A report just released by a group of researchers at the School of Physics at the University of Warsaw about their use of micro-triplet devices to produce femtosecond laser pulses in the UV spectrum. The device is three times more efficient and fits fingertips than previous devices, a result of a unique software package developed in Warsaw during the design phase.

With the development of new technologies, lasers cover larger and larger spectra, but some wavelengths are still not easy to achieve. This includes an ultraviolet (UV) band of about 300 nanometers, especially if short pulse durations are to be achieved and high strength. In general, UV pulse generation is typically generated by nonlinear processes, such as second harmonic generation or sum frequency generation, where new photons have a higher energy by superposing the energy of the summed fundamental pulsed photons and have a new The color is formed. However, the efficiency of these processes is very low.

For years, analyzing light propagation models or simple numerical simulations was used to design frequency converters. They allow scientists to adjust equipment parameters, usually one at a time. This method has led to the amplification efficiency of infrared femtosecond laser to UV third harmonic has been very low, at about 10%.

"It's like in the lab, here's a knob, a knob to adjust it, looking at the UV output and trying to find the point where it's maximized, and 10 percent is the best result of one of these methods , "Said Michal Nejbauer, a researcher at the research group at the Warsaw University School of Physics.

But adding computational power combined with intelligent programming techniques allows the global optimization of the frequency conversion process from IR to UV conversion which is the first time this method has been used.

"Our newly developed, open source software package, called Light Cavalry, even lets an inexperienced user build a complex, stereoscopic, accurate simulation of the propagation and interaction of multiple pulses with simple blocks: inputting pulse parameters, The material properties and processes of the media can be realized, "explains Tomasz Kardas, who developed the software.

"Once we have defined the parameters of the input pulse such as the beam distribution in terms of energy, time and space, we basically start looking for the best design parameters in a large space: nonlinear crystal thickness, spot size, beam waist position, etc. To our surprise, once we found these best values, built the device and tested its performance, it was exactly the time to simulate the output of the light pulse, which was on a single screen and then in the lab Measured as a nonlinear optical very rare result. "

But increasing the efficiency of its conversion process by three times, to 30 percent or more, is just the first step. Researchers are also working on their miniaturization. Instead of using multiple components mounted on a bench, their triplet harmonic generator is just a tiny piece of crystal stacked together.

"In fact, a one-inch metal frame that brings all the elements together is the largest part of the setup," explains Pawel Wnuk, who led the performance experiments on the device. Therefore, the overall volume of the prototype of the frequency multiplier is approximately less than 1000 times that of the conventional design.

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