Seminarium z fizyki biologicznej i bioinformatyki

link do spotkania: https://zoom.us/j/91976153012?pwd=azNiMWE4UnhPN3lRQlY2UHZHOXVkQT09

ABSTRACTPhoton avalanche (PA) is a highly nonlinear optical phenomenon firstdiscovered in 1979, originally investigated in bulk crystals at cryogenic temperatures for mid-infrared photon detection and upconversion lasers. It is initiated when photon absorption triggers a cascade of excited-state absorption (ESA) and energy transfer processes, forming a positive feedback loop that rapidly amplifies emission. A defining feature of PA is a sharp excitation power threshold, above which the luminescence intensity increases dramatically. Beyond this threshold, the emission intensity (IE) follows a power-law dependence on excitation power (IP), IE=(IP)^S,with an exceptionally large nonlinearity index S exceeding 10 and sometimes reaching several hundred. The process exhibits efficient anti-Stokes emission and a characteristic S-shaped dependence of emission intensity on excitation power density [1]. Achieving PA requires stringent conditions, including resonant ESA between excited states and an ESA cross section much larger than ground-state absorption. Equally critical is efficient cross-relaxation between lanthanide ions, which multiplies the population of intermediate states and sustains the avalanche process. Recentdemonstrations of PA in nano- and micro-scale materials, particularlyTm^3+-doped low-phonon hosts, have opened new opportunities for ultrasensitive sensing and advanced photonic technologies. During the talk, the basics of PA will be presented, likewise the novel concepts and demonstrations of superresolution imaging [2,3,4], and ultrasensitizesensing [1,5,6]. Some new directions and challenges will be indicated towards better (lower threshold, controlled non-linearity) PA nano & micro particles and layers.References 1. M. Szalkowski, A. Kotulska, M. Dudek, Z. Korczak, M. Majak, Ł.Marciniak, M. Misiak, K. Prorok, A. Skripka, P. J. Schuck, E. M. Chan, A.Bednarkiewicz, et al.,Chem. Soc. Rev. 54, 983 (2025). 2. Artur Bednarkiewicz, Emory M.-Y. Chan, Agata M. Kotulska, ŁukaszMarciniak, Katarzyna Prorok, et al., Nanoscale Horiz. 4, 706 (2019). 3. Lee, E. Xu, Y. Liu, A. Teitelboim, K. Yao, A. Fernandez-Bravo, A. Kotulska, S. H. Nam, Y. D. Suh, A. Bednarkiewicz, B. E. Cohen, E. M. Chan, P. J. Schuck, et al., Nature 592, 554 (2021). 4. S. Karmegam, M. Szalkowski, M. Misiak, K. Prorok, D. Szymański,A. Bednarkiewicz, et al., arXiv:2507.14667 (2025). 5. Bednarkiewicz, E. M. Chan, K. Prorok, et al., Nanoscale Adv. 2, 4863 (2020). 6. M. Majak, M. Misiak, A. Bednarkiewicz, et al., Mater. Horiz. 11, 4791 (2024).