Ricardo Toledo-Crow

Near-field differential scanning optical microscope with atomic force regulation

We present the design and describe the operation of a scanning probe microscope which simultaneously provides the attractive mode force and near‐field optical images of objects. In this technique, the force signal is used to track the topography, thus allowing the optical signal primarily to show variations in transmissivity. A number of results are presented on the application of the technique to imaging different samples.

Phase contrast and amplitude pseudoheterodyne interference near field scanning optical microscopy

Pseudoheterodyne detection of sample light in near field optical microscopy is demonstrated in an actively stabilized Mach–Zehnder interferometer. This results in a significant signal enhancement. Three distinct imaging modalities are described, which are based on the various stabilization feedback parameters, and scan speeds. A number of images are presented, demonstrating both amplitude and phase contrast imaging modalities.

ON THE HEATING OF THE FIBER TIP IN A NEAR-FIELD SCANNING OPTICAL MICROSCOPE

Variation of the reflectance of the aluminized tip of a near‐field scanning optical microscope is used to measure the temperature rise due the confinement of light in the tip. The measurement technique involves a pump‐probe beam approach, and uses a two‐step process which eliminates the need to know the dependence of the signal on the scattering cross section of the tip.

Pure linear polarization imaging in near field scanning optical microscopy

The design and theory of operation of a new form of near field polarizing optical microscope are presented. The system uses electro‐optic premodulation of light to generate two simultaneous complementary images of samples. This affords the capability to obtain a final output signal which is a linear representation of the sample birefringence, and is independent of the sample transmissivity/reflectivity. A number of images are presented.

Contrast mechanisms and imaging modes in near field optical microscopy

Abstract The use of near field optical microscopy in a number of different circumstances is described, and various contrast mechanisms are explored. Results are presented on imaging polarization effects in tightly focused fields and magneto-optic media, and on correlative microscopy of porous silicon photoluminescence and topography.

Atomic-force-regulated near-field scanning optical microscope

The design and theory of operation of a new form of near field scanning optical microscope are presented. In this system, the tip/sample distance regulation is achieved in a feedback system utilizing the topography information derived from the attractive force sensed between the tip and the sample. The technique affords the possibility of correlative microscopy. Results are presented on imaging blood smears and thin film integrated circuits.

Near-field optical microscopy characterization of IC metrology

Images of a microlithographic sample obtained using a new near field scanning optical microscope (NSOM) that uses force regulation of the sample-tip separation are presented. The NSOM is a research instrument fitted with a metal covered glass tip probe that defines a small aperture at the sharp end. The aperture is estimated to be on the order of 100 nanometers in diameter resulting in a resolution exceeding that of diffraction limited systems. This form of microscopy can be done both in the transmission and the reflection modes. The force regulation mechanism produces a simultaneously obtained scanned force microscope image of the topography thus permitting correlative imaging of the sample. The samples are imaged in transmission and reflection near field optical format, with white light and with coherent light. The results are compared with other forms of IC imaging and characterization, namely scanned force microscopy and scanning electron microscopy.

Polarization, Interference Contrast, and Photoluminescence Imaging in Near Field Optical Microscopy

The design and operation of a number of techniques in near field optical microscopy are described. Specific attention is paid to the three modalities of polarization, interference contrast, and photoluminescence imaging. By premodulating the polarization state of the sample beam, pure, linear, polarizing microscopy is performed. In addition, polarization anomalies are observed in the focal plane of a high numerical aperture lens. Amplitude and phase contrast imaging is performed in a feedback stabilized Mach-Zehnder interferometer. Magneto-optically induced polarization shifts are detected interferometrically, resulting in linear sensitivity. Localized photoluminescence is induced in porous silicon, and the results are correlated with the topography of the sample.

Near-field microscopy of thin films: application to polymeric structures

Near field scanning optical microscopy of thin birefringent samples is described. The system utilized is the linear polarizing near field microscope, resulting in a pure birefringence image of the sample. The sign of the birefringence is also preserved. Two specific classes of sample are studied. These include thin sections of Kevlar fibers, and polymer dispersed liquid crystals. Results are correlated with simultaneously obtained topographic images. Based on experimental observations, the relative strength of the optical indices of the structures is determined

Imaging modes and contrast in near-field scanning optical microscopy

Near field scanning optical microscopy (NSOM) provides a number of unique capabilities for high resolution imaging. In this regard, a fundamental aspect of the technique is its ability to retain much of the characteristics available in diffraction limited optical probing. Results are presented on the use of near field scanning optical microscopy (NSOM) in imaging a variety of samples, using different contrast mechanisms. The approaches adopted are based on the recently introduced simultaneous, non-contact, near field optical microscope with atomic force regulation. Amongst the techniques discussed are linearized polarizing microscopy, as well as amplitude, and phase, interference contrast imaging modalities.