30-W Fiber-coupled Laser-diode Optical Module for Medical Applications

We developed the fiber-coupled optical module using two laser diode arrays (LDAs) at the wavelength of 1460 nm for medical applications because the wavelength of around 1460 nm has an absorption peak for fat and water simultaneously. We combine two beams from the two LDAs by spatial multiplexing. The two beams of the LDAs vertically collimated and rotated by micro optics, called a beam-transformation system (BTS), are collimated to be parallel by using a cylindrical lens and are combined by using a folding mirror carefully with different height. Then, the parallel beams are focused by using an aspheric lens and are coupled to a fiber with a core diameter of 600 urn and a numerical aperture of 0.37. The maximum optical power is 31 W at the end of the fiber. The corresponding coupling efficiency is 82.4% at a current of 50 A and at a temperature of 20 degrees C. The result shows a total optical system efficiency of 77% from 2 LDAs to the end of fiber.