Development of a new type of ultrashort and ultraintensive laser using Raman Back Scattering in plasma for laboratories at universities -
In the last 6 years, our group has made large effort to amplify and compress of ultrashort laser pulses by Raman Back Scattering (RBS) in plasma. The goal of this effort is to develop a new type of fsec-type laser of “university size” (compact, not too expensive) with pulses in the range of 50 fsec at ultra-high intensities of 1021 W/cm2 (at such intensities electric field is almost 100x stronger than Coulomb field in Hydrogen atom).
Presently, very large gratings, and therefore prohibitively expensive, are being used in the ultra-high intensity femtosecond lasers. For Raman pulse amplification and compression in plasma, such large size gratings are not needed. Since plasmas have no damage threshold, extremely high power pulses are feasible. The idea of RBS is based on a 3-wave interaction. Namely, if the frequency of the pump pulse, wpp, is larger than that of the “seed” pulse, ws, by the frequency of waves generated in the plasma, wp (wpp – ws = wp), then Raman amplification of the ultrashort “seed” pulse may take place.
The initial experiments at Princeton have provided proof-of-principle of the idea and last year the very exciting results were obtained by demonstration energy amplification ~ 200, intensity amplification ~ 1000 and reaching very important nonlinear regime, in which pulse compression from about 0.6 psec down to 150 fsec was measured (Phys. Rev. Lett., 2005).
Demonstrated, recently, very high amplification and very good compression of laser pulses by implementing a new idea of using 2-passes of laser pulses in plasma, which will be further modified for multi-pulses amplification and compression. This way the system’s efficiency will be significantly increased, and an operating practical system is in the not too far future.
This work is of high interest for application in several scientific and engineering fields, hence of government agencies like DOE, NSF and DARPA (in August and September last year DOE and NSF funds toward development of a practical device was obtained).
Further development of X-Ray Laser with goal to generate lasing action in “water window” at 3.4 nm for application for X-ray microscopy of biological cells and nanoscale devices –
Intensive works, both theoretical and experimental, were conducted on the ways to improve performance of soft X-ray laser (SXL) at 13.5 nm (important for next generation of lithography) and to develop laser at much shorter wavelength of 3.4 nm in so called “water window”. We have discovered, by numerical calculations, that non-Maxwellian electron energy distribution well explains our measurement of very high gain and lasing action in transition to ground state of H-like Li III ions at 13.5 nm. Further numerical modeling of lasing actions to ground state in H-like ions, particularly for CVI ions at 3.4 nm, reveals that adding H atoms to lasing medium dramatically improves lasing conditions, making very realistic conditions for development ov a compact X-ray laser (university – type system). These calculations were part of Y. Avitzour’s Ph.D. Dissertation ( Princeton Univ. , Jan. 2006) and were also presented in publications.
To test numerical calculations, and particularly effect of adding H-atoms to plasma for improvement its fast cooling, a new experimental system was built for investigation of lasing in H-like He II ions. Unfortunately, good results were not achieved hence additional plasma cooling with H-atoms could not be proved of disproved. One of the reasons for the poor results was too small of a difference in Z of coolant and lasing element. Therefore, during the fall the experiment setup was modified to sue gas jet plasma with higher Z [primarily for Z = 6 (C) and Z = 7 (N)]. The experiments were conducted in collaboration with Prof. Fiedorowich and Dr. Bartnik (form Polish Academy of Science). If the theoretical predictions are confirmed, we will further modify our experimental setup in order to get maximum fsec laser intensity on target (close to 1019 W/cm2) for demonstration lasing action at 3.4 nm in transition to ground state of H-like CVI ions.
A New Approach to Eye Surgery using Femtosecond Laser –
Four years ago a multidisciplinary program on eye surgery using femtosecond laser was established. This program provides a platform for unique collaboration between groups representing ophthalmology (Peter Hersh, MD, corneal and refractive surgery, Opthalmology – UMDNJ), femtosecond alser applications (Szymon Suckewer, MAE – Princeton), polymer science (Richard Register, Chemical Engr. – Princteon), fluid mechanics (Alexander Smits, MAE – Princeton ), lens physiology (Peter Frederekse Physiology – UMDNJ).
Several crucial experiments with very positive results have been achieved. These experiments provide good prognosis for replacement to the well known LASIK method for vision correction by a more precise and less complicated method which we are currently developing. Two Patent Disclosures and two Patent Applications have been submitted. With help from Princeton University ’s Office of Technology Licensing we are in the process of establishing a company, Laser Light Vision (LLV), and discussions with investors about capital funds for technology development and implementation are being conducted.