用扫描近场光学显微镜对凋亡的HeLa细胞进行了近场光学成像,得到优于光学衍射极限的光学分辨率.由于近场光学显微镜同时测量细胞表面形貌信息和透射光强信息,可以将细胞表面及其内部的物质结构特性和光学特性与空间位置相结合,获得凋亡细胞的结构信息与光学细节信息的对应关系.运用近场光谱方法在不同波长进行透射光谱成像时,不同波长的光在细胞内的传播与吸收所造成的光强分布存在显著差别,这种特性可以用于对细胞内不同组分的超高空间分辨率成像.结合近场光学成像和光谱成像结果,表明凋亡HeLa细胞内部为非均匀结构,并且其物质分布也极不均匀.研究表明,运用近场光学显微镜和近场光谱成像技术,不但提供优于衍射极限的高分辨本领,还可以提供生物细胞精细结构的更深层次的光学信息.

By using scanning near-field optical microscopy (SNOM), HeLa cells in apoptosis process are imaged with a higher optical resolution beyond the diffraction limit. Since SNOM provides both topographic and transmitted light intensity information of a cell, it can correlate the structural characteristics and optical properties with the spatial position of the apoptotic cells. Wavelength imaging by using near-field spectroscopy shows that there is a great difference in light propagation and absorption in the cell. This unique technique can be applied to the super high resolution imaging of different components in the cell. The observations by near-field optical imaging and near-field spectroscopy indicate an inhomogeneous aggregation of the inner structure in the apoptotic HeLa cells and the change of transmission intensity of light with the apoptosis status.

A thin film of GaN with the thickness of 1.0 µm was grown on α-Al2O3 substrate by metal organic chemical vapour disposition and then a thick GaN film with thickness of 12 µm was grown in the halide vapour phase epitaxy system. Some macro-pyramids appeared on the surface of the sample. The macro-pyramids made the surface of the GaN film rough, which was harmful to the devices made by GaN materials. These defects changed the distribution of carrier concentration and affected the optical properties of GaN. The step height of the pyramids was about 30-40 nm measured by atomic force microscopy. A simple model was proposed to explain the macro-pyramid phenomenon compared with the growth spiral. The growth of the macro-pyramid was relative to the physical conditions in the reaction zone. Both increasing growth temperature and low pressure may reduce the pyramid size.

Submicron ferromagnets have been successfully incorporated into the semi-insulating (001) GaAs crystals by Mn+ ion implantation and subsequently rapid annealing. Magnetization measurements reveal the room-temperature ferromagnetism. The structural and compositional properties of crystallites have been analyzed by transmission electron microscopy, energy dispersive X-ray spectroscopy and electron diffraction. The results show that crystallites of MnGa and MnAs with a small amount of Ga are formed. Images under the atomic force microscopy and magnetic force microscopy indicate that the single-domain magnetic state is dominant in submicron ferromagnets under our annealing conditions (750-900°C).

Using YBa2Cu3O7 (YBCO) as a buffer layer high T-c superconducting HgBa2CaCu2Oy (Hg-1212) thin films with zero resistance temperature (T-c) of 115-124 K and critical current density (J(c)) of 1 MA cm(-2) at 77 K in zero magnetic field have been grown on (100)Y-ZrO2 substrates. The high T-c, J(c) and good morphology indicate that YBCO is a good buffer for growing the Hg cuprate films. This novel buffer makes it possible to grow Hg cuprate films on many substrates, including some metallic tapes.

Submicron ferromagnets have been successfully incorporated into semi-insulating (001) GaAs crystals by Mn+ ion implantation and subsequent rapid annealing. Magnetization measurements reveal room-temperature ferromagnetism. The structural and compositional properties of crystallites have been analyzed by transmission electron microscopy, energy dispersion x-ray spectrum, and electron microdiffraction. The results show that crystallites of MnGa and MnAs with a small amount of Ga are formed. Atomic force microscopy and magnetic force microscopy images indicate that the single-domain magnetic state is dominant in submicron ferromagnets under our annealing conditions (750 °C–900 °C).

To overcome the isotropic directional emission of an ideal circular microdisk, two kinds of cylindrical mesa-like InGaAlP single quantum well (SQW) microdisks emitting at a visible red wavelength of 0.66 μm have been fabricated. An anisotropic luminescence pattern was revealed by the microscopic fluorescence (FL) image. FL intensity, preferentially enhanced with twofold symmetry, appeared at the circumference of the InGaAlP SQW microdisks. Our results demonstrated that anisotropic radiation can be achieved by geometry shaping of the disks on the top view two-dimensional boundary slightly deformed from circular shape and/or on the side-view cross-section of the circular mesa by wet etching anisotropic undercut.

We have constructed a versatile low temperature scanning near-field optical microscope with the capability of near-field spectroscopy, operating at liquid nitrogen (LN) temperature. The compact low temperature scanning head was built on one piece of Marco with a unique linear nano-motor as the coarse approach. A tuning fork mechanism was adopted to detect and regulate the fiber tip-sample separation. The x-y scan can be performed either by the single tube scanner or triple tube scanner, depending on the application. A double shield dewar was used where the outer chamber was filled with LN. The core chamber was evacuated before cooling and then filled with cooled nitrogen gas, hence the working temperature can be controlled at around 80K. A special designed coaxial double lens was used to introduce the illumination beam through a 200-micron fiber; the detected optical signal was transmitted via a fiber tip to a PMT or an APD. The performance test shows the stability of the new design. The resolution of shear force imaging and optical image of standard sample are shown.

Microcavity shows the growing importance of the intensity enhancement, inhibition and spectral narrowing of spontaneous emission. The advantages of microcavity lasers are the very low threshold and small size. We have fabricated three types of semiconductor microdisks: InGaP, GaN, and InGaN multi-quantum-well microdisk with sun-like E- beam resist microstructure. The diameters are ranging from 5 - 20 micros. The photoluminescence of those microdisks in far-field and near-field observation are compared. Far-field fluorescence imaging shows bright emission of fluorescence around the circumference of the microdisks that can be interpreted as whispering-gallery mode in the disks. However, due to the different disk structures, near-field fluorescence images give several other different views of the light distribution of the microdisks corresponding to different optical modes in the disks. A theoretical calculation of the light distribution of InGaP microdisk based on the theory of optical modes in microdisk lasers is presented in this paper. The near-field mapping of the InGaN microdisks with sun-like E-beam resist structure demonstrates the possibility of using gratings made on the circumference to achieve directional emission without lowering output power.