Patent ID: 7280567

Claim:
A fiber upconversion laser for producing visible output at multiple wavelengths including the wavelengths of blue, green, orange and red light comprising: an optical fiber including multiple waveguide gain regions embedded within a common inner cladding of lower refractive index, wherein each gain region supports propagation of only a single transverse mode of optical radiation at one wavelength therein, and is within an outer cladding of lower refractive index than the cladding material forming said inner cladding, wherein each of said waveguide gain regions are doped with one or more active ionic species; reflectors, defining an optical cavity, for providing optical feedback of said optical radiation propagating within each of said waveguide gain regions to establish resonant laser conditions for each of said gain regions; and a light pump for producing an excitation beam and pumping one or more active ionic species by one or multiple pump wavelengths from one or both ends of the optical fiber, wherein one or more Large Mode Area (LMA) waveguide gain regions are doped with Pr 3+ ions to a concentration of less than 0.5 wt % and greater than 0.05 wt % Yb 3+ ions to a concentration of greater than 0.5 wt % wherein for said Pr 3+ ions and said Yb 3+ ions, said excitation beam between 780 nm and 900 nm excites populations of said Yb 3+ ions which thereafter transfer energy to populations of said Pr 3+ ions which are independently excited by said excitation beam to an energy level from which said populations of said Pr 3+ ions and said populations of said Yb 3+ ions participate in a photon avalanche process which increases said populations of said Pr 3+ ions at said energy level, said populations of said Pr 3+ ions lasing at said multiple wavelengths of blue, green, red and orange visible light.