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Hamamatsu produces terahertz waves at 450 ¦Ìm
date£º2019-12-12 09:53:16 Click No.£º613

Source: optics.org

Said to be ¡°world¡¯s longest wavelength¡± output from a single semiconductor laser.

Terahertz nonlinear QCL emits at a wavelength of 450 ¦Ìm. Image: Hamamatsu.

Hamamatsu Photonics has announced that it has succeeded in producing terahertz waves at a wavelength of 450 ¦Ìm in the terahertz range, which the Japanese photonics giant says is ¡°the world¡¯s longest wavelength available from a single semiconductor laser operating at room temperature.¡±

In its launch announcement, the company stated, ¡°To achieve this breakthrough, we have developed long-wavelength mid-infrared quantum cascade laser, in which we designed the laser structure based on research and analysis results of the terahertz wave generation principle.

¡°Results from this research will be useful in applications such as quality testing and non-destructive inspection of drugs and foods containing components that absorb electromagnetic waves in the sub-terahertz range as well as submillimeter astronomy and high-speed and high-capacity communication over short distances.¡± Details of the research supporting this development were published in the journal Nanophotonics.

Background to research

In 2018, Hamamatsu developed a ¡°terahertz nonlinear quantum cascade laser", employing an anti-crossed dual-upper-state design (AnticrossDAUTM). This QCL produces two mid-infrared rays at different wavelengths within a range from 6 to 11 ¦Ìm from a single semiconductor device and induces a nonlinear optical effect inside the device.

The QCL acts as a single compact semiconductor laser that operates at room temperature and generates terahertz waves up to a wavelength of 150 ¦Ìm. To generate electromagnetic waves at even longer wavelengths in the sub-terahertz range, it is necessary to produce two mid-infrared rays at longer wavelengths. This has been extremely difficult to achieve since the longer wavelength light is likely to be absorbed within the device.

The researchers commented, ¡°We investigated the characteristics of many QCLs to clarify wavelength conversion process in a terahertz nonlinear QCL. We found that we can apply the theory of a nonlinear optical effect, called coherent optical rectification, which had not been evaluated before.

¡°By applying this theory to the wavelength conversion mechanism using the nonlinear optical effect, we optimized the anti-crossed dual-upper-state design to suppress the unwanted absorption of light inside the device, thus allowing output of the two mid-infrared light rays at longer wavelengths up to 14 ¦Ìm and also increased the wavelength conversion efficiency. In this way, we succeeded in outputting terahertz waves at 450 ¦Ìm in the terahertz range which is the world¡¯s longest wavelength available from a single semiconductor laser operating at room temperature.¡±

Other possible applications also include submillimeter astronomy for studying the birth and formation process of stars by observing dust and gases in outer space that cannot be seen with visible light and infrared light. Since the wavelength of terahertz waves is shorter than radio waves commonly used for communication and propagate in the air to some extent, they can be used for high-speed and high-capacity communication over short distances such as within a home, office, or data center.

In the future, Hamamatsu says it plans to develop devices with higher power output by increasing the terahertz wave output efficiency by improving the design of the QCL structure as well as applying a light out-coupling structure and appropriate material for the semiconductor substrate.

 
 

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