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HOME > No.13, May 2018 > New Smaller Laser Achieved One-Digit Higher Output

New Smaller Laser Achieved One-Digit Higher Output

By using randomly polarized laser beam with a "Q switch" By Taichi Goto
Hitoshi Isahara

Taichi Goto at Toyohashi University of Technology and his international research team have produced the first high-powered, randomly polarised laser beam with a “Q switch” laser, which typically emits pulses of light so brief that they’re measured in Kilowatts per nanosecond. Lasers are a critical part of modern technology—they’re used in everything from our automobiles to medical equipment to the satellites orbiting Earth. Now, researchers are broadening the potential applications of even smaller and more powerful lasers.

“The experimental evidence provided in this study advances this research field toward the realization of actively controllable integrated micro lasers,” said Taichi Goto, second author of the paper and an assistant professor in the Department of Electrical and Electronic Information Engineering at Toyohashi University of Technology.

Fig.1 The first high-powered, randomly polarized laser beam with a “Q switch” laser. Optical pulses were controlled by electrical signals.

Other study contributors include scientists from the Institute for Molecular Science at the Laser Research Centre in Japan and the Electrical and Computer Engineering Department at Iowa State University in the United States.

Fig.2 Obtained optical pulse. The peak power was about 1 kW. The pulse width was 25 ns.

Q switch lasers are used in a variety of applications, including in surgical procedures, and can produce more precise results with less damage than traditional tools. The lasers require integration of active and passive responsibilities for maximum efficiency.

"There are two advantages to actively controlling integrated micro lasers," said Goto. “Firstly the small size of the lasers allows for the use of mass production techniques. Secondly, the price of each Q switch laser can be lowered thanks to the integration.”

A technique called Q switching produces short but high-powered pulse outputs. As in other lasers, an electric current excites electrons in a laser medium − in this case, it’s a crystal used in solid-state lasers − and emits the resulting energy as amplified light. The light can be polarized in one direction or another, but it’s nearly impossible to change the randomly polarized light in a small Q switch laser.

Goto and his team used Q switching, along with a laser a tenth of the size of one cent, to produce a laser beam ten times more powerful than previously reported with larger lasers.

Fig.3 The world-first achievement of a randomly polarized (unpolarized) light generated using an magneto-optical Q-switched laser may lead to groundbreaking new fields of applications.

Along with the change of laser size, the researchers also adjusted the magnetic material through which the light travels and amplifies to a more powerful pulse. With the addition of a neodymium-yttrium-aluminum-garnet, Goto could use magneto-optics to better control how the light moves within the laser cavity.

The short pulses allow the researchers to change the polarization of the laser through manipulation of the photons comprising the light. Instead of a constant light, each pulse can be switched. The laser size means the energy punches out, instead of dissipating as it travels inside the system.

The researchers plan to increase the peak power of their system, according to Goto. They also plan to apply the system as an integrated micro laser for further testing.


Ryohei Morimoto, Taichi Goto, Takunori Taira, John Pritchard, Mani Mina, Hiroyuki Takagi, Yuichi Nakamura, Pang Boey Lim, Hironaga Uchida and Mitsuteru Inoue, "Randomly polarised beam produced by magnetooptically Q-switched laser", Scientific Reports, 7, 15398 (2017).


By 後藤 太一




そのしくみについて、「レーザーを形作る共振器(キャビティー)を、他の制御可能なQスイッチ素子では達成が難しい10 mmまで縮めることで、パルス幅を短くしています。」と本論文の責任著者の後藤助教は、述べています。




  • 日本学術振興会 科研費 26220902, 17K19029, 17J05958
  • 国立研究開発法人 科学技術振興機構 さきがけ JPMJPR1524
  • 矢崎科学技術振興記念財団

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Researcher Profile

Taichi Goto
Name Taichi Goto
Affiliation Department of Electrical and Electronic Information Engineering
Title Assistant Professor
Fields of Research Magnetics / Optics/ Photonics/ Nanotechnology/ Spintronics/ Magnonics