The use of lasers to turn light beams into intense monochromatic radiation has completely changed the way we live and work. It has been more than 50 years old. Its numerous applications include: Ultrafast and high-throughput data communication, manufacturing , Surgical, bar code scanners, printers, driverless technology and laser projection displays. Lasers are also used in atomic and molecular spectroscopy and can be used for the detection and analysis of various types of scientific branches and various chemical substances and biomolecules.
Lasers can be classified according to their emission wavelength within the electromagnetic spectrum. For example, visible lasers such as laser pointers are only a small part of them. Infrared lasers can be used for optical communication through optical fibers; ultraviolet lasers can be used for ophthalmic surgery; and terahertz lasers ( Terahertz laser), which is also the study object of Sushil Kumar's research team of Associate Professor of School of Electronics and Computer Engineering at Lehigh University.
The picture shows terahertz photonics lab.
In the electromagnetic spectrum, the radiation emitted by the terahertz laser is located between the microwave and the infrared light. The radiation can penetrate common packaging materials such as plastics, fabrics and cardboards, as well as optical sensing of various chemical substances. The analysis is very effective. Such lasers (terahertz lasers) have broad application prospects and can be used for non-destructive screening and detection of packaged explosives and illicit drugs, assessment of pharmaceutical compounds, screening for skin cancer, and even for stars and Research on the formation of galaxies.
Applications such as spectroscopy require the laser to emit at a precise wavelength, which is usually achieved through a technique called 'distributed-feedback'. This device that emits accurate wavelengths is called a single-mode laser. (single-mode lasers) Since the most important applications of terahertz lasers will be in terahertz spectroscopy, the requirement for single-mode operation is particularly important for terahertz lasers. Currently, terahertz lasers are still in the development phase, research around the world. People are trying to improve their performance characteristics so that they meet commercial feasibility conditions.
Terahertz radiation is absorbed by atmospheric humidity during propagation. Therefore, the key requirement is that such lasers must be strong enough to be used for optical sensing and material analysis of several meters or more without being absorbed. Kumar's research team is focused on increasing the intensity and brightness of the laser, which can be achieved to some extent by increasing the optical power output.
According to the consulting report of Mymes, recently, the team of Lehigh University led by Kumar and Sandia National Laboratories has published a paper in the journal Nature Communications. The simple and effective technique of laser output power is 'surface-emitting' (this technology is very different from those using the 'edge-emitting' structure). In these two types of lasers, semiconductor lasers The surface emitting structure provides unique advantages for the commercialization of laser miniaturization, packaging and testing.
This published study describes a novel technique by which a specific type of periodicity can be introduced into the optical cavity of a laser to radiate a high-radiation-efficiency, high-quality beam fundamentally, thereby making the laser more powerful. In the research, the scheme was called 'hybrid second-and fourth-order Bragg grating' (which is different from the second-order Bragg grating of a typical surface-emitting laser. In nearly 30 years Various types of such lasers have been widely used. The researchers claim that their hybrid grating scheme is not limited to terahertz lasers, and that this scheme is likely to increase the wide range of surface emitting semiconductor lasers emitting at different wavelengths. Performance.
The study discussed the experimental results of a single-chip single-mode terahertz laser with a power output of 170 milliwatts. This is by far the most powerful laser of this class. Studies have shown that so-called hybrid gratings can Through the simple periodic variation of the imprinting grating in the laser cavity, the laser emits laser light of a specific wavelength while maintaining the beam quality. Kumar insists that their technology can continuously improve in the future and can achieve a power of 1 watt and above. Level, as long as this threshold is overcome, it can attract industry attention and gradually realize the terahertz laser instrument The potential commercialization.
