Scanning probe optical microscope using a solid immersion lens

• US 5,939,709 A
• Filed: 06/19/1997
• Issued: 08/17/1999
• Est. Priority Date: 06/19/1997
• Status: Expired due to Fees

• Current Assignee: Lucien P. Ghislain, Virgil B. Elings
• Original Assignee: Lucien P. Ghislain, Virgil B. Elings
• Inventors: Ghislain, Lucien P., Elings, Virgil B.
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): Lee, John R.
• Application Number:
  US08/878,987
• Time in Patent Office: 789 Days
• Field of Search: 250/216, 250/234, 250/306, 250/307, 250/235, 250/227.11, 250/492.2, 359/356, 359/389, 359/664, 359/824, 359/555, 359/368, 359/510, 359/514, 359/646, 359/661, 359/822, 359/823, 359/819, 359/382, 359/383, 359/391, 359/392
• US Class Current: 250/216
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: G01Q 60/22 Probes, their manufacture, or their related instrumentation, e.g. holders
• CPC Class Codes: G02B 21/02 Objectives
• CPC Class Codes: Y10S 977/862 Near-field probe

Abstract

A scanning probe microscope uses a high refractive index solid immersion lens (SIL) probe to provide optical images with a resolution better than the diffraction limit in air. The SIL probe has a spherical upper surface and a conical (or pyramidal) lower surface with a sharp tip. The SIL reduces the focused spot size because the spherical surface increases the angle of the marginal rays and the high refractive index material shortens the wavelength. The focused spot generates an evanescent wave having an amplitude that decays exponentially with distance from the SIL. The sharp tip on the lower surface reduces the tip-sample contact area and the tip-sample separation so that sample is within the near-field of the SIL probe. The sample perturbs the evanescent wave and a photodetector monitors characteristics of the light. A cantilever carries the SIL probe and a cantilever deflection sensor permits precise control of tip-sample forces and separation. The cantilever deflection sensor operates in a force feedback loop to maintain the tip-sample gap within the near-field as the SIL probe scans over the sample in a raster pattern to generate optical data.

Claims

1. 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 to control the distance of the probe tip on the solid immersion lens from the sample having a surface to be scanned;

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 the light emerging from the upper surface of the solid immersion lens.

2. The scanning probe optical microscope of claim 1, wherein

a) the probe tip on the second surface of the solid immersion lens forms a point;

and

b) the optical means for focusing light through the first surface of the solid immersion lens focuses light 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 light supplied to the microscope creates a small spot of light adjacent to the probe tip which may be positioned near the surface of both smooth and rough samples, and the light collected from the microscope may be detected and analyzed to measure optical characteristics of the sample and to create optical images with a resolution better than the diffraction limit in air.

3. The scanning probe optical microscope of claim 1, wherein

the probe tip on the second surface of the solid immersion lens has a large radius of curvature.

4. The scanning probe optical microscope of claim 1, wherein

a) the probe tip on the solid immersion lens is shaped to function as an atomic force microscope probe;

and

b) the vertical positioner and scanner further comprise atomic force microscope control and measurement means;

whereby the microscope may also function as an atomic force microscope.

5. The scanning probe optical microscope of claim 1, wherein

a) the first surface of the solid immersion lens has a shape corresponding substantially to one hemisphere of a geometric sphere, and

b) the probe tip on the second surface of solid immersion lens lies on an optical aplanatic surface of the geometric sphere;

whereby spherical aberration is minimized and the optical resolution of the microscope is improved.

6. The scanning probe optical microscope of claim 5, wherein the probe tip on the second surface of the solid immersion lens lies on an aplanatic surface located at a distance of r/n, with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of the geometric sphere;

whereby the solid immersion lens is a superhemispheric lens and the optical resolution of the microscope is improved.

7. The scanning probe optical microscope of claim 1, further comprising at least one spatial filter such that light within the solid immersion lens and impinging on the probe tip at angles less than the critical angle at the probe tip is reduced or substantially eliminated;

whereby the evanescent spot size is reduced, the resolution of the microscope is improved, and the far-field contribution of light is reduced or eliminated.

8. The scanning probe optical microscope of claim 1, wherein the optical means for focusing the light through the first surface of the solid immersion lens and the optical means for collecting the light emerging from the first surface of the solid immersion lens both comprise

a) a conventional optical microscope objective lens positioned above the solid immersion lens;

and

b) an optical beam-splitter positioned above the conventional microscope objective lens, such that light from a source of illumination may be directed to the objective lens, and a portion of the light coming from the solid immersion lens through the objective lens may be separately directed to detection and analysis devices.

9. The scanning probe optical microscope of claim 8, further comprising a fiber optic cable between the optical microscope objective lens and the optical beam-splitter, such that light from the beam-splitter to the objective lens and light from the objective lens to the beam-splitter is transmitted through the fiber optic cable,

whereby both a source of illumination and detection and analysis devices may be more conveniently located, thus allowing for greater flexibility in configuring the microscope, and the fiber optic cable may function as a spatial filter as in a confocal microscope, thus improving the resolution of the microscope.

10. The scanning probe optical microscope of claim 1, wherein the optical means for focusing the light through the first surface of the solid immersion lens and the optical means for collecting the light emerging from the first surface of the solid immersion lens both comprise an aspheric lens optimized for focusing on the optic axis,

whereby the size and weight of the lens is less than the size and weight of a conventional microscope objective lens.

11. The scanning probe optical microscope of claim 1, wherein the optical means for focusing the light through the first surface of the solid immersion lens and the optical means for collecting the light emerging from the first surface of the solid immersion lens both comprise a confocal microscope.

12. The scanning probe optical microscope of claim 1, wherein the vertical positioner for controlling the distance of the probe tip relative to the sample comprises

a) a cantilever onto which the solid immersion lens is mounted;

b) a cantilever deflection sensor; and

c) a cantilever positioner;

whereby the deflection of the cantilever may be sensed and the position of the probe above the sample adjusted.

13. The scanning probe optical microscope of claim 12, wherein the cantilever deflection sensor further comprises

a) a deflection sensor light source;

b) an optical signal combiner positioned above the optical means for focusing light through the first surface of the solid immersion lens, such that light from the deflection sensor light source is combined with light to be focused through the first surface of the solid immersion lens;

c) a reflective coating on a small area of the first surface of the solid immersion lens; and

d) a deflection sensor light detector;

whereby light from the deflector sensor light source may be combined with the light for illuminating the sample, reflected off the upper surface of the solid immersion lens, and detected by the deflection sensor light detector to provide a measurement of cantilever deflection.

14. The scanning probe optical microscope of claim 1, wherein the horizontal positioner further comprises a conventional scanning probe microscope XYZ positioning system.

15. The scanning probe optical microscope of claim 1, further comprising a source of light.

16. The scanning probe optical microscope of claim 15, wherein the source of light is a laser.

17. The scanning probe optical microscope of claim 15, wherein the source of light is a laser and a fiber coupling,

whereby the laser may be located remotely from the other components of the microscope, and the laser may be physically large.

18. The scanning probe optical microscope of claim 1 further comprising an optical sensor.

19. The scanning probe optical microscope of claim 18, wherein the optical sensor comprises a photodiode.

20. The scanning probe optical microscope of claim 18, wherein the optical sensor is a conventional optical microscope eyepiece or camera system and the microscope further comprises means for temporarily removing the solid immersion lens from the light path,

whereby a sample my alternately be examined by conventional optical microscopy methods.

21. 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.

22. The optical microscope of claim 21, wherein

a) the probe tip on the lower surface of the solid immersion lens is shaped to function as an atomic force microscope probe;

and

b) the microscope further comprises atomic force microscope controller;

whereby both optical information and atomic force microscope measurements may be obtained from a sample without the need to align separate optical and atomic force measuring devices.

23. The optical microscope of claim 21, wherein the atomic force microscope controller further comprises

a) means for recording the height of a sample;

b) means for positioning the probe tip to a precise distance above the sample based on the recorded height of the sample;

whereby near-field optical measurements may be made with the probe a known distance from the sample, allowing the effects of distance from sample and sample optical characteristics to be distinguished.

24. The optical microscope of claim 21, wherein the atomic force microscope controller further comprises

a) means for making and recording atomic force microscope height measurements at many points on the surface of a sample;

b) means for repositioning the probe tip over the points for which atomic force height measurements were made, at a precise distance above each point, as calculated from the atomic force microscope measurements;

whereby near-field optical measurements may be made over a large area of a sample with the effects of distance from sample and sample optical characteristics distinguished.

25. The optical microscope of claim 21, further comprising a fiber optic cable between the objective lens and the beam-splitter, such that light from the beam-splitter to the objective lens and light from the objective lens to the beam-splitter is transmitted through the fiber optic cable

whereby both a source of illumination and detection and analysis devices may be more conveniently located, thus allowing for greater flexibility in configuring the microscope, and the fiber optic cable may function as a spatial filter as in a confocal microscope, thus improving the resolution of the microscope.

26. 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.

27. The scanning probe optical microscope of claim 26, wherein the optical means for focusing light through the first surface of the solid immersion lens focuses light 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.

28. The scanning probe optical microscope of claim 26, wherein

a) the probe tip on the solid immersion lens is shaped to function as an atomic force microscope probe;

and

b) the vertical positioner further comprises atomic force microscope control and measurement means;

whereby the microscope may also function as an atomic force microscope.

29. The scanning probe optical microscope of claim 26, wherein

a) the first surface of the solid immersion lens has a shape corresponding substantially to one hemisphere of a geometric sphere;

and

b) the probe tip on the second surface of solid immersion lens lies on an optical aplanatic surface of the geometric sphere;

whereby spherical aberration is minimized and the optical resolution of the microscope is improved.

30. The scanning probe optical microscope of claim 29, wherein the probe tip on the second surface of the solid immersion lens lies on an aplanatic surface of the geometric sphere located at a distance of r/n, with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of geometric sphere,

whereby the solid immersion lens is a superhemispheric lens and the optical resolution of the microscope is improved.

31. The scanning probe optical microscope of claim 26, further comprising a spatial filter to selectively filter the light to be focused through the first surface of the solid immersion lens, such that light impinging on the probe at less than the critical angle is reduced or substantially eliminated,

whereby the evanescent spot size is reduced, the resolution of the microscope is improved, and the far-field contribution of light is reduced or eliminated.

32. The scanning probe optical microscope of claim 26, further comprising an opaque coating on a portion of the first surface of the solid immersion lens, such that light which would impinge on the probe tip at less than the critical angle is blocked,

whereby the evanescent spot size is reduced, the resolution of the microscope is improved, and the far-field contribution of light is reduced or eliminated.

33. The scanning probe optical microscope of claim 26, wherein the optical means for focusing the light through the first surface of the solid immersion lens comprises a conventional optical microscope objective lens positioned above the solid immersion lens.

34. The scanning probe optical microscope of claim 26, wherein the optical means for focusing the light through the first surface of the solid immersion lens and the optical means for collecting the light emerging from the first surface of the solid immersion lens both comprise an aspheric lens optimized for focusing on the optic axis,

whereby the size and weight of the lens is less than the size and weight of a conventional microscope objective lens.

35. The scanning probe optical microscope of claim 26, wherein the vertical positioner for controlling the distance of the probe tip relative to the sample comprises

a) a cantilever onto which the solid immersion lens is mounted;

b) a cantilever deflection sensor; and

c) a cantilever positioner;

whereby the deflection of the cantilever may be sensed and the position of the probe above the sample adjusted.

36. The scanning probe optical microscope of claim 26, wherein the scanner for translating the solid immersion lens and the sample support relative to one another along a substantially horizontal plane comprises a conventional scanning probe microscope XYZ positioning system.

37. The scanning probe optical microscope of claim 26, wherein

a) a portion of the sample support is transparent;

and

b) the optical means for collecting light from the sample further comprises optical light collection means located below the transparent support for the sample to be scanned;

whereby translucent samples may be examined with light transmitted through the sample.

38. The scanning probe optical microscope of claim 26, wherein the optical means for collecting light from the sample further comprises optical light collection means located above the sample,

whereby samples may be examined with the light scattered from the surface of the sample.

39. The scanning probe optical microscope of claim 26 further comprising a source of light.

40. The scanning probe optical microscope of claim 26, wherein the source of light is a laser.

41. The scanning probe optical microscope of claim 40, wherein the source of light is a laser and a fiber coupling,

whereby the laser may be located remotely from the other components of the microscope.

42. The scanning probe optical microscope of claim 26 further comprising an optical sensor.

43. The scanning probe optical microscope of claim 42, wherein the optical sensor comprises a photodiode.

44. 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.

45. The combined scanning probe optical microscope and atomic force microscope of claim 44, wherein

a) the first surface of the solid immersion lens has a shape corresponding substantially to one hemisphere of a geometric sphere;

and

b) the probe tip on the second surface of solid immersion lens lies on an optical aplanatic surface of the geometric sphere;

whereby spherical aberration is minimized and the optical resolution of the microscope is improved.

46. The combined scanning probe optical microscope and atomic force microscope of claim 44, wherein the probe tip on the second surface of the solid immersion lens lies on the aplanatic surface located at a distance of r/n, with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of the lens,

whereby the solid immersion lens is a superhemispheric lens and the optical resolution of the microscope is improved.

47. The combined scanning probe optical microscope and atomic force microscope of claim 44 further comprising one or more spatial filters to selectively filter light such that light impinging on the probe at less than the critical angle is reduced or substantially eliminated,

whereby the evanescent spot size is reduced, the resolution of the microscope is improved, and the far-field contribution of light is reduced or eliminated.

48. The combined scanning probe optical microscope and atomic force microscope of claim 44, wherein the optical means for focusing the light through the first surface of the solid immersion lens comprises an aspheric lens optimized for focusing on the optic axis,

whereby the size and weight of the lens is less than the size and weight of a conventional microscope objective lens.

49. The combined scanning probe optical microscope and atomic force microscope of claim 44, wherein the position control mechanism for controlling the position of a sample with respect to the base end of the cantilever and the means for recording vertical and horizontal position data of the probe tip further comprise scan control and scan recording means.

50. 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.

51. The combined scanning probe optical microscope and atomic force microscope of claim 50, wherein

a) the first surface of the solid immersion lens has a shape corresponding substantially to one hemisphere of a geometric sphere;

and

b) the probe tip on the second surface of solid immersion lens lies on an optical aplanatic surface of the geometric sphere;

whereby spherical aberration is minimized and the optical resolution of the microscope is improved.

52. The combined scanning probe optical microscope and atomic force microscope of claim 50, wherein the probe tip on the second surface of the solid immersion lens lies on an aplanatic surface of the geometric sphere located at a distance of r/n , with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of the geometric sphere,

whereby the solid immersion lens is a superhemispheric lens and the optical resolution of the microscope is improved.

53. The combined scanning probe optical microscope and atomic force microscope of claim 50 further comprising one or more spatial filters to selectively filter light such that light impinging on the probe at less than the critical angle is reduced or substantially eliminated,

whereby the evanescent spot size is reduced, the resolution of the microscope is improved, and the far-field contribution of light is reduced or eliminated.

54. The combined scanning probe optical microscope and atomic force microscope of claim 50, wherein the optical means for focusing the light through the first surface of the solid immersion lens comprises an aspheric lens optimized for focusing on the optic axis,

whereby the size and weight of the lens is less than the size and weight of a conventional microscope objective lens.

55. The combined scanning probe optical microscope and atomic force microscope of claim 50, wherein the position control mechanism for controlling the position of a sample with respect to the base end of the cantilever and the means for recording vertical and horizontal position data of the probe tip further comprise scan control and scan recording means.

56. 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.

57. The method of claim 56, wherein the first surface of the solid immersion lens positioned near the surface to be illuminated has a shape corresponding substantially to one hemisphere of a geometric sphere and the probe tip is formed on a geometric aplanatic surface of the geometric sphere,

whereby spherical aberration is eliminated and the spot size is minimized.

58. The method of claim 57, wherein the probe tip on the second surface of the solid immersion lens lies on an aplanatic surface of the geometric sphere located at a distance of r/n , with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of the geometric sphere,

whereby the solid immersion lens is a superhemispheric lens and the size of the illumination spot is further reduced.

59. The method of claim 56 further comprising the step of spatially filtering the light to be focused on the solid immersion lens to eliminate rays which would impinge the probe tip at less than the critical angle,

whereby the size of the illumination spot is further reduced and the contribution of far-field light is reduced or eliminated.

60. 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.

61. The method of claim 60, wherein the first surface of the solid immersion lens positioned near the surface to be illuminated has a shape corresponding substantially to one hemisphere of a geometric sphere, and the probe tip is formed on an aplanatic surface of the geometric sphere,

whereby spherical aberration is eliminated and the spot size is minimized.

62. The method of claim 61, wherein the probe tip on the second surface of the solid immersion lens lies on an aplanatic surface located at a distance of r/n, with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of the geometric sphere,

whereby the solid immersion lens is a superhemispheric lens and the size of the illumination spot is further reduced.

63. The method of claim 60, further comprising the step of annularly filtering the light to be focused on the solid immersion lens to eliminate rays which would impinge the probe tip at less than the critical angle,

whereby the size of the illumination spot is further reduced and the contribution of far-field light is reduced or eliminated.

64. 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.

65. The method of claim 64, wherein the first surface of the solid immersion lens positioned near the surface to be illuminated has a shape corresponding substantially to one hemisphere of a geometric sphere, and the probe tip is formed on an aplanatic surface of the geometric sphere,

whereby spherical aberration is eliminated and the spot size is minimized.

66. The method of claim 65, wherein the probe tip on the second surface of the solid immersion lens lies on the aplanatic surface located at a distance of r/n, with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of the geometric sphere,

whereby the solid immersion lens is a superhemispheric lens and the size of the illumination spot is further reduced.

67. The method of claim 64, further comprising the step of spatially filtering the light to be focused on the solid immersion lens to eliminate rays which would impinge the probe tip at less than the critical angle,

whereby the size of the illumination spot is further reduced and the contribution of far-field light is reduced or eliminated.

68. 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.

69. The method of claim 68, wherein the first surface of the solid immersion lens positioned near the surface to be illuminated has a shape corresponding substantially to one hemisphere of a geometric sphere, and the probe tip is formed on an aplanatic surface of the geometric sphere,

whereby spherical aberration is eliminated and the spot size is minimized.

70. The method of claim 69, wherein the probe tip on the second surface of the solid immersion lens lies on an aplanatic surface of the geometric sphere located at a distance of r/n, with r being the radius of the lens and n being the index of refraction of the lens material, from the equatorial plane of the geometric sphere,

whereby the solid immersion lens is a superhemispheric lens and the size of the illumination spot is further reduced.

71. The method of claim 68, further comprising the step of annularly filtering the light to be focused on the solid immersion lens to eliminate rays which would impinge the probe tip at less than the critical angle,

whereby the size of the illumination spot is further reduced and the contribution of far-field light is reduced or eliminated.