Burning coal with femtosecond laser pulses 

 

Since before the industrial age, graphite materials have played an essential role in daily life: their properties are seen in everything from burning embers to the first electric bulbs. Even as technologies advance, graphite materials continue to pique interest in the human mind. 

One example is graphene, a two-dimensional material with remarkable optical and electronic properties, which has sparked a renewed interest in the field of semiconductor research, particularly in studies of solar energy conversion. Prof. Hrvoje Petek and his research group at the University of Pittsburgh are studying graphene to understand its hot electron dynamics. 

The researchers are particularly interested in how this material can be used to enhance the solar energy conversion process. With the help of Clark-MXR’s IMPULSE fiber laser, equipped with iNOPA, they were able to identify the fundamental properties of graphene and study the utility of the material in several applications. This research has produced two publications thus far, which appeared in Physical Review (DOI: 10.1103/PhysRevX.7.011004) and the Journal of the American Chemical Society (DOI: 10.1021/jacs.7b01079).

Progress of industrial femtosecond machining
A rich 20-year history  

Micromachining with femtosecond lasers (also known as ultrafast or ultra-short pulse lasers) is gaining popularity due to several advantageous properties, including the nearly athermal, or "cold," ablation process. For industries demanding smaller and more precise parts, this technology offers several benefits, including higher yields, tighter tolerances, little to no collateral damage, and no post processing.

While femtosecond lasers have begun gaining significant attention in recent years, they were originally showcased 20 years ago at the Laser World of Photonics in Munich, Germany by Clark-MXR, a company founded in 1992 in Dexter, MI. With the help of few other collaborators, Clark-MXR presented the first live demonstration of industrial femtosecond laser micromachining during an exposition or conference.

The image above depicts a glass slide machined with femtosecond laser pulses from a CPA-Series laser from Clark-MXR. These proof-of-principal parts were machined in real time during the show in Munich and given to attendees for them to take home.

Since this pioneering feat at the 1997 Laser World of Photonics, Clark-MXR has remained a key player in femtosecond laser micromachining, continuing to develop innovative processes and equipment, as well as providing femtosecond laser-based micromachining services to numerous industries.

Please join Clark-MXR at Laser World of Photonics in Munich, booth B2-207, to celebrate the success and the 20th anniversary of commercial femtosecond laser-based micromachining.

Catching molecules in the act 

Chemical reactions are characterized by the motion of atoms; transformation of chemical compounds, reactants, and raw materials is therefore governed by molecular vibrations. While the motion of the atoms is easily seen at the beginning and end of a chemical reaction, the molecular changes occur too rapidly in the middle of the process, making them impossible for humans to observe.

With novel techniques that employ the use of ultrafast lasers, however, we can essentially freeze the chemical reaction. This allows us to thoroughly observe the intermediate steps of the chemical reaction that were previously incomprehensible, even permitting control of these reactions. Surface Enhanced Femtosecond stimulated Raman Spectroscopy (SE-FSRS) is one such technique: with SE-FSRS, we are able to study chemical bond-breaking and formation at the femtosecond timescale. (Some perspective: one femtosecond is one millionth of one billionth of a second.)

The research group of Professor Richard Van Duyne at Northwestern University utilized and improved upon the SE-FSRS technique in this study of chemical reaction dynamics. In this research, the experiments were performed at 1 MHz repetition rate using the IMPULSE laser from Clark-MXR, Inc., the first time that the SE-FSRS technique has been used with a laser source running at this repetition rate. The researchers found that the 1 MHz system resulted in several advantages when compared to previous implementations that used lower repetition rate lasers: the 1 MHz system allowed for a lower pulse energy and a minimized sample exposure time, leading to less sample degradation and increased signal to noise. The success of this research has established SE-FSRS as a robust tool for studying molecular dynamics, opening the door to several other potential applications of the technology. 

In their next endeavor, the researchers at Northwestern University are planning to perform time-dependent studies, which will allow them to effectively catch the molecules in their act. 

More information: The original article: Surface-Enhanced Femtosecond Stimulated Raman Spectroscopy at 1 MHz Repetition Rates. Lauren E. Buchanan, Natalie L. Gruenke, Michael O. McAnally, Bogdan Negru, Hannah E. Mayhew, Vartkess A. Apkarian, George C. Schatz and Richard P. Van Duyne.  Appers in J. Phys. Chem. Lett. 2016, 7, 4629−4634 (DOI: 10.1021/acs.jpclett.6b02175)

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Synchronization of a 25 MHz Magellan Yb-doped Fiber Oscillator with a Streak Camera from Optronis       Clark-MXR, Inc. is pleased to announce the first demonstration of a Yb-doped femtosecond fiber oscillator running at 25 MHz successfully synchronized with a Streak camera. This is a result from a collaboration with the companies Optronis GmbH (Dr. Patrick Summ, summ@optronis.com) and Horiba Scientific GmbH (Dr. Hans-Erik Swoboda hans-erik.swoboda@horiba.com) from Europe. The Magellan is a telecom-qualified single emitter diode-pumped Yb-doped femtosecond fiber oscillator. A Streak camera from Optronis, Optoscope SC10, with Synchroscan sweep unit was triggered by the Magellan oscillator and different triggering set-ups were tested for best synchronization conditions and temporal resolutions.   This will open up a whole new research area that was unavailable until now to synchronize Yb-doped fiber oscillators with streak cameras at lower repetition rates. Experiments such as direct fluorescence lifetime measurements with high temporal resolution can now be implemented.

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