Higher-order Kerr effect and harmonic cascading in gases


A new publication investigates the possible contribution of cascaded harmonic generation to the higher-order Kerr nonlinearities recently observed in gases. This contribution adds to a particularly heated debate at the moment about whether the higher-order Kerr effect plays a role in filamentation dynamics in gas cells.


Few-cycle mid-IR pulses generated with cascaded nonlinearities


At the Ultafast Phenomena conference in Lausanne, Switzerland, we presented the contribution Generating Few-cycle Energetic Mid-IR Pulses with Soliton Compression by Cascaded Quadratic Nonlinearities 


Cascaded compression reveals a new paradigm of ultrafast cascaded nonlinearities


A new method for compressing laser pulses overcomes power constraints that hamper current compressor technology. The method suggests a paradigm shift in ultrafast cascaded nonlinearities as for the first time octave-spanning bandwidth is achieved using the largest nonlinear components of conventional frequency conversion crystals. The utility of this process was confirmed experimentally by compressing energetic (sub-mJ) near-IR femtosecond pulses to four periods in the time domain. This happened in a just 1 mm long nonlinear crystal.


B. B. Zhou, A. Chong, F. W. Wise and M. Bache
Ultrafast and octave-spanning optical nonlinearities from strongly phase-mismatched cascaded interaction
Physical Review Letters 109, 043902 (2012)
doi, arXiv:1109.4261, Physics Synopsis


Efficient generation of few-cycle mid-infrared pulses


We show that energetic mid-IR few-cycle pulses can be generated when solitons shed optical Cherenkov radiation in ultrafast cascaded second-harmonic generation. The results were presented at NLO 2011, and has been published for the special issue in OE.


New project targets generation of mid-IR ultrashort laserpulses


A new research project has been granted to the Ultrafast Nonlinear Optics group. The project title is Femto-midIR: Femtosecond few-cycle mid-infrared laser pulses, and it is a 3-year Research Project funded by the Danish Council Independent Research | Technology and Production Sciences. The project will start in the summer 2012. The goal of the project is to use cascaded nonlinearities for generating few-cycle mid-IR pulses. 


Experimental proof of ultrafast noncritical SHG


Our recent experimental efforts have demonstrated sub-20 fs near-infrared pulses can be generated through soliton compression of energetic femtosecond pulses. The compression relies on noncritical cascaded type-0 second-harmonic generation in a just 1 mm long lithium niobate crystal. The results were presented at CLEO Europe 2011, and a journal paper was recently submitted.


B.B. Zhou, A. Chong, F.W. Wise and M. Bache
Ultrafast noncritical cascaded second-harmonic generation: Few-cycle soliton formation in short bulk nonlinear crystals without quasi-phase matching
submitted,  arXiv:1109.4261


B.B. Zhou, A. Chong, F.W. Wise and M. Bache
Sub-20 fs energetic near-IR pulses generated with cascaded soliton compression in short lithium niobate crystals
paper CF1.6, 2011 European Conference on Lasers and Electro-Optics and 12th European Quantum Electronics Conference 2011, Munich, Germany (2011). ISBN: 978-1-4577-0532-8. IEEE Catalog Number: CFP11ECL-ART


New PhD student started


In July 2011 Hairun Guo from China started a 3-year PhD in our group titled Cascaded quadratic soliton compression in waveguide structures.


Marie Curie fellow Xianglong Zeng started


In May 2011 Dr. Xianglong Zeng from Shanghai University started his Marie Curie IIF, COPULCO: Cascaded Optical Pulse Compressor. He will stay 2 years at DTU Fotonik.


Optical Cherenkov waves in cascaded SHG: new PRA


We have published a paper in the December 2010 issue of PRA, where soliton-induced optical Cherenkov waves (aka. dispersive waves) are investigated in cascaded second-harmonic generation (SHG). The Cherenkov waves are found at longer wavelengths than the soliton due to the unique properties of cascaded SHG, and the resonance condition for a range of nonlinear crystals is shown.


New paper published in Physical Review A


In the May 2010 issue we investigate the potential of using lithium niobate as nonlinear crystal for generating cascaded femtosecond solitons and achieving soliton compression of pulses from commercial femtosecond fiber laser amplifiers. The results are an important step towards realizing sub-100 fs pulses from fiber laser amplifiers. Read more here.


New laboratory inaugurated


In April 2010 our new amazing lab was finally inaugurated. The Danish Minister of Economy Brian Mikkelsen made a speech and "cut" the stream-of-photons ribbon. Read more here.


2010 CLEO/QELS conference contribution


In the CLEO/QELS 2010 conference in San Jose we will present an oral contribution. Its title is Generating energetic few-cycle pulses at 800 nm using soliton compression with type 0 cascaded quadratic interaction in lithium niobate. See more information under Publications.


Marie Curie proposal accepted


A Marie Curie proposal has been accepted with Dr. Xianglong Zeng as fellow and Dr. Morten Bache as scientist in charge. The project will start later in 2010, and will focus on compression experiments with quasi-phase matched quadratic nonlinear crystals. Another Marie Curie is on the waiting list. Read more here.


New postdoc Binbin Zhou started


1 August 2009 the first new person on the Femto-VINIR project started. Binbin Zhou is now a postdoctoral associate, and will work on pulse compression experiments in our new lab. Read more here.


2009 CLEO Europe/EQEC conference contribution


In the CLEO Europe 2009 conference in Munich we presented an oral contribution. Its title was Dispersive waves in fs cascaded second-harmonic generation. The abstract reads:

Dispersive waves are observed in simulations of cascaded (phase-mismatched) second-harmonic generation. When generating ultra-short fs compressed near-IR solitons the dispersive waves are strongly red-shifted, depending on the soliton wavelength. Semi-analytical calculations predict the wavelengths.


See more information under Publications.


New paper published


In the newest volume of Journal of the Optical Society of America B, the potential compression performance of polymer microstructured optical fibers with quadratic nonlinear response is investigated. It was found that fine-tuning the dispersion profile using the microstructure of the optical fiber has less impact on the potential compression performance than the sheer size of the quadratic nonlinear response of the polymer. This result will have strong impact on other soliton systems based on cascaded quadratic nonlinearities (bulk crystals and waveguides). Click here to access the paper.




DFF Young Elite Researchers Award 2009 given to Morten Bache


Morten Bache has received the prestigious DFF “Young Elite Researchers Award” 2009. Read more here.



News release: New method will make it easier to generate extremely short laser pulses


In a new research project researchers aim to find more efficient methods for generating extremely short femtosecond laser pulses in the important visible and near-infrared regimes. These pulses can today only be generated in research laboratories with bulky, fickle state-of-the-art lasers operating complex setups. Read more here.