Scanning probe optical microscope using a solid immersion lens

A optical microscope comprising

• a) an objective lens;
• b) a beamsplitter above the objective lens, such that light for illuminating a sample may be directed from a source of illumination to the objective lens, and that a portion of the light emerging from the objective lens may be directed to light detection apparatus;
• c) a solid immersion lens below the objective lens, said solid immersion lens having an upper surface and a lower surface, with said lower surface forming a probe tip, such that light from the objective lens is focused at the probe tip;
• and
• d) a vertical positioner for controlling the distance of the probe tip on the solid immersion lens from a sample;
• whereby light from a source of illumination may be directed to a small spot on a sample, and the optical characteristics of a small area of sample may be determined.

A scanning probe optical microscope comprising

• a) a sample support;
• b) a solid immersion lens of a high index of refraction material, said solid immersion lens having a first surface and a second surface, with said second surface forming a probe tip;
• the high index of refraction of the material establishing a critical angle, such that
• 1) a light ray within the material and incident to a surface at an angle less than the critical angle is reflected and refracted at the surface, and
• 2) a light ray within the material and incident to a surface at an angle greater than the critical angle is totally internally reflected to produce a reflected ray and an evanescent wave;
• c) optical means for focusing light through the first surface of the solid immersion lens to a focal spot at the probe tip on the second surface of the solid immersion lens;
• d) a vertical positioner for controlling the distance of the probe tip on the solid immersion lens relative to the sample;
• e) a scanner for translating the solid immersion lens and the sample support relative to one another along a substantially horizontal plane;
• and
• f) optical means for collecting light from the sample;
• whereby the optical characteristics of translucent samples may be determined with a resolution better than the diffraction limit in air.

A combined scanning probe optical microscope and atomic force microscope, comprising

• a) a cantilever having a base end and a distal end, said distal end equipped with a solid immersion lens having an upper surface and a lower surface, said lower surface forming an atomic force microscope probe tip;
• b) the solid immersion lens being formed of a high index of refraction material, the high index of refraction of the material establishing a critical angle, such that
• 1) a light ray within the material and incident to a surface at an angle less than the critical angle is reflected and refracted at the surface, and
• 2) a light ray within the material and incident to a surface at an angle greater than the critical angle is totally internally reflected to produce a reflected ray and an evanescent wave;
• c) a position control mechanism for controlling the position of a sample with respect to the base end of the cantilever;
• d) a small-displacement measuring mechanism for measuring a deflection amount of the cantilever;
• e) a feedback control mechanism for fine control of the vertical position of the probe tip having as one input the deflection amount of the cantilever;
• f) means for recording vertical and horizontal position data of the probe tip;
• g) optical means for focusing light through the first surface of the solid immersion lens to a focal spot at the probe tip on the second surface of the solid immersion lens, such that some light within the solid immersion lens impinges on the probe tip at an angle greater than the critical angle, creating an evanescent field adjacent to the probe tip;
• and
• h) optical means for collecting the light emerging from the upper surface of the solid immersion lens;
• whereby both atomic force and near-field optical information may be obtained about both smooth and rough samples, with the optical data providing a resolution better than the diffraction limit in air.

A combined scanning probe optical microscope and atomic force microscope, comprising

• a) a cantilever having a base end and a distal end, said distal end equipped with a solid immersion lens having an upper surface and a lower surface, said lower surface forming an atomic force microscope probe tip;
• b) the solid immersion lens being formed of a high index of refraction material, the high index of refraction of the material establishing a critical angle, such that
• 1) a light ray within the material and incident to a surface at an angle less than the critical angle is reflected and refracted at the surface, and
• 2) a light ray within the material and incident to a surface at an angle greater than the critical angle is totally internally reflected to produce a reflected ray and an evanescent wave;
• c) a position control mechanism for controlling the position of a sample with respect to the base end of the cantilever;
• d) a small-displacement measuring mechanism for measuring a deflection amount of the cantilever;
• e) a feedback control mechanism for fine control of the vertical position of the probe tip having as one input the deflection amount of the cantilever;
• f) means for recording vertical and horizontal position data of the probe tip;
• g) optical means for focusing light through the first surface of the solid immersion lens to a focal spot at the probe tip on the second surface of the solid immersion lens, such that some light within the solid immersion lens impinges on the probe tip at an angle greater than the critical angle, creating an evanescent field adjacent to the probe tip;
• and
• h) optical means for collecting the light transmitted from the probe tip through a translucent sample;
• whereby both atomic force and near-field optical information may be obtained about both smooth and rough translucent samples, with the optical data providing a resolution better than the diffraction limit in air.

A method of illuminating a small spot on a smooth or rough sample comprising

• a) positioning a solid immersion lens of a high index of refraction material having a first surface and second surface, said second surface forming a probe tip, within the near-field of a surface to be illuminated;
• the solid immersion lens being formed of a high index of refraction material, the high index of refraction of the material establishing a critical angle, such that
• 1) a light ray within the material and incident to a surface at an angle less than the critical angle is reflected and refracted at the surface, and
• 2) a light ray within the material and incident to a surface at an angle greater than the critical angle is totally internally reflected to produce a reflected ray and an evanescent wave;
• b) focusing light through the first surface of the solid immersion lens to a focal spot at the probe tip on the second surface of the solid immersion lens, such that some light within the solid immersion lens impinges on the probe tip at an angle greater than the critical angle, creating an evanescent field adjacent to the probe tip,
• whereby the sample near the tip is efficiently illuminated by the evanescent field at the probe tip.

A method of measuring the optical characteristics of a small spot on a smooth or rough sample comprising

• a) positioning a solid immersion lens of a high index of refraction material having a first surface and second surface, said second surface forming a probe tip, within the near-field of a surface to be illuminated;
• the solid immersion lens being formed of a high index of refraction material, the high index of refraction of the material establishing a critical angle, such that
• 1) a light ray within the material and incident to a surface at an angle less than the critical angle is reflected and refracted at the surface, and
• 2) a light ray within the material and incident to a surface at an angle greater than the critical angle is totally internally reflected to produce a reflected ray and an evanescent wave;
• b) focusing light through the first surface of the solid immersion lens to a focal spot at the probe tip on the second surface of the solid immersion lens, such that some light within the solid immersion lens impinges on the probe tip at an angle greater than the critical angle, creating an evanescent field adjacent to the probe tip;
• c) collecting the light emerging from the upper surface of the solid immersion lens;
• d) measuring characteristics of the collected light,
• whereby the sample near the tip is efficiently illuminated by the evanescent field at the probe tip, and light is efficiently collected from the probe tip for measurement and analysis.

A method of optical microscopy of a smooth or rough sample, comprising

• a) positioning a solid immersion lens of a high index of refraction material having a first surface and second surface, said second surface forming a probe tip, within the near-field of a surface to be illuminated;
• the solid immersion lens being formed of a high index of refraction material, the high index of refraction of the material establishing a critical angle, such that
• 1) a light ray within the material and incident to a surface at an angle less than the critical angle is reflected and refracted at the surface, and
• 2) a light ray within the material and incident to a surface at an angle greater than the critical angle is totally internally reflected to produce a reflected ray and an evanescent wave;
• b) focusing light through the first surface of the solid immersion lens to a focal spot at the probe tip on the second surface of the solid immersion lens, such that some light within the solid immersion lens impinges on the probe tip at an angle greater than the critical angle, creating an evanescent field adjacent to the probe tip;
• c) collecting the light emerging from the upper surface of the solid immersion lens;
• d) measuring of the collected light;
• e) repeating steps a) through d) as the probe is scanned over the surface;
• and
• f) analyzing and assembling the collected data into an optical image,
• whereby the sample near the tip is efficiently illuminated by the evanescent field at the probe tip, light is efficiently collected from the probe tip for measurement;
• and optical images of both smooth and rough samples at a resolution better than the diffraction limit in air may be obtained.

A method of combined atomic force and optical microscopy of a smooth or rough sample, comprising

• a) performing an atomic force microscope (AFM) scan of a sample using a solid immersion lens of a high index of refraction material as an AFM probe, said solid immersion lens having a first surface and second surface, said second surface forming a probe tip;
• the solid immersion lens being formed of a high index of refraction material, the high index of refraction of the material establishing a critical angle, such that
• 1 ) a light ray within the material and incident to a surface at an angle less than the critical angle is reflected and refracted at the surface, and
• 2) a light ray within the material and incident to a surface at an angle greater than the critical angle is totally internally reflected to produce a reflected ray and an evanescent wave;
• b) storing the atomic force microscope scan information in a memory device, said scan information including height data Z corresponding to each X and Y location of the scan;
• c) calculating from the stored scan data a new height value Z' for each X and Y location of the scan, the new height value being a constant distance above the sample, and within the evanescent field of the sample;
• d) repositioning the probe on the second surface of the solid immersion lens to an X and Y location of the AFM scan, at the new height value Z';
• e) focusing light through the first surface of the solid immersion lens to a focal spot at the probe tip on the second surface of the solid immersion lens, such that some light within the solid immersion lens impinges on the probe tip at an angle greater than the critical angle, creating an evanescent field adjacent to the probe tip;
• f) collecting the light emerging from the upper surface of the solid immersion lens;
• g) measuring characteristics of the collected light;
• h) repeating steps d) through g) for each X and Y location of the scan;
• and
• i) analyzing and assembling the collected data into an optical image,
• whereby the sample near the tip is efficiently illuminated by the evanescent field at the probe tip, light is efficiently collected from the probe tip for measurement;
• optical images of smooth or rough samples at a resolution better than the diffraction limit in air may be obtained;
• and the optical characteristics of the sample may be distinguished from the effects of probe-to-sample distance.