MIL OSI Translation. Region: Russian Federation –
Source: Novosibirsk State University – Novosibirsk State University –
Researchers of the joint Laboratory of Quantum Optical Technologies Faculty of Physics, Novosibirsk State University and the Institute of Laser Physics SB RAS (IPL SB RAS) are investigating the nonlinear optical properties of nonlinear crystals of ternary and quaternary barium chalcogenides BaGa4S7, BaGa4Se7, BaGa2GeS6 and BaGa2GeSe6. The results of these studies can be used to develop mid-IR radiation sources and gas analytical systems based on them. They will also be important in the design and development of efficient parametric light generators that generate radiation tunable in the spectral range of 3-15 μm, and laser optical-acoustic gas analyzers based on them. These devices are used to measure the concentration of volatile metabolites in the air exhaled by patients when diagnosing bronchopulmonary diseases. The introduction of such systems into medical practice will make it possible to identify these pathologies in the early stages, when the patient’s likelihood of recovery is still high.
— The crystals that are the object of our research were first grown from 2010 to 2016 at Kuban State University and the Institute of Geology and Mineralogy SB RAS. According to a number of characteristics, all four crystals under study have proven themselves to be promising media for parametric frequency conversion in the mid-IR range, in particular, in terms of transmission ranges, radiation resistance and effective nonlinearity coefficients. Previously, when implementing RSF projects, we have already studied some of the properties of these crystals, including radiation resistance. Therefore, we are now studying their nonlinear optical characteristics. It is important to take them into account when developing frequency conversion devices to achieve high output characteristics: high pulse energy and conversion efficiency in these crystals,” explained Nadezhda Kostyukova, a senior researcher at the joint Laboratory of Quantum Optical Technologies of NSU and the Institute of Physics of the Siberian Branch of the Russian Academy of Sciences, Candidate of Physical and Mathematical Sciences.
Nonlinear absorption and nonlinear refraction that arise in crystals when interacting with high-power laser radiation can lead to distortion of the transverse intensity distribution of the laser beam in the crystal, the manifestation of self-focusing effects and mismatch of the optical cavity. As a result, the efficiency of the parametric transformation decreases. Therefore, information about their magnitude must be taken into account when designing optical circuits of highly efficient parametric light oscillators (POLOs) tunable in the mid-IR range, which are widely used to solve various problems. For example, in spectroscopy (including optical-acoustic), gas analysis (including medical diagnostics), environmental monitoring and control of industrial emissions. These same radiation sources can be used to study the dispersion properties of materials, in laser surgery, as well as for various laboratory studies.
— We had to overcome some technical difficulties. We have not conducted such studies before. First, it was necessary to understand the technical part, and also find out what physical phenomena underlie the processes under study. It was necessary to take into account many nuances and select the optimal parameters of the experimental setup: the required thickness of the plates of the materials under study, optimal focusing, length of movement, and much more. A lot of time was spent on comparing theoretical data with the results obtained during the study. We made conclusions about the predominance of thermal effects in the samples under study when exposed to pulsed radiation with pulse repetition rates greater than 1 kHz and began to study them in detail,” said Evgeniy Erushin, junior researcher at the joint Laboratory of Quantum Optical Technologies of NSU and the Institute of Physics of the Siberian Branch of the Russian Academy of Sciences.
As a result of the experiment, scientists discovered that nonlinear absorption and nonlinear refraction in the crystal under study strongly depends on the average radiation power, which in our case is determined by the pulse repetition rate. At pulse repetition rates of more than 1 kHz, the heat between pulses does not have time to dissipate, the material begins to heat up locally, and the effects of nonlinear absorption and refraction become more pronounced. Accordingly, when exposed to radiation with a pulse repetition rate of more than 1 kHz, taking into account these effects becomes even more important for constructing efficient optical devices and extending their service life.
In order for scientists to make a correct comparison of characteristics, all four crystals of barium chalcogenides must be studied under the same conditions. Many characteristics strongly depend on the duration of the laser pulses. The researchers decided to use two lasers, pulsed and continuous. Currently, crystals have been studied using continuous radiation and nanosecond pulses. In the near future, studies will be carried out on the nonlinear optical characteristics of crystals when exposed to pulses with a picosecond duration.
— The results of our work can become a good foundation in the field of modern nonlinear photonics. Previously, systematic studies of nonlinear absorption and refraction of barium chalcogenide crystals have not been carried out, said Nadezhda Kostyukova.
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Please note; This information is raw content directly from the information source. It is accurate to what the source is stating and does not reflect the position of MIL-OSI or its clients.
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