Фемтосекундное излучение

Фемтосекундное излучение     One of the important research directions of the laboratory is the study of non-linear processes regarding modifications of optical materials under the exposure to optical radiation, creation and investigation of periodic structures and waveguide structures in optical materials. For these purposes a universal experimental multifunctional complex setup based on a femtosecond laser with a radiation wavelength of 1035 and its second harmonic of 517.5 nm was created in the laboratory. The setup is equipped with high-precision translators and a vibration isolation system for the formation of structures with submicron resolution.

    To study nonlinear processes in glass and thin coatings, it is necessary to ensure a high intensity of laser radiation while keeping thermal exposure at the minimal level. For these purposes, laser radiation with a femtosecond pulse duration is used. Ultrashort pulses provide non-linear interaction with materials and, due to the low average radiation power, do not heat the sample. In addition, short pulses of laser radiation make it possible to investigate fast and ultrafast processes both during and after the removal of radiation. This principle underlies the well-known experimental Pump & Probe technique, as well as the principle of studying the nonlinear properties of Z-scan materials.

    The nonlinear interaction with optical materials (e.g., silica glasses) makes it possible to modify its properties by changing the refractive index via a nonlinear exposure to visible and infrared radiation. This technology underlies the creation of planar waveguides, a number of passive optoelectronic devices and periodic structures. For instance, by means of femtosecond inscription technology it is possible to create fiber Bragg gratings inscribed in non-photosensitive optical fibers with undoped silica core. Such Bragg gratings can be used as high-temperature and radiation-resistant sensor elements for the needs of the nuclear and aerospace industries.