Spectral filter for high-power fiber illumination sources

A filtered fiber illumination source comprising:

• a fiber illumination source configured to provide broadband illumination diverging from an output face of an optical fiber;
• a curved filtering element including a concave surface forming a portion of a sphere, the concave surface formed as a polished optical surface, the concave surface positioned to receive the broadband illumination diverging from the output face of the optical fiber, the output face of the optical fiber positioned at a first location proximate to a center of the sphere, the concave surface further including a wavelength-selective coating configured to transmit a first portion of a spectrum of the broadband illumination and reflect a second portion of the spectrum of the broadband illumination, wherein the first and second portions of the spectrum provide a broadband spectral range separated by a selected cutoff wavelength such that the wavelength-selective coating is one of a high-pass or a low-pass spectral filter with respect to the selected cutoff wavelength, the concave surface further configured to reflect and focus the second portion of the spectrum to a second location proximate to the center of the sphere;
• and
• a collector configured to direct the second portion of the spectrum away from the output face of the optical fiber.

A method for filtering illumination from an optical fiber comprising:

• receiving illumination from an output face of an optical fiber with a curved filtering element including a concave surface forming a portion of a sphere, the concave surface formed as a polished optical surface, the concave surface positioned to receive light diverging from an output face of an optical fiber positioned at a first location proximate to a center of the sphere;
• transmitting, with a wavelength-selective coating on the concave surface, a first portion of a spectrum of the illumination;
• reflecting, with the wavelength-selective coating on the concave surface, a second portion of the spectrum, wherein the first and second portions of the spectrum provide a broadband spectral range separated by a selected cutoff wavelength such that the wavelength-selective coating is one of a high-pass or a low-pass spectral filter with respect to the selected cutoff wavelength;
• focusing, with the concave surface, the second portion of the spectrum to a second location proximate to the center of the sphere;
• and
• directing, with a collector, the second portion of the spectrum away from the output face of the optical fiber.