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Development of a compact tunable fiber laser
A team of researchers from the U.S. developed a compact laser system that enables a tunable fiber laser over a wide range. The fiber laser is made from commercial-off-the-shelf components and is designed to emit terahertz radiation by spinning the energy levels of molecules in nitrous oxide (laughing gas).
The tunable fiber lasers provide new data information from the novel computational techniques. This gas laser technology was regarded as old for a long time; therefore, researchers thought that the laser systems were big, low-power, and non-tunable, which is why terahertz sources are considered to be potential.
Compact size and efficiency
Modern tunable fiber lasers have a compact size, can be tuned, and offer more efficiency parameters. Additionally, it is possible to put this fiber laser system in one’s backpack or vehicle for wireless communications or high-resolution imaging. The design of the tunable fiber laser is based on the research done in the 1980s, according to which a gas laser system allows emitting terahertz laser beam waves; the fiber laser is smaller than conventional laser devices, and at a pressure far higher than the theoretical models of the time suggested.
Vibrational states and laser performance
Manufacturers of those fiber laser models did not pay attention to several vibrational states, “assuming that only a handful of vibrations were what ultimately mattered in producing a terahertz wave”. According to the previous models, if a cavity is tiny, molecules vibrating in response to an incoming infrared laser system will collide more often and produce their energy rather than building it up further to spin and emit terahertz waves.
Tracking molecular states
The new fiber laser model enables us to track thousands of relevant vibrational and rotational states among millions of groups of molecules within a single cavity. Then the laser technology performs an analysis of how those molecules respond to the incoming infrared laser beam, depending on their position and direction within the cavity. The researchers succeeded in discovering that the inclusion of all these other vibrational states in tunable fiber lasers (previously ignored by people) leads to the appearance of a buffer.
Quantum cascade laser as the infrared source
For the new model, a quantum cascade laser system has been chosen as the infrared laser beam source. The opportunity to change the frequency of the input fiber laser by turning a dial may change the frequency of the terahertz coming out. Several gas libraries were looked through by researchers in order to detect those that were known to rotate in a specific way in response to an infrared laser beam, finally deciding on nitrous oxide.
Prospects and gas molecules
The stimulation of the quantum cascade laser system results in the creation of a tunable fiber laser at a much smaller size than previously considered possible. Researchers include other gas molecules, for example, carbon monoxide and ammonia, offering a menu of various terahertz generation options with different frequencies and tuning ranges, paired with a quantum cascade laser system.