Mid- infrared ultrafast pulses are of interest in different applications ranging from vibrational spectroscopy, strong field physics (stable CEP) to detection of trace quantities of compounds. The traditional approach uses solid state lasers, i.e. mature but sensitive technology that is restricted to laboratory use due to its complexity. In real-world applications, ultrashort fiber lasers offer a more rugged, portable and scalable platform for the generation of tunable, brilliant mid-IR femtosecond pulses. This paper will cover approaches for the generation of high-intensity femtosecond pulses in the mid-IR region by means of DFG. The DFG technique also opens up new avenues for frequency comb applications and tunable absolute optical frequency sources. It can be used to set up intrinsically phase stable amplified laser systems as well. The power scalability of lasers with doped Thulium fibers made it possible to generate supercontinua in the mid-IR. Our mid-IR sources along with the availability of high power fiber optics, double clad doped gain fibers and LMA fibers for the 2μm and 1μm region enables "all fiber" compact and robust sources that can be man-portable.

Over past three decades ultrafast lasers have come a long way from the bulky, demanding and very sensitive scientific research projects to widely available commercial products. For the majority of this period the titanium-sapphire-based ultrafast systems were the workhorse for scientific and emerging industrial and biomedical applications. However the complexity and intrinsic bulkiness of solid state lasers have prevented even larger penetration into wider array of practical applications. With emergence of femtosecond fiber lasers, based primarily on Er-doped and Yb-doped fibers that provide compact, inexpensive and dependable fs and ps pulses, new practical applications have become a reality. The overview of current state of the art ultrafast fiber sources, their basic principles and most prominent applications will be presented, including micromachining and biomedical implementations (ophthalmology) on one end of the pulse energy spectrum and 3D lithography and THz applications on the other.

We demonstrate for the first time active dispersion and amplitude correction in a fiber laser producing sub-45 fs pulses. The approach is based on single-shot second and third order dispersion measurement based on multiphoton intrapulse interference. The same principle is applied to obtain time-resolved measurements of the transient dispersion induced by an intense laser pulse on a silica window.

We report precise characterization and compensation of high-order phase distortions of a supercontinuum generated by ultrafast fiber lasers. By using multiphoton intrapulse interference phase scan (MIIPS) technique, the pulses are compressed to 12.8 fs (within 0.1% of the transform-limited value) automatically in less than thirty seconds.

Detection and identification of chemical warfare simulants based on multidimensional phase shaped femtosecond laser pulses coupled to mass spectrometry (MS) is demonstrated. The presented approach is based on binary phase shaping (BPS) and aims to improve the accuracy and precision required for security applications. It is based on multiphoton intrapulse interference of femtosecond laser pulses. Spectra retrieved by applying n-differently shaped pulses represent n-dimensions of the analysis. We present a multidimensional technique for detection and identification of analogues to chemical agents and mixtures in real-time. Experimental results for dimethyl phosphate, pyridine, and three isomers of nitrotoluene are presented.

Breakthrough technology in remote femtosecond pulse characterization and accurate delivery of ultrashort shaped pulses to distances greater than 30 meters is being used to develop remote detection of explosives as well as biological warfare agents.

Based on nonlinear optics, multiphoton intrapulse-interference phase scan (MIIPS) provides high-accuracy pulse characterization without interferometry. Once distortions are measured, they are removed.

Phase-shaped femtosecond laser pulses and mass spectrometry were implemented as a tool for improving molecular identification. We demonstrate that the specific lines in the mass spectra of several chemical warfare simulants are sensitive to the phase characteristics of the incident laser field. The deviation in the relative yield of fragment ions observed upon pulse shaping (enhancement or suppression) adds a new dimension to mass spectrometry that improves molecular identification and can be used to quantitatively analyze mixtures of isomers.

Due to their ultrashort pulse duration and efficiency at inducing nonlinear optical processes, femtosecond lasers are now widely applied in chemical, physical, biological, and medical research. If recent patent activity is an indication, they will become the cornerstone of several applications, such as micromachining, metrology, and surgery. Unlike other laser systems, femtosecond lasers are sensitive to the frequency dependence of the group velocity of light when propagating through any medium. Therefore, applications requiring femtosecond lasers depend on accurate compensation of dispersion effects. Industrial, as well as clinical, applications require that all lasers consistently deliver identical pulses to the target to ensure reproducibility. Pulse characterization and automated compensation make this possible. The duration of an ultrashort laser pulse—only a few optical cycles in length—is limited by its bandwidth and the degree to which all its frequencies are in phase. The generation of such bandwidth-limited pulses depends on how accurately phase distortions, caused inside and outside the laser, can be measured and corrected. A new method, based on a programmable pulse shaper, is changing the decades-old autocorrelation paradigm and providing highaccuracy pulse characterization without interferometry. 2, 3 Analogous to the Wheatstone Bridge in electronics (which measures an unknown resistance by comparing it to known resistances), a calibrated phase function is used to directly measure the unknown phase distortions. Once measured, these distortions are removed. The entire handsoff process yields bandwidth-limited pulses within seconds and without moving parts. This new development responds to the needs of an increasing number of industrial and clinical applications of femtosecond laser systems.

Laser-based molecular identification has reached a new level of performance allowing real-time identification and quantification of mixtures containing isomers and enantiomers. The ROC curves of this method for absolute molecular identification will be discussed.

Polarization and phase shaped pulses can now be used for the absolute identification and quantification of mixtures containing isomers and enantiomers. The performance of this methodology will be discussed.

Spectral phase correction (TBP<1.005) of femtosecond regeneratively amplified pulses using a MIIPS-enabled pulse shaper positioned between the oscillator and amplifier is performed. Rigorous characterization of the shaped output pulses will be presented.

We report on the remote characterization and dispersion compensation (pulse compression) of femtosecond pluses using multiphoton intrapulse interference phase scan (MIIPS). The results presented here were carried out at a distance of 28.9 m from the target. The method could be used with targets placed kilometers away. The amplified pulses arrive at the remote target within one percent of transform limit or accurately phase-shaped by user defined phase functions. From our experiment we measure the group velocity dispersion of air at 800 nm to be 20.1+/-1.5 fs(2)/m, which is in good agreement with published values. We consider this method for remote characterization and dispersion compensation to be an important step towards the development of reliable applications requiring the propagation of ultrashort pulses to remote targets.

The paper reports on recent progress towards systematic chemical recognition using shaped femtosecond laser pulses. The ability to generate highly accurate phase functions in which retardation is limited to two values, 0 and π, allows one to carry out an exhaustive evaluation of a 10-bit binary function set in minutes. Upon mining the resulting mass spectra, shaped pulses are found that can be used to uniquely identify a molecule (including structural isomers and stereoisomers) by the resulting fragmentation and ionization pattern. This approach is described and its successful application demonstrated.

The accuracy and precision metrics required by analytical chemistry are met with a method based on phase shaping and coherent control of photofragmentation and ionization. Real-time identification of chemical agents and mixtures will be demonstrated.

Biophotonic Solutions, Inc. Okemos, MI48864, Pastirk@biophotonicsolutions.com Abstract: Coherent control ofphotofragmentation andionization process ofanumber oforganic molecules following theexcitation bybinary phase shaped ultrashort laser pulses ispresented. Results provide ahighly reproducible tool forfollowing different fragmentation pathways. ©2005Optical Society ofAmerica OCIScodes: (320.5540) Pulse shaping, (320.7100) Ultrafast measurements Massspectrometry represents oneofthemosttrusted andwidespread meansofthechemical identification. Itisalso apowerful tool inthestudy ofmolecular reaction dynamics inmolecular beams. Control ofcrossed beamreactions isgenerally donebystatistical means(temperature, angle ofcollision) ofthereagents. Themethod presented here replaces oneofthemolecular beamsbyashaped laser pulse whichtakes advantage ofmultiphoton intrapulse interference (MII) tocontrol theexcitation andtheensuing photofragmentation

Coherent control of photofragmentation and ionization process of a number of organic molecules following the excitation by binary phase shaped ultrashort laser pulses is presented. Results provide a highly reproducible tool for following different fragmentation pathways.

Multidimensional chemical detection and identification based on phase shaped femtosecond laser pulses coupled to mass spectrometry is demonstrated. The method based on binary phase shaping (BPS) takes into account the accuracy and precision standards required by analytical chemistry. It couples multiphoton intrapulse interference of ultrashort laser pulses with time-of-flight mass spectrometry (TOF-MS). We demonstrate that BPS-MS provides a rigorous multidimensional technique for the detection and identification of analogues to chemical agents and mixtures in real time. Experimental results on dimethyl phosphite and pyridine illustrate the new approach toward the real-time accurate detection and identification of chemical compounds including isomers.