Patrick J. Moyer

Resolution in collection‐mode scanning optical microscopy

The use of small apertures or sharpened tips as sensing elements in scanned‐probe optical sensing devices has led to the development of a number of instruments that provide lateral spatial resolution much finer than that available in conventional optical imaging instruments. Such a device might generally be classified as a scanning optical microscope, or SOM. One particular mode of SOM operation involves the use of a sharpened optical fiber to collect light emanating from a surface. The lateral spatial resolution of such a collection‐mode SOM is discussed in terms of the electromagnetic mode solutions of the probe tip. Numerical results indicate that, though bound modes solutions exist for increasingly fine unclad tips, classical diffraction effects limit resolution to a finite fraction (approximately 1/3) of the source wavelength λ. A second mechanism for signal transduction is shown to involve molecular scattering at the probe tip. An analysis of signal collection efficiency demonstrates that at tip rad...

Kinetic limits for sensing tip morphology in near‐field scanning optical microscopes

The lateral spatial resolution provided by near‐field scanning optical microscopes depends critically on the shape and size of the sharpened tip of the optical fiber used as a source of light or sensing element. The fabrication of a tip by the commonly used heating and pulling method is examined. It consists of an initially pulling and rupture followed by a cooling and relaxation. The presented analysis leads to a deeper physical understanding of these processes and suggests avenues for technical improvements.

Shear force/reflection near-field scanning optical microscopy

The spatial resolution afforded by near-field scanning optical microscopy (NSOM) is primarily a function of tip size and tip-sample separation. Combining scanning force microscopy with NSOM allows one to maintain a small tip-sample separation distance and, consequently, optimize NSOM resolution. This provides, simultaneously, a topographic perspective of the sample as well as an NSOM image. We present, in this paper, an instrument that provides simultaneous shear force and reflection NSOM images. We also incorporate a tip deflection detection scheme that allows the force signal to be completely decoupled from the optical signal. In order to accurately analyze the NSOM images, it is important to understand the feedback mechanism so that proper image deconvolution can be performed. Considerations concerning the forces measured are made. A discussion concerning Raman scattering capabilities in this regime is also provided, along with some preliminary Raman data.

Resolution issues in scanning optical microscopies

Several issues concerning lateral spatial resolution in scanning optical microscopes, SOMs, are addressed. After identifying what is meant by resolution in an SOM, the role of probe tip morphology is discussed. Consideration of the physical mechanism of signal transduction is made, and fundamental differences between near field SOMs and evanescent field SOMs are underscored. Therole of dithering of the probe tip in improving resolution is demonstrated and discussed.

Applications of spin-on-glass for waveguide and micro-optical systems

We have developed a material system, a fabrication process, and optical designs that allow for direct integration of patternable optical components onto microelectronics and optoelectronics platforms. The spin-on-glass is a sol-gel platform that has a low waveguide loss with the ability to incorporate a waveguide amplifier. Our material and process includes the ability to fabricate 3-D structures in a single photolithography step. In this paper, we present details of our fabrication process, general materials characteristics, and some optical designs for planar lightwave circuit platforms.