| Abstract [eng] |
Expanding the range of semiconductor light sources into the infrared region has opened up broad application possibilities. Mid-infrared sources are particularly in demand, as many organic compounds in this range have characteristic energy absorption bands related to the rotational and vibrational motions of organic molecules. Tunable semiconductor infrared radiation sources are therefore well-suited for spectroscopic applications involving organic compounds. Coherent tunable light sources are especially sought after. Currently, quantum cascade lasers are the only type of coherent semiconductor radiation covering the entire spectrum of middle infrared radiation. Additionally, these sources are highly compact and exhibit a sufficiently wide tunability, further enhancing the attractiveness of these light sources in spectroscopic applications. One of the applications for these sources, which is being developed at the Center for Physical and Technological Sciences, is the control of polymerization processes. Particularly, this method is relevant for ensuring product quality in the furniture industry, printing, and food packaging production, where it is intended to be used for monitoring the completeness of UV radiation-induced polymerization processes. In this work, the principles of designing tunable quantum cascade laser active regions were studied, along with their growth technology using molecular beam epitaxy, and investigations of electrical and optical characteristics. FTMC-designed quantum cascade laser with a projected wavelength of 8,3 µm was grown using molecular beam epitaxy and shaped through photolithography. Additionally, the parameters of operating temperature and current on the emission spectrum of this laser was examined. Based on the studied properties, operating currents were selected to match emission spectra suitable for reference, which was 7,7 A corresponding to 8,12 μm wavelength, and main reflectance, which was 10,5 A corresponding to 8,36 μm. These signal measurements were used for controlling the completeness of furniture boards polymerization process. A measurement setup was assembled, and using the developed laser and selected operating parameters, the concept of measuring the completeness of UV curing of furniture boards was achieved. However, this system has a very narrow application scope. In order to explore the potential applications of the developed quantum cascade lasers in spectrometry, a system with tunable external 43 resonator in Quasi–Littrow configuration was created and its properties were investigated. The tunability of the system using diffraction grating was achieved from 8,12 µm to 8,38 µm with the wavelength shift depending on diffraction grating angle equal to 0.308 µm/arcmin. Using Quasi– Littrow configuration our laser achieved single mode emission with the width of 1 cm-1 . Unlike the electrically tunable system, this system allows for the continuous tuning of the laser emission wavelength and its application in spectrometry. |
