Capillary wall coupled whispering gallery mode microresonator

A microresonator structure comprising:

• a waveguide of elongated cylindrical shape including:
• a first optical fiber including a central core and surrounding cladding, and
• a capillary of optical transmission material coupled to the first optical fiber, the capillary forming a cavity section including a first hollow cavity adjacent to the first optical fiber including a first sidewall with an inner surface that tapers inward to an apex positioned adjacent to the first optical fiber and a second hollow cavity positioned adjacent to the first cavity of cylindrical shape including a circumferential second sidewall that abuts the first sidewall;
• and
• a microsphere with a spherical outer surface, the microsphere positioned within the cavity section such that the outer surface contacts a portion of the first sidewall and a portion of the second sidewall,
• wherein a portion of light coupled into the first section of the waveguide is coupled into the microsphere where the microsphere contacts the waveguide.

A method of forming a microresonator structure, the method comprising the steps of:

• coupling a first end of a hollow cylindrical capillary to a first optical fiber;
• forming an inwardly tapering inner surface of a sidewall of the capillary, wherein the inner surface defines a portion of a hollow cavity;
• placing a microsphere in the cavity so that the microsphere contacts the inner surface;
• sealing a second end of the capillary with a second optical fiber;
• and
• reducing the thickness of the sidewall of the capillary.