fiber ends is eliminated by cleaving the fiber ends at an angle. The upper limit of the gain in a fiber is set by the core refractive index and the fiber numerical aperture. By changing from a fiber with numerical aperture of 0.4 to one with 0.15, the gain obtained at 606 nm is increased from 45 to 330.