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58. Ultrafast Technology

Author

Anderson, Matthew E., primary, Thornes, Josh, additional, Poon, Phillip, additional, Resan, Bojan, additional, Archundia, Luis, additional, Delfyett, Peter J., additional, and Wise, Frank, additional

Published
2004
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68. Femtosecond laser nanosurgery of sub-cellular structures in HeLa cells by employing Third Harmonic Generation imaging modality as diagnostic tool.

Author

Tserevelakis, George J., Psycharakis, Stylianos, Resan, Bojan, Brunner, Felix, Gavgiotaki, Evagelia, Weingarten, Kurt, and Filippidis, George

Abstract

Femtosecond laser assisted nanosurgery of microscopic biological specimens is a relatively new technique which allows the selective disruption of sub-cellular structures without causing any undesirable damage to the surrounding regions. The targeted structures have to be stained in order to be clearly visualized for the nanosurgery procedure. However, the validation of the final nanosurgery result is difficult, since the targeted structure could be simply photobleached rather than selectively destroyed. This fact comprises a main drawback of this technique. In our study we employed a multimodal system which integrates non-linear imaging modalities with nanosurgery capabilities, for the selective disruption of sub-cellular structures in HeLa cancer cells. Third Harmonic Generation (THG) imaging modality was used as a tool for the identification of structures that were subjected to nanosurgery experiments. No staining of the biological samples was required, since THG is an intrinsic property of matter. Furthermore, cells' viability after nanosurgery processing was verified via Two Photon Excitation Fluorescence (TPEF) measurements. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Published
2012
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71. Frequency Noise Characterization of a 25-GHz Diode-Pumped Mode-Locked Laser With Indirect Carrier-Envelope Offset Noise Assessment

Author

Brochard, Pierre, Wittwer, Valentin Johannes, Bilicki, Slawomir, Resan, Bojan, Weingarten, Kurt John, Schilt, Stéphane, Südmeyer, Thomas, Brochard, Pierre, Wittwer, Valentin Johannes, Bilicki, Slawomir, Resan, Bojan, Weingarten, Kurt John, Schilt, Stéphane, and Südmeyer, Thomas

Abstract

We present a detailed frequency noise characterization of an ultrafast diode-pumped solid-state laser operating at 25-GHz repetition rate. The laser is based on the gain material Er:Yb:glass and operates at a wavelength of 1.55 μm. Using a beating measure-ment with an ultralow-noise continuous-wave laser in combination with a dedicated electrical scheme, we measured the frequency noise properties of an optical mode of the 25-GHz laser, of its repetition rate and indirectly of its carrier-envelope offset (CEO) signal without detecting the CEO frequency by the standard approach of nonlinear interferometry. We ob-served a strong anticorrelation between the frequency noise of the indirect CEO signal and of the repetition rate in our laser, leading to optical modes with a linewidth below 300 kHz in the free-running laser (at 100-ms integration time), much narrower than the individual contributions of the carrier envelope offset and repetition rate. We explain this behavior by the presence of a fixed point located close to the optical carrier in the laser spectrum for the dominant noise source.

75. Dispersion-managed Breathing-mode Semiconductor Mode-locked Ring Laser

Author

Resan, Bojan

Subjects
optics, lasers, mode-locked lasers, semiconductor lasers, ultrafast pulse generation, ultrafast technology, high power lasers, laser physics, Electromagnetics and Photonics, Optics
Abstract

A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short as 185 fs, with a peak power of ~230 w, and a focused intensity of ~4.6 gw/cm2 are generated by linear down chirp compensation and characterized by shg-frog method. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system. The very good agreement between the simulated and the measured results verifies our understanding and ability to control the physical mechanisms involved in the pulse shaping within the ring cavity. Application trends such as continuum generation via a photonic crystal fiber, two-photon fluorescence imaging, and ultrafast pulse source for pump-probe experiments are demonstrated.

Published
2004

76. Centre for Advanced Laser Techniques (CALT)

Author

Aumiler, Damir, Jovanovic, Igor, Resan, Bojan, Osvay, Károly, and Coslovich, Giacomo

Subjects
Laser Centre, EU Structural funds, laser techniques, laser infrastructure
Abstract

A research infrastructure centre - Centre for Advanced Laser Techniques (CALT) is going to be established at the Institute of Physics, Zagreb, Croatia. The available expertise of the Institute’s research staff and their high level of participation in collaborative research across Europe are the basis for the CALT project application (14 mil. €) to the European Regional Development Fund (ERDF). The project was preselected by the Ministry of Science, Education and Sports of the Republic of Croatia to receive financial support for preparing technical documentation, in order to be ready for applying to the ERDF for financing in the programming period 2014-2020. CALT will be located at the Institute of Physics in Zagreb (IPZg), the only research institution in Croatia to have several larger laser and optical systems. They are the basis for laser-matter interaction studies, including femtosecond pump-probe spectroscopy, frequency comb spectroscopy, ultra-cold matter, laser produced plasmas and plasma spectroscopy, holography and interferometry. These segments of the Institute’s infrastructure, together with the research and technical expertise of the Institute’s staff are unique on the national level. New research topics and equipment planned within CALT are therefore a natural extension of the already existing research activities at IPZg, aiming to establish a national research centre specialized in laser and optical techniques.

Published
2019

77. Ultrafast Transient Absorption of Adamantyl-Phenol

Author

Forjan, Mateo, Šekutor Marina, Basarić, Nikola, Vdović, Silvije, Jovanović, Igor, Resan, Bojan, Osvay, Károly, and Coslovich, Giacomo

Subjects
Physics::Optics, Physics::Chemical Physics, Femtosecond laser, CPA, transient absorption, photochemical reactions, conical intersection, quinonemethide, supercontinuum generation, third-harmonic generation
Abstract

Ultrafast dynamics of adamantyl-phenol was studied by measuring time-resolved absorption changes using transient absorption spectroscopy technique. Adamantyl-phenol molecules dissolved in acetonitrile-water mixture (1:1) were excited by femtosecond laser pulses with the wavelength of 267nm (pump pulse) while their absorption as a function of time was tested with the probe pulses. Probe pulse spectrum was supercontinuum generated in calcium-fluoride (CaF2) crystal pumped by 800nm. Resulting signal was positive, meaning the molecules have negligible fluorescence. After the excitation to first excited electronic state photochemical reaction of photodehydratation takes place and the formation of quinone methide (QM) begins via conical intersection. Quantum-chemical TD-DFT calculations indicate immediate ground state QM formation and the simulated ground state QM spectra is compared to measured one. Obtained results proved the functionality of the used experimental setup which will be used for future research and ultrafast transient absorption measurements of many different samples.

Published
2019

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