Jing-Feng Liu

Effects of metal ions on simultaneous production of glucose oxidase and catalase by Aspergillus niger

J.‐Z. LIU, Y.‐Y. HUANG, J. LIU, L.‐P. WENG AND L.‐N. JI. 2001. The effects of various metal ions on the simultaneous production of glucose oxidase and catalase by Aspergillus niger were investigated. Calcium carbonate induced synthesis of both enzymes. The induction of calcium carbonate was accompanied by a metabolic shift from the glycolytic pathway (EMP, Embden‐Meyerhof‐Parnas) to direct oxidation of glucose by glucose oxidase. The time course of the biosynthesis of both enzymes is reported. The logistic model was in good agreement with the experimental growth results. The production of both enzymes was growth‐associated. Finally, a model of growth and product formation was also proposed.

Enhancement of spontaneous emission in three-dimensional low refractive-index photonic crystals with designed defects

In this work, we demonstrate that low refractive-index three-dimensional photonics crystals with a planar defect, fabricated with the direct laser writing method, can be used to effectively enhance the spontaneous emission (SE) of semiconductor quantum dots (QDs). To achieve this, we develop a controllable and reliable method to integrate quantum dots into the defect-embedded photonic crystals (PCs). Although the overlapping of different direction stop gaps in low refractive-index defect-free three-dimensional photonic crystals imposes a challenge to realize spontaneous emission enhancement at the band edge wavelength, we achieve a 15% enhancement of the spontaneous emission by introducing a tailored planar defect.

Lifetime distribution of spontaneous emission from emitter(s) in three-dimensional woodpile photonic crystals

Spontaneous emission lifetime distribution in the basic unit cell or on a plane of the excited emitters embedded in woodpile photonics crystals with low refractive index contrast are investigated. It is found that the spontaneous emission lifetime distribution strongly depends on the position and transition frequency of the emitters, and has the same symmetry as that of the unit cell. The lifetimes of emitters near the upper gap edge are longer than that in the center of the pseudo-gap, which is quite a contrast to the conventional concept. Furthermore, it is revealed that the polarization orientation of the emitters has significant influence on the lifetime distribution, and may result in a high anisotropy factor (defined as the difference between the maximum and minimum values of the lifetime) up to 4.2. These results may be supplied in probing the lifetime distribution or orientation-dependent local density of states in future experiments.

Vacuum Rabi splitting in a coupled system of single quantum dot and photonic crystal cavity: effect of local and propagation Green’s functions

We investigate the light emission characteristics for single two level quantum dot (QD) in a realistic photonic crystal (PC) L3 cavity based upon the local coupling strength between the QD and cavity together with the Greens function in which the propagation function related to the position of the detector is taken into account. We find for a PC cavity that the line shape of the propagation function in frequency domain is identical to that of the cavity and independent on the detectors position. We confirm that this identity is not influenced by the horizontal decay of the cavity. Furthermore, it is revealed that the vacuum fluorescence spectrum of the coupled system never give the triplet in strong coupling regime. Our work demonstrates that the experimental spectral-triplet in coupled system of single QD and PC cavity cannot be individually understood by vacuum Rabi splitting without including other physics mechanism.

Slab thickness tuning approach for solid-state strong coupling between photonic crystal slab nanocavity and a quantum dot

The quality factor and mode volume of a nanocavity play pivotal roles in realizing the strong coupling interaction between the nanocavity mode and a quantum dot. We present an extremely simple method to obtain the mode volume and investigate the effect of the slab thickness on the quality factor and mode volume of photonic crystal slab nanocavities. We reveal that the mode volume is approximatively proportional to the slab thickness. As compared with the previous structure finely optimized by introducing displacement of the air holes, via tuning the slab thickness, the quality factor can be enhanced by about 22%, and the ratio between the coupling coefficient and the nanocavity decay rate can be enhanced by about 13%. This can remarkably enhance the capability of the photonic crystal slab nanocavity for realizing the strong coupling interaction. The slab thickness tuning approach is feasible and significant for the experimental fabrication of the solid-state nanocavities.

Spontaneous emission enhancement with defects in a three dimensional pseudo-gap photonic crystal

It is challenging to achieve spontaneous emission enhancement in three-dimensional photonic crystals with pseudo-gaps. By inducing a plane defect, the local density of states were effectively changed leading to 15% decrease of the emission lifetime

Strong anisotropic lifetime orientation distributions of a two-level quantum emitter around a plasmonic nanorod

Spontaneous emission lifetime orientation distributions of a two-level quantum emitter in metallic nanorod structures are theoretically investigated by the rigorous electromagnetic Green function method. It was found that spontaneous emission lifetime strongly depended on the transition dipole orientation and the position of the emitter. The anisotropic factor defined as the ratio between the maximum and minimum values of the lifetimes along different dipole orientations can reach up to 103. It is much larger than those in dielectric structures which are only several times usually. Our results show that the localized plasmonic resonance effect provides a new degree of freedom to effectively control spontaneous emission by the dipole orientation of the quantum emitters.PACS: 78.67.Qa; 73.20.Mf; 42.50.-p

Diffractive properties of imaginary-part photonic crystal slab

The diffraction spectra of imaginary-part photonic crystal (IPPC) slabs are analyzed using the scattering-matrix method. By investigating the thickness dependence of the diffraction, we find a remarkable red shift of central wavelength of the diffraction spectrum, which obviously distinguishes from the phenomenon of spectral hole. We observe that diffraction efficiency can be enhanced more than 20-fold by optimizing the geometry parameters. These imply that the diffraction spectra of the IPPC slab can be controlled at will and used to guide the design to achieve useful nanoscale devices.