Peter Uhd Jepsen

 

We recently installed a new amplified femtosecond laser system in our labs, with funding from laserlab.dk. The system (Solstice Ace from SpectraPhysics) delivers 6 mJ pulses at a repetition rate of 1 kHz, with pulse length 100 or 35 femtoseconds. The system includes a high-energy optical parametric amplifier (HE-TOPAS from SpectraPhysics/LightConversion), and delivers a total of >3 mJ pulse energy in the near-infrared range. The laser system will primarily be used for nonlinear THz spectroscopy.

new_laser_small

 

Our group has an open PhD position in ultrafast nonlinear two-dimensional terahertz spectroscopy for experimental and theoretical investigation of nonlinear vibrational coupling and broadening mechanisms in the low-frequency phonon spectrum of molecular crystals. Firm knowledge about such interactions is highly relevant for the understanding of energy dissipation in molecular systems, and in a broader perspective, towards an understanding of the basic mechanisms underlying strong-field induced effects to living systems.

Deadline for application is November 8, 2015. See the full advertisement here.

 

On June 26th, the construction of a new laboratory wing for DTU Fotonik was officially initiated by the President of the Technical University of Denmark, Anders Bjarklev (right), and Department Head, Lars-Ulrik Aaen Andersen (left). The new building will host two new and greatly improved THz laboratories, with an area of 140 m2 (approx 1500 sqft). The construction will be completed in March 2016.

 

Ph.D. student Corinna Koch Dandolo participated in the recent LACONA X ((Lasers in Conservation, Sharjah, United Arab Emirates) conference and won the Best Poster Award for her work on Panels inspection behind gilded finishes through Terahertz Time-Domain Imaging (THz-TDI). This work is part of our efforts on using commercial-grade THz imaging equipment in the field for inspection of important art and cultural heritage artifacts.

You can download a copy of the poster here.

poster_award

 

On March 15, 2014, Mr. Abebe Tarakegne starts his Ph.D. project in our group. He will be working on extreme nonlinear optics of metals in the THz frequency range, an excited project involving high-intensity THz pulses, nanoplasmonics, field enhancement techniques, and light spanning the complete spectrum from THz to the UV.

 

Our Ph.D. student Corinna Koch Dandolo has recently visited Sicily for a very successful campaign where she investigated wooden statues and frescoes in a local church. Our portable THz imaging system was shipped there, and during the 10-day campaign, a wealth of depth-resolved THz images of a wide range of objects were acquired.

You can read more about the campaign here, at the Cultural Heritage Science Open Source blog:

Newly discovered frescoes

Wooden statues

 

Member of the THz Science and Technology crew, Pd.D. student Pernille Klarskov, has received a prestigious 300.000 DKK (50.000 USD) Award from the Danish Council for Independent research.

The Award will enable Pernille Klarskov to visit the group of Prof. X.-C. Zhang at the Institute of Optics, Rochester University, during 2014. During this research visit, Pernille will be investigating nonlinear interactions between intense THz waves and molecular crystals, as part of the HI-TERA project.

The Elite Research Travel Award was handed over to Pernille Klarskov by the Danish Minister for Research and Education at a ceremony in Copenhagen on February 6, 2014.

Read more about the EliteForsk Awards here (sorry, in Danish only).

A picture of the recipients of the travel Award together with HRH, Crown Princess Mary and the Minister of Research and Education, can be found here. Pernille Klarskov is No. 7 from the left.

 

Are you interested in a cool PhD project? We are looking for outstanding candidates for a three-year PhD project in our group at the Technical University of Denmark.

The project is about extreme nonlinear THz optics of metals. Check out the job posting at the DTU web pages.

Notice that the application procedure is strictly via the DTU online recruitment system. For technical questions, feel free to contact Professor Peter Uhd Jepsen (puje@fotonik.dtu.dk).

Deadline for the application is October 27th, 2013.

 

In a recent paper published in ACS Nano Letters, we report on the use of terahertz time-domain spectroscopy for contact-free measurement of the electrical conductivity of single-layer graphene.

In spite of the atomically thin structure, impressive progress towards large-scale fabrication of films of graphene with high contuctivity, high transparency to visible light, and high mechanical robustness. Graphene is therefore a strong candidate for next-generation touch-screen display technology and top electrode material in solar cells.

With the development of large-area graphene films (approaching square meters), there is a high demand for rapid screening technology for quality inspection of such films. Rapid screening requires contactless measurement technology, and this is where THz technology enters the picture.

Here we have demonstrated that a tightly focused beam of THz radiation can be used for rapid determination of the local electrical conductivity of single-layer graphene. The measurements have been carefully compared to another state-of-the-art conductivity characterization technology, namely micro-four point probes. 

The left panel of the Figure shows a THz-TDS based conductivity map of a single-layer graphene flake. The scale bar is 2 mm. The right panel shows the corresponding micro-four point probe map of the same flake.  

The report focuses on the close correlation between the THz-frequency measurements (AC conductivity) and the M4PP measurements (DC conductivity), and among other things, we demonstrate that THz-frequency measurements are sensitive to the nanoscopic conductivity while the M4PP technique is sensitive to the conductivity on the length scale of the pitch of the electrodes of the M4PP sampling head. This fundamental difference makes the two techniques complementary, and the combination of the two techniques is thus a unique characterization tool.

Together with the Nanointegration group at DTU Nanotech, we carried out the investigation in collaboration with researchers at McGill University, Montreal, Canada, and Chalmers University of Technology, Gothenburg, Sweden.

Citation: J. D. Buron, D. H. Petersen, P. Bøggild, D. G. Cooke, M. Hilke, J. Sun, E. Whiteway, P. F. Nielsen, O. Hansen, A. Yurgens, and P. U. Jepsen, “Graphene Conductance Uniformity Mapping,” Nano Lett. DOI: 10.1021/nl301551a (2012)

For additional information, please contact Prof. Peter Uhd Jepsen.

 

On September 3rd we were very happy to welcome the latest member of the THz crew, Ph.D. student Corinna Koch Dandolo. For the next three years, Corinna will be working on THz imaging for nondestructive analysis of cultural and art artifacts, in a project funded by DTU Fotonik and carried out in close collaboration with the Conservation Unit at the Danish National Museum.

© 2012 Terahertz.dk Our research is carried out at DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark. Suffusion theme by Sayontan Sinha