Pulsed laser

infraredYAG

In the thin-disk laser system, the laser active medium is a very thin disk with less than 200-μm thickness. The Yb:YAG crystal is stimulated at the frontside via a diode laser stack in a quasi-end-pumped design. The backside is cooled over the whole area. Due to the small thickness, only a part of the pump beam is absorbed. In an optical system consisting of one parabolic mirror and one retro-reflective mirror (refer to diagram), the not-absorbed power on each disk will be imaged multiple times from each diode laser system to optimize efficiency. Typically, up to 32 passes of each pump beam are realized. A single disk can produce up to 3.5 kilowatts of power, and these lasers operate in the near-infrared at a wavelength of 1.03 μm. Through innovative designs, such as the one diagrammed above, multiple disks can be cascaded to achieve higher power levels. Because the disk can be cooled over its entire backside, thermal lensing is kept to a minimum. Heat flow and temperature gradients predominantly occur on-axis, resulting in an almost homogeneous distribution of temperature and minimal distortions of the wavefront. Due to these advantages, it is possible to achieve excellent beam quality even at high laser powers. Depolarization caused by the active medium is also very low. Furthermore, simple power scalability can be achieved through variation of the pumped diameter and pump power.