A team of researchers at the Warsaw University School of Physics has just released a report about their use of miniature triple frequency devices to generate femtosecond laser pulses in the ultraviolet spectrum. Compared with the previous device, the device has three times the efficiency and fits the size of the fingertip. This result is due to a unique software package developed by Warsaw during the design phase.
With the development of new technologies, laser pointer cover a larger and larger spectrum, but some wavelengths are still not easy to achieve. This includes the ultraviolet (UV) band of about 300 nanometers, especially if short pulse durations and high intensity are to be achieved. Normally, UV pulse generation is generally generated by a non-linear process, such as second harmonic generation or sum frequency generation, in which new photons have a higher energy and have a new energy by superimposing the sum of the energy of the basic pulse photons Color formation. However, the efficiency of these processes is very low.
For many years, analytical light propagation models or simple numerical simulations have been used to design frequency converters. They allow scientists to adjust equipment parameters, usually one at a time. This method has resulted in the conversion efficiency of the unamplified infrared femtosecond laser to the third harmonic of ultraviolet light has been very low, at about 10%.
It’s like in the laboratory, here a knob, there is a knob to adjust, while looking at the UV output power and trying to find its maximum point. 10% is the best result achieved by this method. He is currently a researcher in the research team of the Warsaw University School of Physics.
But intelligent programming techniques combined with increased computing power allow for a globally optimized frequency conversion process, from infrared to ultraviolet light conversion. This is the first time this method has been used.
“Our newly developed, open source software package, called Light Cavalry, even allows an inexperienced user to create a complex, three-dimensional, accurate simulation of the propagation and interaction of multiple pulses, using a simple block: input pulse parameters, The material properties and processes of the medium can be achieved” Tomasz Kardas explained that he developed this software.
“Once we have defined the parameters of the input pulse, such as energy, time, and spatial beam distribution, we basically start to look for the best design parameters in a large space: the thickness of the nonlinear crystal, the spot size, the beam waist position, etc. To our surprise, once we found these optimal values, built the device and tested the performance of the green laser pointer, the output light pulse was exactly what it was during simulation. This quantitative protocol is on a screen, and then What is measured in the laboratory becomes a very rare result in nonlinear optics.”
But increasing the efficiency of its conversion process has tripled to more than 30 percent, which is just the first step. The researchers are also committed to its miniaturization. Instead of using multiple components to install on the test bench, their triple frequency harmonic generator is just a small crystal stacked together.
“In fact, the one-inch metal frame that brings all the elements together is the largest part of the entire setup,” explained Pawel Wnuk, who led the implementation of the device’s characterization experiments. Therefore, the overall volume of the prototype of the frequency multiplier is about 1000 times less than the traditional design.