Economical Laue x-ray diffraction using photographic film and orientation of single crystals.

Many Laue x-ray diffraction systems using the Polaroid XR-7 Land Diffraction Cassette camera became inactive after production of the required high sensitivity Polaroid T-57 instant film ceased. This Tutorial reports on a low-cost solution using the readily available replacement film with push processing to increase the effective film speed. The use of this film in the polaroid camera is described along with film development and digitization. The orientation of single crystals with the obtained data and free software is explained. A simple method to prepare single crystals with surfaces perpendicular to a desired crystallographic orientation is described. The content of this Tutorial may prove beneficial for educational and research laboratories.

Properties of a Rare-Earth-Ion-Doped Waveguide at Sub-Kelvin Temperatures for Quantum Signal Processing.

We characterize the 795 nm ^{3}H_{6} to ^{3}H_{4} transition of Tm^{3+} in a Ti^{4+}:LiNbO_{3} waveguide at temperatures as low as 800 mK. Coherence and hyperfine population lifetimes-up to 117 µs and 2.5 h, respectively-exceed those at 3 K at least tenfold, and are equivalent to those observed in a bulk Tm^{3+}:LiNbO_{3} crystal under similar conditions. We also find a transition dipole moment that is equivalent to that of the bulk. Finally, we prepare a 0.5 GHz-bandwidth atomic frequency comb of finesse >2 on a vanishing background. These results demonstrate the suitability of rare-earth-ion-doped waveguides created using industry-standard Ti indiffusion in LiNbO_{3} for on-chip quantum applications.

Tm 3+ Tm 3+ : Y3Ga5O12 materials for spectrally multiplexed quantum memories.

We investigate the relevant spectroscopic properties of the 795 nm (3)H(6)↔(3)H(4) transition in 1% Tm(3+):Y(3)Ga(5)O(12) at temperatures as low as 1.2 K for optical quantum memories based on persistent spectral tailoring of narrow absorption features. Our measurements reveal that this transition has uniform coherence properties over a 56 GHz bandwidth, and a simple hyperfine structure split by ± 44 MHz/T with lifetimes of up to hours. Furthermore, we find a (3)F(4) population lifetime of 64 ms-one of the longest lifetimes observed for an electronic level in a solid--and an exceptionally long coherence lifetime of 490 µs--the longest ever observed for optical transitions of Tm(3+) ions in a crystal. Our results suggest that this material allows realizing broadband quantum memories that enable spectrally multiplexed quantum repeaters.

Exceptionally narrow homogeneous linewidth in erbium-doped glasses.

We show that rare-earth (RE-) doped glasses can have homogeneous linewidths as narrow as 287 kHz at (4)He temperatures. This is far narrower than others reported in glasses in the same temperature range and is suitable for precise spectral hole burning and spatial-spectral holographic applications. It is known that cw spectral hole burning linewidth measurements of RE ions in glasses are hindered by the presence of spectral diffusion but, even in glasses, application of a magnetic field can freeze out RE spin-spin interactions responsible for spectral diffusion and isolate the remaining contribution of two-level systems (TLSs). The Er(3+):2G2S glasses have unusually low TLS contributions, making it possible to study the real homogeneous linewidth using photon echo measurements. The contribution from TLSs is only 170 T(1.3) kHz when subjected to a field of 5 T.

Optical decoherence in eR3+-doped silicate fiber: evidence for coupled spin-elastic tunneling systems.

We measured the optical decoherence times T2, or, equivalently, the homogeneous line width, in an Er-doped optical fiber at low temperature as a function of external magnetic field and temperature using two-pulse photon echoes. The decoherence times were up to 230 ns at fields above 3 T. The magnitude of the line narrowing induced by a magnetic field of 3 T is 2.5 MHz, which is anomalously large compared to that typical for oxide crystals with similar Er3+ concentration. This is interpreted as evidence for dephasing by coupled spin-elastic tunneling modes where the normal glass tunneling modes acquire a magnetic character by coupling to the Er3+ spin.

Programmable laser frequency stabilization at 1523 nm by use of persistent spectral hole burning.

Diode laser frequency stability of 2 kHz to 680 Hz over 20 ms to 500 s has been demonstrated at 1523 nm in the technologically important communication band by use of persistent spectral holes in the inhomogeneously broadened 4I15/2 --> 4I13/2 optical absorption of Er3+:D-:CaF2. Laser frequency stabilization was realized without vibrational or acoustical isolation of either the laser or spectral hole frequency reference, providing the means for implementing a versatile, compact, stable source.

Spatial-spectral holographic correlator at 1536 nm using 30-symbol quadriphase- and binary-phase-shift keyed codes.

Optical 30-symbol quadriphase-shift keyed (QPSK) and binary-phase-shift keyed (BPSK) codes were processed in a spatial-spectral holographic correlator with the Er(3+): Y(2)SiO(5) spectral hole-burning material operating at 1536 nm in the important 1550-nm communications band. The results demonstrate the ability of spatial-spectral holographic correlators to process QPSK codes and BPSK codes with the same apparatus. The high-fidelity correlations produced by this optical coherent transient device exhibit the low sidelobe characteristics expected for the codes used.

Programmable frequency reference for subkilohertz laser stabilization by use of persistent spectral hole burning.

We report what is believed to be the first demonstration of laser frequency stabilization directly to persistent spectral holes in a solid-state material. The frequency reference material was deuterated CaF(2): Tm(3+) prepared with 25-MHz-wide persistent spectral holes on the H(6)(3)?H(4)(3) transition at 798 nm. The beat frequency between two lasers that were independently locked to persistent spectral holes in separate crystal samples showed typical root Allan variances of 780+/-120Hz for 20-50-ms integration times.

Demonstration of real-time address header decoding for optical data routing at 1536nm.

We have demonstrated real-time decoding of 20-bit biphase-coded address header pulses, using stimulated photon echoes in a phase-matched crossed-beam configuration. This decoding is one of the functions required for coherent transient optical data routing, packet switching, and processing. The active medium used was single-crystal Y(2)SiO(5) doped with Er(3+), which provides an operating wavelength of 1536 nm.

Measurement of photon echoes in ErY(2)SiO(5) at 1.5 microm with a diode laser and an amplifier.

We have measured the optical dephasing time of Er(3+) transitions near 1.5 microm in the two crystallographically inequivalent sites of Y(2)SiO(5), using an external-cavity diode laser amplified by an erbium-doped fiber amplifier. Two-pulse photon echoes were observed at zero field and in magnetic fields up to 55kG, with dephasing times as long as 580 micros (corresponding to a linewidth of 550 Hz). Stimulated echoes were also measured and showed evidence of spectral diffusion during the 13-ms lifetime of the (4)I(13/2) level.

Optical dephasing mechanisms in Tm(3+):Y(2)Si(2)O(7).

Optical dephasing measurements are reported for Tm(3+):Y(2)Si(2)O(7) as a function of temperature and laser excitation intensity. By use of photon echoes, a coherence time of T(2) = 23 micros was measured at 1.24 K for the (3)H(6)(1) ? (3)H(4)(1) transition at 790.427 nm, corresponding to a homogeneous linewidth of 14 kHz. The relatively broad inhomogeneous linewidth of 100 GHz gives an inhomogeneous-to-homogeneous linewidth ratio of Gamma(inh)/Gammah = 7 x 10(6). This large ratio, a transition wavelength suitable for GaAlAs semiconductor lasers, and the absence of hyperfine structure hole burning make this material a good candidate for time-domain signal processing and transient optically addressed data storage.

Ligation and quaternary structure induced changes in the heme pocket of hemoglobin: a transient resonance Raman study.

The extent to which ligation and quaternary structure modify the heme-heme pocket configuration is determined by generating and analyzing transient resonance Raman spectra from various photolyzed and partially photolyzed hemoglobins (Hb). From small frequently shifts in Raman band I (approximately 1355 cm-1) it is determined that ligation induces a configurational change about the heme. The extent to which ligation modifies the heme pocket is influenced by the quaternary structure. With respect to the structural parameter responsible for variations in the pi orbital electron density of the porphyrin, the degree of alteration of the heme pocket configuration relative to deoxy-Hb(T) follows the sequence: liganded Hb(R) greater than liganded Hb(R) + IHP greater than liganded Hb(T) [alpha chain greater than beta chain] greater than deoxy-Hb(R). This progression of configurations also forms a sequence with respect to the "retentiveness" of the heme pocket as reflected in the ligand dynamics associated with geminate recombination. The results indicate that the heme-heme pocket of the R-state Hb's, relative to those of the T-state species, favors ligand retention in a dynamic, as well as thermodynamic, sense. The analysis of these and other related data implicates a ligation and quaternary structure modulated electronic and/or electrostatic interaction between the pi system of the porphyrin and the surrounding heme pocket as the basis for this variation in ligand dynamics as well as for the energetics of cooperativity.

Narrowed intermediate resonance in multiresonant four-wave mixing in LiTbF(4).

A new technique for overcoming inhomogeneous broadening in condensed matter is reported. Phase-matchinginduced frequency selectivity associated with multiresonant four-wave mixing is explored in detail for the first time to our knowledge and shown to give laser-limited linewidths that are more than 10 times narrower than the inhomogeneous width of an intermediate resonance in LiTbF (4). The anomalous dispersion associated with the resonance. was also measured, and model calculations suggest that significantly greater narrowing is feasible.

The mechanism of DNA strand breakage by vitamin C and superoxide and the protective roles of catalase and superoxide dismutase.

Vitamin C breaks DNA only in the presence of oxygen. Superoxide dismutase has no effect on the reaction but catalase suppresses it. Superoxide also gives rise to breaks in DNA suppressible by both superoxide dismutase and catalase. The hydroxyl radical seems to be the agent responsible for strand cleavage itself.