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ALT'23 The 30th International Conference on Advanced Laser Technologies
LD-O-12
Up-Conversion in CdSe/ZnS quantum dots in liquid-crystal matrices
N.D. Presnov1, V.Yu. Nesterov1, V.B. Zaytsev1, LAGolovan1, A.S. Merekalov2, Ya.I. Derikov2, O.N. Karpov12, G.A. Shandryuk12, R.V. Talroze12
1- Faculty of Physics, M.V.Lomonosov Moscow State University, Moscow 119991, Russia
2- A.V.Topchiev Institute of Petrochemical Synthesis RAS, Moscow 119991, Russia
Semiconductor quantum dots are of great interest for researchers and engineers due to their special properties, including high efficiency of photolumescence (PL). The idea to form QD nanocomposite media based on of liquid-crystal polymers (LCP) is very promising since they allow formation of ordered QD arrays, high QD concentration, and ability to control QD distribution by means of light-induced order-disorder transitions.
We report on up-conversion in core/shell CdSe/ZnS QDs embedded into smectic BA-6PA LCP with various QD mass fractions (up to 60%). QD diameter was 4.1 nm.
Under excitation of both QDs toluene suspension and QDs in LCP by femtosecond infrared pulses of Cr:for-sterite laser (1250 nm, 80 fs, 1 nJ, 80 MHz) visible PL was registered. The PL spectrum - a broad band 1.952.25 eV (550 - 640 nm) - coincides with one excited by picosecond pulses at wavelength of 532 nm. Analysis of the PL spectra reveals their saturating cubic dependence on the pumping laser power, which indicates three-photon absorption as a main mechanism of the up-conversion process.
This conclusion was supported by direct measurement of nonlinear absorption of femtosecond infrared pulses, which evidences square dependence of the absorption coefficient on laser power. Excitation of the PL (584 nm) can be done by the second harmonic (SH) of the femtosecond infrared radiation (625 nm), with the linear dependence of the PL on the SH power.
This work was supported by Russian Science Foundation (grant 23-19-00246), synthesis of QDs and polymer matrices was carried out within the State Program of TIPS RAS.
