Patent ID: 7391795

Claim:
A laser light source comprising a first laser for generating a laser beam of a wavelength λ 1 , a second laser for generating a laser beam of a wavelength λ 2 , and a nonlinear optical crystal that uses the laser beam of the wavelength λ 1 and the laser beam of the wavelength λ 2 as inputs and outputs a coherent beam having a wavelength λ 3 of a sum frequency that satisfies a relationship of 1/λ 1 +1/λ 2 =1/λ 3 , comprising: two polarization maintaining fibers coupled to outputs of the first and second lasers, respectively; and a multiplexer for multiplexing outputs of the two polarization maintaining fibers and coupling a multiplexed output to the nonlinear optical crystal, wherein the second laser is a semiconductor laser and the first laser oscillates in a multimode, wherein the nonlinear optical crystal has a periodically poled structure and a length of the nonlinear optical crystal is 10-60 mm, wherein the polarization maintaining fiber coupled to the output of the first laser has a fiber Bragg grating with a full width of half maximum of 0.5 or less and the first laser and the fiber Bragg grating are configured as a resonator structure, and wherein the wavelength λ 3 of a sum frequency is a wavelength of 589.3±2 nm that is equivalent to the sodium D line.