The hottest research team made a major breakthroug

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The research team has made a major breakthrough in the research of terahertz photonics components

quantum cascade laser (QCL) is a semiconductor laser operating in the medium and long infrared and terahertz range. In QCL, electrons are responsible for emitting photons into subsequent quantum wells, so an electron can produce several photons, which is very efficient. The transition from one quantum well to the upper limit of cloth hardness hb650, which cannot be higher than this value, to another quantum well is called "quantum cascade". Photo source: Luo ()

recently, a research team from Germany, Italy and the UK successfully developed a key photon component, which realizes the super coupling between the subband transition of semiconductor quantum wells and the photon mode of metal cavities. It is expected to use saturable absorbers (SA) to manufacture cheap quantum cascade lasers (QCL) that can trigger short terahertz pulses. This will become an important milestone on the road of terahertz application. Relevant results were published in the recent nature communication

terahertz wave refers to the electromagnetic wave whose frequency is between microwave and infrared. Because of its special nature, it has a wide application potential. Such as airport security scanners, trace gas detection, ultra-high speed communication technology and medical technology. However, the current commercial terahertz source can only operate in continuous wave mode. Therefore, the development of compact quantum cascade lasers that are cheap and can produce few or even single period pulses to replace desktop laser sources with complex and expensive structures will accelerate various exciting applications in the terahertz field

the emission process of quantum cascade lasers is based on the inter subband (ISB) transition in the semiconductor multi quantum well (MQW) structure. Passive mode locking using a saturable absorber is a method of generating ultrashort pulses in lasers. This mode requires saturable absorbers with short response time and low saturation threshold, but saturable absorbers for terahertz spectral range have been difficult to achieve, and the required light intensity is far beyond the capacity of quantum cascade lasers

now, the research team has successfully placed the slider fixed with the sample in the center of the first sample without impact to emit a microstructure device composed of a gold mirror and a gold grid, which together constitute a resonant body of terahertz radiation. Its resonance can be closely coupled with electrons in special semiconductor nanostructures. Through the observation of high-precision slow motion camera, it is found that the new structure responds well to the stimulation of strong terahertz printing test report pulse, and the absorber reaches saturation on the femtosecond time scale. Intense light pulses can convert saturable absorbers (Golden grids) into almost perfect mirrors. The required light intensity is ten times lower than that of a single pure semiconductor structure, and the reaction is faster than the single light oscillation of terahertz pulses

professor Mirian vidiero of Italy's National Nanotechnology Center said, "we now have all the necessary components for manufacturing ultrafast quantum cascade lasers using saturated absorbers." Terahertz is expected to become a reality in many fields, including telecommunications, chemical analysis and medical diagnosis. Because the oscillation rate of terahertz radiation is thousands of times faster than the clock rate of the current generation of computers, ultrashort terahertz pulses can achieve a new generation of telecommunications connections, and are considered to be one of the most potential 6G technologies

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