Proc. SPIE. 7658, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Detector, Imager, Display, and Energy Conversion Technology
KEYWORDS: Optical fibers, Diffraction, Refractive index, Super resolution, Nano opto mechanical systems, Reflectivity, Image resolution, Near field scanning optical microscopy, Near field, Near field optics
It is a review about the industrialization of Nano-Optical Microscope (NOM, also referred to as the Near-field Optical
Microscope). Two comparisons of AF/PSTM (Transmission Mode) with the first generation commercial A-SNOM and
AF/RNOM(Reflective Mode) with A-RNOM have discussed. The commercially used A-SNOM can only obtain a
transmissivity image of A-SNOM-T(<i>x,y</i>), but AF/PSTM can obtain the separating the transmissivity image PSTM-T(<i>x,y</i>)
and the refractive index imge PSTM-n<sub>1</sub>(<i>x,y</i>). AF/RNOM can obtain the lower contrast reflective index image but ARNOM
cannot. The reason how could Pohl have obtained the first A-SNOM image with a resolution of 20-25nm in
1984 but the commercial A-SNOM-T(<i>x,y</i>) only with the resolution in the 50~100nm range is also discussed. Conclusion
on the proposal of AF/PSTM and combined AF/RNOM may be the best candidate for the second generation commercial
use of NOM.
In this report, based on the near-field Raman theory which mechanism is fundamental different with the far-field Raman, a new viewpoint of near-field Raman was brought out. In this view, to be the excitation light, the effect of evanescent light in near-field Raman was emphasized, at same time, the evanescent light component in the Raman scattering light was noticed, too. The sample could be excited through evanescent light and the component of evanescent light in Raman scattering light was collected entirely in the novel ultra-sensitive near-field Raman sample cell. According to the sample cell, initial experiment was performed. The high aperture oil immersed object lens was employed to form excitation light which included evanescent light component. High signal-to-noise surface enhanced Raman scattering (SERS) signal of rat serum was obtained. By analysing the Raman spectrum, it was found that the new Raman peaks come out because of the excitation light including evanescent light.
We have developed an Atomic Force / Photon Scanning Tunneling Microscope (AF/PSTM) to eliminate the optical false image caused by topography of sample in PSTM. The key element of this system is bi-functional bent optical fiber probe, which can both be an optical cantilever and a device to collect the evanescent wave in near field of samples. In this paper, we derived a method to fabricate the bi-functional bent optical probes of AF/PSTM using communication optical fibers. The heated pulling combined with chemical etching method is proposed and developed. Fiber probes with an apex having a diameter smaller than 100nm could be produced with a controlled cone angles vary from 40 to 90 degrees. The back of the probe is finally coated with aluminum to enhance the reflection and with SiO<sub>2</sub> to prevent Al film from oxidating in the atmosphere. This method is straightforward and fast. Using probes made with this method, the images of biology samples are obtained and the image separation is realized.
Photon Scanning Tunneling Microscope (PSTM) is a near-field optical microscope that can measure local optical properties with high resolution beyond the diffraction limit and was widely applied in practices in recent years. The resolution of PSTM, which mainly depends on the shape of the taper tip, is an important issue to be discussed in the application. In this paper, the near-field distribution around a new PSTM probe is simulated by the method of 3-D Finite-Difference Time-Domain (FDTD). In this model, a nanometric metallic pyramid is attached at the apex of the metal-coated probe. Considering the interaction between the sample and the probe tip, the near-field distribution in a section at certain height is plotted as a function of the various sample positions. In order to optimize the optical property of this kind of optic fiber probe tip, the influence of the parameters of the taper tip can also be studied. To understand the effect of the probe film and the metal tip, the electromagnetic field distribution in the vicinities of the sample and the fiber probe during the third period is plotted. Thus, these simulated results offer references for the selection of the probe shape in experiments.
The combination of plasmon near-field scanning optical microscopy (PNSOM) and Raman spectroscopy named Near-field Scanning Raman Microscopy (SNRM) provides not only surface topography information but also chemical structural information of sample with nanometer spatial resolution, which are very important for a wide range of applications, such as the study of liquid sample, nanometer film sample, quantum dot, single molecules of biological samples and so on. But Raman scattering cross-section is too small to get Raman signal of nanometer structure, and surface enhancement Raman scattering (SERS) effect is the main technique to solve this problem. Local electric field distribution and the form of the hot spots are evaluated by the FDTD (finite difference time domain) method in SERS with respect to many kinds of models. As a result in this paper, (1) vast Raman enhancement factor of 10<sup>15</sup> was obtained around the junction between the Ag ball (tip) and the Ag thin film (sample stage). (2) The enormous large electric field at the hot spots rapidly decays with increasing gap between the Ag ball and Ag thin film. In the process, we use the equivalent incident wave method to deal with the incident evanescent wave problem and a frequency-dependent finite-difference time-domain formulation ((FD)<sup>2</sup> TD) to deal with the negative permittivity of Ag, and the validity of these two methods have been approved by references
In this paper, three types of simulations will be performed using the three-dimensional finite difference time domain (3D-FDTD) method. First, we simulate the visualized interaction procedure of evanescent field coupling to the PSTM probe tip. Then, we show the variation in the field distribution above the sample as its refractive index and thickness are increased. Finally, we simulate the refractive index images based on the principle of separation of the refractive index image from the images of AF/PSTM for the realistic experiments. The numerical results are in good coincidence with the experimental results.
Proc. SPIE. 5630, Optics in Health Care and Biomedical Optics: Diagnostics and Treatment II
KEYWORDS: Nanostructures, Refractive index, Biomedical optics, Statistical analysis, Atomic force microscopy, Biology, Near field scanning optical microscopy, Biological research, Scanning probe microscopy, Near field optics
As an analysis tool, SPM has been broadly used in biomedicine in recent years, such as AFM and SNOM; they are effective instruments in detecting life nanostructures at atomic level. Atomic force and photon scanning tunneling microscope (AF/PSTM) is one of member of SPM, it can be used to obtain sample’ optical and atomic fore images at once scanning, these images include the transmissivity image, reflection index image and topography image. This report mainly introduces the application of AF/PSTM in red blood membrane and the effect of different sample dealt with processes on the experiment result. The materials for preparing red cells membrane samples are anticoagulant blood, isotonic phosphatic buffer solution (PBS) and new two times distilled water. The images of AF/PSTM give real expression to the biology samples’ fact despite of different sample dealt with processes, which prove that AF/PSTM suits to biology sample imaging. At the same time, the optical images and the topography image of AF/PSTM of the same sample are complementary with each other; this will make AF/PSTM a facile tool to analysis biologic samples’ nanostructure. As another sample, this paper gives the application of AF/PSTM in immunoassay, the result shows that AF/PSTM is suit to analysis biologic sample, and it will become a new tool for biomedicine test.
Our research group has recently developed a new type scanning probe microscope —AF/ PSTM. Using this setup, the optical false image caused by the inclination of sample surface can be eliminated; the optical image and the topography image are separated; and also two optical images (refractive index image, transmittivity image) and two AFM images (topography image, phase image) are obtained during one scanning. As a primary biologic application, this setup is engaged in the imaging of some biologic samples. The primary images ofthese biologic samples are obtained. Due to the advantage of AFIPSTM, four images can be acquired at the same time during one scanning. Consequently more information ofsample is given by comparing these images. This work shows that the AF/PSTM may be improved to be a useful tool in biology research.
It is important to analyze the images obtained by photon scanning tunneling microscope (PSTM). Recently some theories have been developed including finite-difference time-domain (FDTD) method applied in near field optics. In this article wc extend a simple FDTD method (equivalent incident wave method) to PSTM system, which has been widely used to detect objects buried underground in geophysics. In PSTM system lighting wave is evanescent wave, that is the equivalent incident wave exciting the samples and probe over the interface. Numerical simulations show that the results ofthis method are in agreement with the results ofthe moment method and perturbation theory.
KEYWORDS: Refractive index, Patents, Magnesium fluoride, Glasses, Photography, Atomic force microscopy, Near field scanning optical microscopy, Scanning tunneling microscopy, Photonic microstructures, Near field optics
According to author's Chinese invented patent ZL96 I II 979.9 named "The method of separating image of AF/PSTM (atom force and photon scanning tunneling microscope)", the first system ofAF/PSTM has been developed. Its principle, photograph, block diagram and some images ofan examination sample have been given in this paper. There are three advantages of this system: (1) AF/PSTM can eliminate the optical false image which caused by topography of sample in PSTM; (2) The optical images and topographic image of sample are separated with this AF/PSTM; (3) From once scanning imaging two optical images (refractive index image and transmissivity image) and two AFM images (topography image and phase or grads oftopography image) can be obtained.
Photon Scanning Tunneling Microscope (PSTM) is a newly developed technique. As a near-field optical microscope, it has the high resolution breaking through the diffraction limit and the advantage for easy to prepare the samples. PSTM is a useful tool in the inspection for many kinds of material film as the image containing the sample's information of topography and refractive index. We have developed a PSTM with resolution 5 to approximately 10 nm and scanning range 6 X 6 micrometer. By making use of two lasers, the false image caused by inclination of sample surface can be reduced. This PSTM is engaged in the inspection of Al<SUB>2</SUB>O<SUB>3</SUB> optical waveguide film made using ion-beam-enhanced-deposition (IBED) technique at different substrate temperature. The PSTM images of the optical waveguide film are obtained and analyzed. The PSTM images show that as the increasing of the substrate temperature during the deposition, the sample images of refractive index and topography tend to smooth and even, consequently the scattering loss can be decreased. The conclusion is that by properly increasing the temperature of the substrate during the deposition period, the scattering loss can be decreased and the property of Al<SUB>2</SUB>O<SUB>3</SUB> optical waveguide can be improved.
Proc. SPIE. 3467, Far- and Near-Field Optics: Physics and Information Processing
KEYWORDS: Diffraction, Refractive index, Super resolution, Optical microscopy, Numerical simulations, Near field scanning optical microscopy, Light sources and illumination, Scanning tunneling microscopy, Photonic microstructures, Near field optics
This paper attempts to answer the question of 'how to explain the image of photon scanning tunneling microscope (PSTM)'. To explain the image of PSTM, the essential difficulty is the false image information within the complex image of the topographical image and refractive index image of sample. In this paper, we have derived the PSTM imaging formula and introduced the eliminating false image information method and image separating method, and discussed the key to super-resolution of near-field optical microscopy. Numerical simulation and experiments with the method of perturbation diffraction combined with (pi) - symmetric lighting eliminating false image information are provided.
In 1991, American Patent Bureau Published the Patent of Photon Scanning Tunnel- ing Microscopy CUSP 5,018,865). Now we name that instrument 1st generation PSTM. Our group obtained first PSTM image of a holographic grating with resolution of 100nm october 1991, and super-resolution images with lateral beter than 10nm and longitude bet- ter than 1nm, using the 1st generation PSTM in 1993.