No abstract

The absorption of traveling photons resonant with electric dipole transitions of an atomic gas naturally leads to electric dipole spin wave excitations. For a number of applications, it would be highly desirable to shape and coherently control the spatial waveform of the spin waves before spontaneous emission can occur. This work details a recently developed optical control technique to achieve this goal, where counter-propagating, shaped sub-nanosecond pulses impart sub-wavelength geometric phases to the spin waves by cyclically driving an auxiliary transition. In particular, we apply this technique to reversibly shift the wave vector of a spin wave on the D2 line of laser-cooled 87 Rb atoms, by driving an auxiliary D1 transition with shape-optimized pulses, so as to shut off and recall superradiance on demand. We investigate a spin-dependent momentum transfer during the spin-wave control process, which leads to a transient optical force as large as ∼ 1 k/ns, and study the limitations to the achieved 70 ∼ 75% spin wave control efficiency by jointly characterizing the spin-wave control and matterwave acceleration. Aided by numerical modeling, we project potential future improvements of the control fidelity to 99% level when the atomic states are better prepared and by equipping a faster and more powerful pulse shaper. Our technique also enables a backgroundfree measurement of the superradiant emission to unveil the precise scaling of the emission intensity and decay rate with optical depth for the first time to our knowledge.

Advances of quantum control technology have led to nearly perfect single-qubit control of nuclear spins and atomic hyperfine ground states. In contrast, quantum control of strong optical transitions, even for free atoms, are far from being perfect. Developments of such quantum control appears to be limited by available laser technology for generating isolated, sub-nanosecond optical waveforms with 10's of GHz programming bandwidth. Here we propose a simple and robust method for the desired pulse shaping, based on precisely stacking multiple delayed picosecond pulses. Our proof-of-principal demonstration leads to arbitrarily shapeable optical waveforms with 30 GHz bandwidth and 100 ps duration. We confirm the stability of the waveforms by interfacing the pulses with laser-cooled atoms, resulting in “super-resolved” spectroscopic signals. This pulse shaping method may open exciting perspectives in quantum optics, and for fast laser cooling and atom interferometry with mode-locked lasers.

In the present study, a solid self‐emulsification delivery system (S‐SEDS) is developed to improve the bioavailability of astaxanthin (ASX). The pseudo ternary phase diagram method is used to screen the optimum composition of liquid self‐emulsification delivery system (SEDS). This liquid system is converted into solid state using the solid absorbent carrier by simple physical mixing. Through the analysis of powder flowability and adsorption capacity, silicon dioxide and anhydrous calcium hydrogen phosphate are selected as solid carriers of the liquid self‐emulsification system. Results of Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) indicate that astaxanthin is encapsulated in these solid carriers. In the in vitro dissolution study, sustained release of astaxanthin from two different ASX‐SEDS (prepared with silicon dioxide and anhydrous calcium hydrogen phosphate) is obtained and the cumulative release is correspondingly 51.06 ± 0.98 and 49.97 ± 0.87% within 2 h. A delayed pattern of absorbed ASX‐SEDS is observed in the study with anhydrous calcium hydrogen phosphate compared to the counterpart with silicon dioxide, which is consistent with the result from the in vitro digestion study. Antioxidant study shows that astaxanthin can be encapsulated in S‐SEDS without the loss of antioxidant activity. Consequently, S‐SEDS can be a promising vehicle in food industry. Practical Applications: Traditionally, liquid‐based delivery systems are prepared using liquid components, which have some disadvantages, such as, complex production process, low active ingredient loading, narrow application range, and lacking of effective evaluation methods. The present study adopts physical adsorption, a gentle and simple process, to prepare the solid self‐emulsifying system. This system combines the advantages of liquid‐based systems and solid dosage forms, which can improve the solubility of poorly solubility active ingredient in intestinal environments, and the high solubility of active ingredient is favor to its absorption. In the present work, the active ingredients solubilization capability of solid formulations is evaluated by in vitro dissolution and digestion studies. It can be seen that over 40% of astaxanthin are released from solid self‐emulsifying systems in 120 min. After the process of digestion, the bioaccessibility reaches 10%. The results of in vitro dissolution and digestion show that after solid adsorption, astaxanthin exhibits delayed release patterns. All the studies demonstrate that solid self‐emulsifying system is an appropriate strategy to improve the bioavailability of astaxanthin. The pseudo ternary phase diagram method is used to screen the optimum composition of liquid self‐emulsification delivery system. Then, this liquid system is converted into solid state using the solid absorbent carrier by simple physical mixing.

The present study was aimed at formulating and evaluating a novel solid self-emulsifying delivery system (S-SEDS) for the application in functional foods of dihydromyricetin (DMY). First, solubility study and pseudo-ternary phase diagram analysis were adopted to optimize the formulation of liquid self-emulsifying delivery system (L-SEDS). And the thermodynamic stable L-SEDS with 5% content of DMY was fabricated and further developed into a solid form via vacuum rotary evaporation with Aerosil 300 as the solid adsorbent. Solid state characterization of the S-SEDS was performed by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray powder diffraction. Furthermore, studies proved that the antioxidant activity and bioaccessibility of DMY were improved after incorporated into S-SEDS formulation compared to pure DMY. The S-SEDS showed good resistance against various storage conditions investigated for 10 weeks.Practical Application: Solid self-emulsifying delivery system (S-SEDS) combined the advantages of liquid self-emulsifying delivery system with those of a solid dosage form to overcome the disadvantages associated with liquid formulations is more convenient for storage and transportation in practical application. Furthermore, the technology of producing S-SEDS is simple and can be realized in industrial production. Hence, S-SEDS could be a promising strategy to overcome the poor water solubility and short biological half-life of dihydromyricetin for further application in functional foods and beverage industry.