Ultrafast Dynamics Group

Ultrafast Dynamics Group

Group members:

Dr. Csaba Janáky (group leader, senior research fellow)

Dr. Viktor Chikán (senior research fellow)

Dr. Károly Mogyorósi (research fellow)

Dr. Gergely Samu (research fellow)

Krisztina Sárosi (early-stage researcher)

 

R&D activity

Ultrafast Dynamics Group probes ultrafast charge carrier dynamics at semiconductor interfaces and in nanoparticles and aims at controlling chemical and physical processes with light.

To probe ultrafast charge carrier dynamics at semiconductor interfaces we are developing novel tools which allow to carry out laser-driven spectroscopic experiments under electrochemical control. We are combining electrochemistry with different pump-probe techniques (e.g., time-resolved fluorescence, THz absorption, mid-IR). These methods will allow us to better understand the charge transfer processes at solid/solid and solid/liquid interfaces, thus accelerating solar energy research. Furthermore, the perturbation from the strong terahertz electric field will allow studying the dynamical properties of electrons in polarizable systems, like doped semiconductor quantum dots and metallic nanoparticles exhibiting electrons delocalized on several thousand atoms. Besides studying relaxation dynamics of charge carriers in the presence of strong optical bias, we aim at exploring fundamental steps needed to generate higher harmonic radiation from nanoparticles.

Another aim of the group is the control of chemical reactions and charge transfer utilizing terahertz light pulses in the condensed and the gas phase. Our group is interested in how the terahertz electric field can be efficiently used during the simplest chemical reactions so called photodissociation reactions initiated by intense XUV pulses: the high intensity, quasi static terahertz pulse will enable us to influence conical intersections based on the polarizability of the various excited states accessed during XUV photodissociation. We will investigate how tunneling reactions involving light fragments such as proton or electron can be significantly manipulated with the help of intense static electric fields.

 

     

 

  

Transient Absorption/Reflection Spectrometer (TAS) is an instrument for femtosecond pump-probe spectroscopy.  TAS incorporates highest quality optics, opto-mechanics, Fourier Transform spectrograph, optical chopper, vibration control, delay-line stage, and easy-to-use LabVIEW™ based software to deliver results. TAS can be upgraded and reconfigured to support many other ultrafast spectroscopy techniques as your research needs evolve.

 

  • Flexibly designed femtosecond pump-probe spectromete
  • Supports a variety of ultrafast laser present at ELI-ALPS
  • Broad pump-probe delay range and high pump-probe delay resolution
     

 

 

Sample types and conditions for TAS measurements

  • Transient absorption/reflectivity/anisotropy measurements with up to 8 fs time resolution
  • Solid and liquid sample handling
  • Wide range of in situ temperature measurements (-40 °C-105 °C)
  • In situ electrochemical control(bias) and measurements (CV, conductivity etc.) in a custom-made electrochemical cell to measure generation and annihilation of charge carriers in the electrode material
  • Single beam and double beam referencing mode

 

     

 

  

Available Light Sources:

 

  • Technical specification with HR laser
    • Pump: Same as HR laser (100 kHz, 1030 nm/515 nm)
    • Probes: white light (CaF2, Sapphire and LiF), terahertz probe (ZnTe: 0-3 THz GaP: 1-7 THz, 2 color laser induced plasma: 1-40 THz),
    • Time resolution: ~6-10 fs
  • Technical specification with SYLOS laser
    • Pump: (1 kHz, 908 nm/454 nm)+THz pump (~150 kV/cm, @~1 THz)
    • Probes: white light (CaF2, Sapphire and LiF), terahertz probe (ZnTe: 0-3 THz GaP: 1-7 THz, 2 color laser induced plasma: 1-40 THz),
    • Time resolution:  ~6 fs
  • Technical specification with Terahertz pump laser
    • Pump: (1 kHz, 908 nm/515 nm)+THz pump(~150 kV/cm, @~1 THz)
    • Probes: white light (CaF2, Sapphire and LiF), terahertz probe (ZnTe: 0-3 THz GaP: 1-7 THz, 2 color laser induced plasma: 1-40 THz),
    • Time resolution: ~6 fs
   

 

 

Reaction Chamber for gas phase pump (XUV/DUV/UV/IR/Terahertz) and Chemiluminescence (UV/VIS/NIR/IR) probe experimental setup is capable of studying photodissociation processes and chemical reaction between radicals in the gas phase. The chemiluminescence spectrum is detected by a Fourier Transform Spectrometer capable of operating in step scan mode to obtain time-resolved spectra.

 

  • Ideally suited for detecting fluorescence fragments
  • Can be combined with ion detection schemes
  • Plasma diagnostics and LIBS measurements
  • Fourier Transform Visible to MIR Spectrometer: Bruker Vertex 80: spectral range: 50000-600 cm-1, step scan capable, time resolution: 2.5 ns, synchronizable with 100 kHz or 1 KHz laser system, spectral resolution: 0.06 cm-1

 

Publications

R. Flender, A. Börzsönyi, V. Chikán

Phase-controlled, second harmonic optimized THz pulse generation in nitrogen by infrared two-color laser pulses

J. Opt. Soc. Am. B

link

 

K. Mogyorósi, K. Sárosi, I. Seres, P. Jójárt, M. Füle, and V. Chikán

Formation of CN Radical from Nitrogen and Carbon Condensation and from Photodissociation in Femtosecond Laser-Induced Plasmas: Time-Resolved FT-UV−Vis Spectroscopic Study of the Violet Emission of CN Radical

J. Phys. Chem. A, 124, 2755−2767, 2020

link

 

R. Flender, K. Sárosi, E. Petrács, A. Börzsönyi, V. Chikán

Controlling terahertz spectrum in asymmetric air plasmas: the role of GDD and phase

Proc. SPIE 10684, Nonlinear Optics and its Applications 2018, 1068428

link 

 

R. A. Scheidt, G. F. Samu, Cs. Janáky and P. V. Kamat

Modulation of Charge Recombination in CsPbBr3 Perovskite Films with Electrochemical Bias

J. Am. Chem. Soc., 140, 86--89, 2018

link

 

Gergely F. Samu, Rebecca A. Scheidt, Prashant V. Kamat , Csaba Janáky

Electrochemistry and Spectroelectrochemistry of Lead Halide Perovskite Films: Materials Science Aspects and Boundary Conditions    

Chemistry of Materials

link

 

R. Flender; K. Sárosi; A. Börzsönyi; V. Chikán

The impact of dispersion of the ultrashort light pulses on the THz radiation formation from asymmetric air plasmas

Proc. SPIE 10228, Nonlinear Optics and Applications 2017, 102281B

link

 

October

24

Sunday