Fiber-optic based surface spectroscopy

A method for performing surface-sensitive spectroscopic characterizations on a surface to be interrogated, comprising:

• a) directing a first input from a first optical source, through a first input optical fiber and to a first position proximate a location on a surface to be interrogated, said first input comprising a fixed wavelength laser;
• b) utilizing first input fiber coupling optics for receiving said first input from an output end of said first input optical fiber and delivering said first input to the interrogated location on the surface;
• c) directing a second input from a second optical source, through a second input optical fiber to a second position proximate the interrogated location, second input comprising a tunable wavelength laser, said first and second inputs being aligned so that their surface locations of optical illumination overlap on said interrogated location;
• d) receiving, via output fiber coupling optics, a reflected output resulting from a nonlinear three-wave mixing process of said first and second inputs being aligned so that their surface locations of optical illumination overlap on said interrogated location, said nonlinear three-wave mixing process comprising sum-frequency generation and difference frequency generation occurring at said interrogated location, further including:
• positioning said output fiber coupling optics between the reflection of said first input from the surface and the reflection of said second input from the surface for a sum-frequency output propagation direction and positioning said output fiber coupling optics below both the reflection of said first input from the surface and the reflection of said second input from the surface for a difference-frequency output propagation direction:
• e) receiving an output of said output fiber coupling optics, via an output optical fiber, and transmitting the output to a desired third position from said interrogated location;
• and
• f) receiving an output of said output optical fiber end collecting, analyzing and interpreting said output of said output optical fiber, wherein said first and second optical sources and said output sensor system may be disposed at desired distances and angles from said interrogated location.

A fiber-based nonlinear optical system for performing surface-sensitive spectroscopic characterizations on a surface to be interrogated, comprising:

• a) a first optical source for providing a first input, said first optical source comprising a fixed wavelength laser;
• b) a first input optical fiber for receiving said first input and transmitting said first input to a first position proximate a location on a surface to be interrogated;
• c) first input fiber coupling optics for receiving said first input from an output end of said first input optical fiber and delivering said first input to the interrogated location on the surface;
• d) a second optical source for providing a second input, said second optical source comprising a tunable wavelength laser;
• e) a second input optical fiber for receiving said second input and transmitting said second input to a second position proximate the interrogated location;
• f) second input fiber coupling optics for receiving said second input from an output end of said second input optical fiber and delivering said second input to the interrogated location on the surface, said first and second inputs being aligned so that their surface locations of optical illumination overlap on said interrogated location;
• g) output fiber coupling optics for receiving a reflected output resulting from a nonlinear three-wave mixing process of said first and second inputs being aligned so that their surface locations of optical illumination overlap on said interrogated location, occurring at said interrogated location, said nonlinear three-wave mixing process comprising difference-frequency generation, wherein:
• said output fiber coupling optics are positioned below both the reflection of said first input from the surface and the reflection of said second input from the surface for a difference-frequency output propagation direction:
• h) an output optical fiber for receiving an output of said output fiber coupling optics and transmitting the output to a desired third position from said interrogated location;
• and
• i) an output sensor system for receiving an output of said output optical fiber and collecting, analyzing and interpreting said output of said output optical fiber, wherein said first and second optical sources and said output sensor system may be disposed at desired distances and angles from said interrogated location.