We present a new scheme of atom manipulation by means of a sharpened optical fiber with near-field light. In particular, we discuss the feasibility of deflecting and trapping Rb atoms. The optical potential produced by the dipole force is estimated from numerical calculations based on the Yukawa-type intensity distribution. We show that a slow Rb atom can be deflected at a large deflection angle. A static atom trap can be made near the tip of a sharpened fiber. A cold Rb atom is captured at the minimum of the trap potential composed of the repulsive optical potential and the attractive van der Waals potential. A spatial intensity distribution of an optical near-field produced near the tip of a protrusion-type fiber is measured in the fiber-to-probe configuration with a shear-force technique. We also describe an atom funnel to form a cold atomic beam required for the near-field light manipulation.

We point out that recent experimental results exemplify the need for quantum theoretical treatment of optical near-field problems, as well as the need for an intuitive model that provides clear insights into near-field optical systems. In this context, the virtual photon model as an intuitive model is discussed, and a quantum theoretical formulation of an optical near-field system is proposed on the basis of the projection-operator method. Special attention is paid to nanometric probe tip and quantum-mechanical sample systems such as atoms, molecules, and quantum dots. The effective probe tip-sample interaction is derived from the microscopic viewpoint; this interaction is essential for describing such phenomena as atom guidance and manipulation, or local excitation of a single quantum dot. The relationship to the virtual photon model is also discussed by focusing on the latter's empirical assumption of Yukawa-type interaction between the probe tip and sample. The key points are that a probe tip exists near the sample, and that the electron energies in the probe tip or sample are inversely proportional to the square of its size, owing to the confinement effect. Several applications and the future prospects of our theory are also briefly outlined.

We have developed an integrated micro-probe with improved detection efficiency for apertureless near-field scanning optical microscopy (NSOM) by using micromachining techniques; we call this probe a `photocantilever'. A photocantilever is an integrated micro-cantilever with a pn- junction at its end; it is fabricated using micromachining techniques. It has achieve higher collection efficiency than conventional NSOM probes because the detector is placed close to the scatterer. Two new types of NSOM can be performed using this photocantilever: totally-internal- reflection-illumination-based NSOM and differential NSOM. Both provide NSOMs with high spatial resolution. The photocantilever enables apertureless NSOM with high collection efficiency and high resolution.

We discuss some of the intrinsic difficulties related to the numerical investigation of near-field optical microscopy. We show how these difficulties can be handled within the framework of the Green's tensor technique. Investigating practical experimental configurations, we show the strong correlation between the motion of the tip and the near-field signal. In order to investigate this kind of artifacts, we propose a series of experiments based on photonic band gap systems immersed in evanescent fields. The electromagnetic properties of such a system can be changed without changing the topography of the system at all.

We have developed a NSOM which has a metallic probe tip and a highly focused evanescent light field spot. Evanescent illumination effectively rejects the background light, e.g. the stray light from the shaft of the probe. By suppressing the stray light and utilizing the field enhancement generated by the metallic probe, a sudden increment of the fluorescence was observed in the near-field region. We have used this for near-field Raman scattering detection of molecules vibrations with the aid of surface enhanced Raman scattering. One specific stokes-Raman-shifted lines was observed by near-field excitation together with several other lines that were excited by the far-field light.

We describe experiments demonstrating the performance of a recently developed combined near-field and confocal polarization microscope, which was designed for imaging microstructure in soft anisotropic polymer films. Phase modulation (PM) of light (488 nm) is implemented in both near-field and confocal channels to increase sensitivity to birefringence. Images of radially symmetric objects, spherulites, in the polyethylene films confirmed the high performance of this microscope in imaging of both magnitude and sign of birefringence. On the other hand, PM images of the crosslinked polybutadiene films revealed unexpected domain structure that indicates heterogeneity in local chain deformations and alignments. It is shown that the domains are correlated with the local density fluctuations of crosslinks.

A simple novel probe for Scanning Near-field Optical Microscope (SNOM) is proposed. The probe consists of a small protrusion on a micro resonator. The resonator and protrusion is a spherical micro sphere with diameter of 50-70 μm, 1.5 μm, respectively. The resonator is a polystyrene latex sphere and the protrusion is a polymethyl methacrylate sphere. The s-polarized laser (Ti:Sapphire laser) beam, which illuminates the resonator through an evanescent wave, can be tuned to the resonant frequencies. The resonance occurred in the sphere is a traveling wave resonance, which is called MDRs (Morphology Dependent Resonances) or WGMs (Whispering Gallery Modes). The internal resonant wave could generate an intensive evanescent field on the surface of the resonator. The small protrusion on the resonator combines with the evanescent field and could acts as a high sensitive probe for SNOM. A clear image of the protrusion illuminated by the evanescent field on the resonator was observed with the cooled CCD detector. The brightness of the image of the protrusion depends on the laser wavelength. The optical characteristics of the resonant probe is also studied by a Finite-Difference Time- Domain method.

We applied a super-wavelength apertured fiber probe to phase-change recording/readout. Though the fiber probe had a super-wavelength aperture, the spot size at the aperture was as small as 150 nm (< λ/5). An as-deposited SiO₂/AgInTe₂/glass substrate was used as a recording medium. For recording, a laser diode with a pulsewidth of 2 μs (λ=850 nm) was used. By scanning the probe for reading, we obtained resolved images of the recorded dot with a width of 250 nm.

We propose and demonstrate a new optical near-field slider with a planar apertured probe array for optical memory. The slider was fabricated by utilizing anisotropical etching of a silicon membrane and anodic bonding of a silicon membrane and glass substrate. We also present for the first time a subwavelength-sized phase-change recording/reading by using the planar apertured probe array. Apertures were fabricated at the bottom end of the pyramidal grooves. A SiO₂/AgInTe₂/glass substrate was used as the recording medium. By scanning the planar apertured probe array, we obtained resolved images with line width of 250 nm.

Thin films of randomly distributed silver nanoparticles are studied experimentally using photon scanning tunneling microscopy and theoretically using real-space renormalization group method. The studies reveal large variations of local optical intensity at sub-wavelength scales. In addition, irradiation of the film by nanosecond laser pulses is observed to yield substantial changes in the local optical response. The threshold for the photomodification is less than 10 mJ/cm². It is believed that particles within some areas of nanometer scales are restructured during nanosecond laser irradiation. The geometric changes in turn result in modification of the local optical intensity.

The original concept of photonic crystals (PCs) was introduced in 1987 by Yablonovitch and John. Since then, there has been a great deal of interest in this field. Extensive research has been reported on the physical concepts, device fabrications, and a wide range of applications. Recent advances in materials engineering and nanofabrication technologies have led to new successful practical realizations of different types of PC structures. In this paper, the concepts, fabrication techniques, devices and applications, and measurement and characterization techniques are reviewed. In addition, future directions in research and development are briefly discussed.

Near-field spectroscopy of self-assembled InGaAs single quantum dots (QDs) is described. For the application of near-field optical microscope to various versions of advanced spectroscopy of single QDs, the functional performance of a near-field fiber probe is much improved. By optimizing the structure of this probe, high sensitivity in signal detection, as well as high spatial resolution, is successfully achieved. In combination with a standard pump- probe spectroscopic techniques, we realize nonlinear absorption spectroscopy of single QDs at low temperature. The absorption cross section of a single QD is effectively modified by local injection of a few electrons into the QD. Employing a femtosecond pulsed laser, time-resolved photoluminescence spectroscopy is also performed.

In-situ patterning of nano-scale Zn dots and lines has been succeeded by photodissociation of a gas-phase diethylzinc in optical near-field. By using an optical fiber probe with the aperture diameter of 60 nm, dots with full width at half maximum of approximately 60 nm and approximately 70 nm, closely separated by 100 nm were fabricated. It implies that finer patterns of a metal can be fabricated by using optical fiber probe with smaller aperture, allowing control of the size and position of nano-scale structures. Consequently, the technique is the one of most suitable for nano-photonic device fabrication.

ZnO nanodots have been successfully fabricated on a (001) Al₂O₃ substrate by photo-enhanced chemical vapor deposition (PE-MOCVD) combined with near-field optical technology. The optical near-field generated from an optical fiber probe tip allowed ZnO dots to selectively grow on the irradiated substrate surface, with a size smaller than the wavelength of the light source (λ=244 nm). The crystallinity and composition of ZnO were evaluated from planar films using x-ray diffraction analysis, optical transmittance and x-ray photoelectron spectroscopy. The planar films were grown using PE-MOCVD with a direct irradiation by an ultraviolet light source without probe tip. Above a deposition temperature of 150°C, stoichiometric ZnO films (R O:Zn=1), strongly the c-axis oriented and exhibiting a band gap of about 3.3 eV were obtained.

We have developed a nanometric fabrication system by manipulating chromium (Cr) atoms with laser beams. We utilized a laser diode with very narrow linewidth (approximately 5 MHz) to generate the photon force on the Cr atoms. The gradient force is exerted on the atoms in a standing wave, and the atoms are deposited in the periodical low potential regions of the standing wave, and a series of Cr lines are formed on the substrate with the periodicity of the standing wave. In order to optimize conditions for this deposition technique, we have performed a numerical analysis of the property of fabrication by tracing the trajectories of the atoms in the potential of light field. We found that the laser power and the degree of the collimation of the atom beam are important to obtain sharp structures. In addition, the longitudinal deceleration of the atom beam reduces strongly the structure size and increases the depth of the focus of the atom beam.

A new approach to simulation of light propagation through structures with nanometer-sized features is presented. The approach is based on the use of plane waves covering a wide range of spatial frequencies. The advantages of great numerical efficiency and some conception problems connected with the application of fast Fourier transform to a non- uniform medium are considered. Vector field representation and Maxwell's boundary conditions treatment are discussed. The simulation model is used to represent the light distribution passing through a tapered part of a scanning near-field optical probe.

We present a numerical comparison between shear-force, constant-height and constant-intensity images in scanning near-field optical microscopy. We demonstrate the general difference between the three images. Two type of incident light are tested of polarization in perpendicular and parallel direction with respect to the mean plane of the surface. Merits and demerits of the three images are discussed.

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.

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 on 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 80 K. 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.

Scanning near-field optical microscope (SNOM) can provide optical imaging with ultrahigh resolution owing to its breakthrough the limit of optical diffraction. Metal coated optical fiber probe in nano-scale is one of the most important parts in aperture type of SNOM. Tip diameter and structure determine the final spatial resolution and experimental utility of SNOM. In order to understand the behavior of light propagation in the probes, we have investigated two kinds of 3D probe models (metal coated and uncoated) by solving Maxwell equations with the Finite- Difference Time-Domain method. The 3D computation reveals that the field distribution of light in the probes are some patterns due to the polarization of light and the structure of the probe. This result can guide to find optimized tip design.