High Output Generation of Green Laser without Resonator

Applications from Laser Theater to Laser Processing are now within View

2008.03.25

National Institute for Materials Science
University of Tokyo

The National Institute for Materials Science and The University of Tokyo produced a high efficiency wavelength conversion device in stoichiometric lithium tantalate (LiTaO3; abbreviated SLT), which had been developed independently by NIMS, and realized a continuous 16W green light without a resonator using a high quality, high output laser developed by the University of Tokyo.

Abstract

  1. A group including Senior Researcher Sunao Kurimura of the National Institute for Materials Science (President: Prof. Teruo Kishi) and Associate Prof. Norikatsu Mio and others of the Graduate School of Frontier Sciences, University of Tokyo produced a high efficiency wavelength conversion device in stoichiometric lithium tantalate (LiTaO3; abbreviated SLT), which had been developed independently by NIMS, and realized a continuous 16W green light without a resonator using a high quality, high output laser developed by the University of Tokyo.
  2. Because no semiconductor lasers exist in the green wavelength region, the method of obtaining a green laser by wavelength conversion from a red laser has generally be adopted. In laser television and similar applications, an output on the order of 3W is required, while an output of 10W or more is needed in laser theater. If it is possible to exceed 10W, application to laser processing such as laser trimming and laser marking can also be expected. However, with conventional single pass wavelength conversion, it was extremely difficult to obtain outputs of 10W and higher. In realizing a compact, low cost green laser, single pass wavelength conversion without using a resonator is advantageous. Resonators are sensitive to vibration and changes in temperature, and a high degree of experience is necessary in adjustments, resulting in increased costs. In this research, output of 16W, which exceeded the current world’s record by 50%, was realized by continuous oscillation) wavelength conversion in the green wavelength region without a resonator. The previous record of 10.5W was held by Stanford University.
  3. In realizing a high output laser, it is important to exhaust heat from the device efficiently. Therefore, the wavelength conversion device was realized by creating a polarity reversing structure having a very small periodical distance of 8μm in an SLT wavelength conversion material, which has high heat conductivity. Temperature rise in the device was minimized by designing a heat exhaust type wavelength conversion module for high output wavelength conversion. Wavelength conversion with both high efficiency and high output was possible by using a high quality single frequency 100W laser developed independently by the University of Tokyo.
  4. In the wavelength conversion technology developed in this research, high efficiency is realized without using a resonator. As a result, precise optical adjustments are not necessary, and operation is stable in vibrating condition. Thus, this can be considered a suitable wavelength conversion method for severe fields such as laser processing. Furthermore, as it was confirmed that the wavelength conversion device can be operated up to high outputs, long life can be expected in the low output region.
  5. These research results are scheduled to be presented at the Meeting of the Japan Society of Applied Physics in March and at the Conference on Lasers and Electro-Optics, which is an international conference to be held in early May.
"Fig.:Wavelength conversion moduleThe wavelength conversion device is inserted in the heat exhausting module.The wavelength conversion material is high thermal conductivity Mg: SLT." Image

Fig.:Wavelength conversion module
The wavelength conversion device is inserted in the heat exhausting module.The wavelength conversion material is high thermal conductivity Mg: SLT.