Side-Pumping Diodes Mean More Power for Materials Processing

Kathleen G. Tatterson

SUNNYVALE, Calif. -- A novel technology in which a side-pumped laser diode drives a solid-state laser source could mean more power and greater precision for materials processing applications, say the scientists who developed it.
Use of diode lasers as pumping sources has traditionally been limited to low-power lasers (up to a few watts) because their end-pumping designs have little input power capability and are generally inefficient in sustaining beam quality at higher pump powers. Researchers at Power Path Technology have demonstrated that their technique can generate power up to 15 W.
"Our technique allows us to make better use of the pump light, and to extract not just the power out of the laser configuration, but also the power in a highly usable TEM₀₀ mode volume," explained Jim Darchuk, director of marketing.TEM₀₀ mode allows for a more controllable, efficient light source. "It's analogous to using a sharp tool vs. a blunt tool," he said.

Gain region created

The side-pump assembly comprises arrays of series-wired diode lasers and cylindrical lenses that collect, collimate and direct light into the sides of a laser material, either an Nd:YAG or Nd:YLF slab. This creates a gain region in the slab, where the light passes through the rod several times, producing an optical path in and out of the ends of the rod via a network of optical elements. The multipass optical path, where the beams run tangent or slightly overlap each other, creates the gain aperturing that enables the laser to support only TEM₀₀ operation.
Darchuk said that the life expectancy for the pump assembly exceeds 10,000 h and that it is easy to change the number of diode elements to generate the pump light required for the specific application. Also, the design allows a technician to easily replace the assembly in the field. The company currently offers continuous-wave lasers with 7- and 10-W capabilities using the side-pump design. With these instruments as a starting point, Power Path plans to manufacture and market lasers with higher output capabilities for applications such as micromachining and part marking.