Q-Switched Laser With Increased Pulse Power

A pulsed output with a power of dozens of watts and a pulse width of 40 ns was obtained through an MO Q-switched laser controlled by labyrinth-shaped magnetic domains (Source: Toyohashi Univ.)

A pulsed output with a power of dozens of watts and a pulse width of 40 ns was obtained through an MO Q-switched laser controlled by labyrinth-shaped magnetic domains (Source: Toyohashi Univ.)

The “Industry 4.0” concept, first introduced by the German government, has recently extended the scope of compact high-power laser appli­cations to, for instance, laser manu­facturing, vehicle engine deve­lopment, or thruster systems for space explo­ration. However, integration of a control­lable Q-switch into compact solid-state lasers has been chal­lenging because of the mechanisms of EO and AO effects. In addition, previous Q-switches needed a large-sized power supply, which prevented down­scaling of the entire system.

Now, researchers at Toyohashi University of Technology, Iowa State University, and the Institute for Molecular Science have developed a magneto-optic (MO) Q-switched laser for the first time, using a 190-micron-thick magnetic garnet film with labyrinth-shaped magnetic domains. They used custom-made coil and circuits to generate the pulsed magnetic field to be applied to the magnetic garnet, and success­fully generated optical output with a pulse width of tens of nano­seconds. This is the first demon­stration ever of a Q-switched laser driven by magnetic domain motions, and also the first evidence of the possi­bility of an integrated Q-switched laser. “The device was two orders of magni­tude smaller than other reported control­lable Q-switches,” commented Takunori Taira.

“The most difficult part of realizing MO Q-switching was to combine three different tech­niques/fields: the prepa­ration of a magnetic material, the fabrication of a high-speed magnetic field switch, and the con­struction of a laser cavity,” explained Ryohei Morimoto. According to Taichi Goto, “there are no previous reports of MO Q-switches using thin garnets. This is surely the first demon­stration, and it also becomes an important first step in the deve­lopment of an inte­grated high-power laser.”

“We enjoy our colla­boration and learn from each other,” said Mina Mani. “We further hope not only to advance research and create and pursue new challenges, but also to use science and techno­logy to make a better world for all.” In addition, the researchers found a unique biasing tech­nique that uses magnetism to decrease the electric power needed for Q-switching. When a ring-shaped permanent magnet was placed close to the magnetic garnet, they were able to generate the same optical pulse in the MO Q-switched laser using seven times less electric power. This result showed that this Q-switch does not need a large power supply for ope­ration, meaning that drastic down­scaling can be expected. The research team would like their future studies to be useful for laser users all around the world and to help in the esta­blishment of new industries. (Source: Toyohashi Univ.)

Reference: T. Goto et al.: Magneto-optical Q-switching using magnetic garnet film with micro magnetic domains, Opt. Exp. 24, 17635 (2016); DOI: 10.1364/OE.24.017635 

Link: Dept. of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Japan

Speak Your Mind

*