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High-Power Subpicosecond Laser Applications

#1242


Applications of High-Power Subpicosecond Lasers For Basic Scientific Investigations, Technology, and Biomedicine

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics

Status
3 Approved without Funding

Registration date
12.04.1998

Leading Institute
Vavilov State Optical Institute (GOI) / Research Institute for Laser Physics, Russia, St Petersburg

Supporting institutes

  • Vavilov State Optical Institute (GOI) / Research Institute for Complex Testing of Optical Devices, Russia, Leningrad reg., Sosnovy Bor\nVNIITF, Russia, Chelyabinsk reg., Snezhinsk

Collaborators

  • Lawrence Livermore National Laboratory / University of California, USA, CA, Livermore\nHRL Laboratories, USA, CA, Malibu\nOsaka University / Institute of Laser Engineering, Japan, Osaka\nMax-Planck-Institut fur Quantenoptik, Germany, Garching

Project summary

The Project purpose is performing of basic scientific investigations and obtaining of practical results in technology, measurement technique and medicine using high power subpicosecond lasers. To attain these ends we are going as to create new laser systems and use laser systems created in the frame of Project ISTC #107.

Previous project #107 resulted in development of technologies for production of key optical elements for lasers that use the technique of chirped pulses amplification (CPA) with their subsequent compression. They include methods for obtaining single picosecond pulses with contrast up to 107, methods for spectrum broadening and compression of picosecond pulses of high power, technology for production of high-efficiency diffraction gratings with the aperture up to 20 ґ 40 cm2, diffraction efficiency over 90% and damage threshold above 250 mJ/cm2 for pulses with duration 1 ps, technology for obtaining focusing mirrors with diameters up to 20 cm and focusing spot 10 mm. All this permitted to create in the participant institutes laser systems on neodymium glass with peak power from 1 to 30 TW, pulse duration 0.3 - 1.5 ps that permit to obtain intensities up to 1019 W/cm2. Such superstrong light fields were used for investigation of their interaction with the matter, in particular, absorption and scattering of waves with different polarization states, and generation of X-radiation. Besides that, during the works on the Project, we found out the possibility of application of the technique of generation and amplification of chirped pulses for precision measurement of distances and velocities of objects, which, in principle, can be used for creation of precision laser ringefinders and lidars.

The tasks of the Project:

The works on the project will result in:


- application of the picosecond laser system with the power level in a channel 30 TW for investigation of spectra of hard X-radiation and fast particle at the intensity of laser radiation on the target up to 1019 W/cm2;
- investigations of methods for formation of spatial and temporal structure of subpicosecond laser pulses;
- investigations of applications of pico- and subpicosecond laser pulses in range measurements, technology and medicine. Use of subpicosecon laser pulses in range measurement allows essentially to improve the accuracy of measurements, and their use in technology and medicine enables to make considerably more precision processing of materials and biotissue, than in case of long laser pulses.
- research and development of compact high-peak and average power pico- and subpicosecond solid-state lasers applications in technology, medicine, and range measurements;

The Project will provide opportunity for specialists from defense spheres to take part in basic and applied research in peaceful purposes, in international integration of scientists, and will promote the scientific potential of Russia.

Supposed results:


- Acquisition of experimental and theoretical results of investigations of power and spectral parameters of hard X-radiation with quanta energies up to 1 MeV.
- Acquisition of data for ultrashort and high intense laser plasma interaction: high energy particle transport and energy deposition efficiency under various plasma conditions; channel formation physics under various plasma conditions.
- Application of the technique for generation and amplification of chirped pulses for precision measurement of distances and velocities.
- Research and development of methods for formation of spatio-temporal structure of subpicosecond pulses including additional pulse compression, phase conjugation etc.
- Research and development of models and applications of subpicosecond laser pulses for biomedicine and technological purposes.

Elaborated during the Project fulfillment technologies of the fabrication of the new optical materials (glasses, crystals, coatings), new optical components (diffraction gratings, amplifiers, laser radiators, electrooptical devices etc.) as well as methods of intense subpicosecond pulse generation, methods and software for numerical calculations, the means of the laser radiation and plasma diagnostics may be widely used in the various related fields of science and engineering.

Technical approach and methodology

For investigation of generation of hard X-radiation and superthermal particles, the approach will be used based on exposure of solid-state targets of different structure and composition by focused (to provide intensities 1016 - 1019 W/cm2) 30-TW pico- and subpicosecond laser pulses and measurement of spectral and energy parameters of superthermal particles and hard quanta and subsequent optimization of their yield by variation of spatio-temporal parameters of heating radiation.

To solve the Project tasks in this direction, the existing research developments will be used, which were performed earlier, and within the frames of the ISTC Project No 107:


- 30-TW laser on neodymium glass with pulse duration 1 - 1.5 ps and subpicosecond multiterawatt laser on neodymium glass with pulse duration < 1 ps (Sosnovy Bor, St.Petersburg);
- the set of diagnostics of laser radiation, including autocorrelators, oscilloscopes, energy meters, CCD chambers, spectrographs and other devices.
- target chamber with mirror focusing objective that provides focusing of 60 % of radiation energy in a circle 10 mm in diameter and the intensity on a target up to 1019 W/cm2 (Sosnovy Bor);
- plasma calorimetry, including calorimetric measurements of scattered laser energy and direct measurements of plasma energy (Sosnovy Bor);
- ion-collector measurements of free path time in plasma ion current (Sosnovy Bor);
- spectrometry of X-radiation in the energy range 1.5 - 9 keV on the basis of semiconductor detectors (Snezhinsk), spectrometry of hard X-radiation (up to 56 keV) on the basis of narrow-band filters with photomultipliers and scintillation technique (Snezhinsk), obtaining integral X-ray images by means of multi-channel cameras-obscures in the range of quanta energies < 5 keV with spatial resolution 5 - 10 mm (Snezhinsk).

To fulfill the Project tasks on improvement of methods for determination of parameters of laser radiation on the target surface in each experiment, it is proposed to modernize the existing techniques:


- of energy spatial distribution (on the basis of application of CCD-arrays located in the focal plane of a lens equivalent to focusing one (Sosnovy Bor, St.Petersburg);
- methods for measuring the profile and controlling the power contrast of picosecond pulses by means of electrooptical devices with the use of automated correlation devices (Sosnovy Bor, St.Petersburg);

To fulfill the Project tasks on creation and modernization of means of X-ray and corpuscular diagnostics, the following works will be performed:


- modernization of spectrometer for hard X-radiation on narrow-band filters with photomultipliers and scintillation technique to provide measurements of spectra up to 80-100 keV (Snezhinsk),
- creation of a spectrometer of hard X-radiation for measurements of X-ray quanta from 100 keV to unities of MeV (Snezhinsk),
- creation of diagnostics means for measurement of spectra of particles (ions and electrons) with energies up to unities of MeV (Sosnovy Bor, Snezhinsk).

Production of laser targets will be performed at the RFNC-SRILTP (Snezhinsk) on the basis of existing technology and equipment that was used earlier, in particular, in the program on laser fusion. The technologies permit to produce different targets, including creation of multi-layered targets with thickness of layers 0.1 - 1 mm with the error of 0.03 mm.

The following computer programs existing at RFNC-SRILTP and SRILP will be used for planning experiments on interaction of a picosecond laser with targets, and for processing and analysis of experimental results:


- For modeling of gas dynamic motion and thermodynamic parameters of plasma under conditions of high power laser irradiation including main physical processes (programs "Era", "Tiger-3T", codes "Osvetka" and "Sphera")
- For calculation of fast electrons and X-ray transfer in various approximations {"Era", "Prizma");
- For calculation of fast electrons and X-ray transfer by Monte-Carlo method using 3D program "Prizma";
- For calculation of electromagnetic fields and relativictic electron motion by particles method using 2D program "PM2D".

The performed experiments and computer simulations will be the basis for proposal of an improved model for transformation of energy of high-power laser radiation in the energy of hard X-radiation and superthermal particles in laser plasma of solid targets.

The existing Terawatt picosecond facility (St.Petersburg) will be used for investigation of methods for formation of spatio-temporal structure of high-power subpicosecond laser pulses. It will be used for investigation of possibility of application of wavefront phase conjugation for correction of phase aberrations in laser systems with amplification of chirped pulses. This facility will be also used for study of temporal profiling of subpicosecond pulses by controlling spectral-phase composition of radiation in stretcher and/or in regenerative amplifier and additional spectrum broadening as a result of phase self-modulation. Calculations and preliminary experiments show that both subpicosecond pulses with high contrast and generation of specially profiled (in time) pulses is possible in such a way.

To simulate these phenomena, which arise at propagation of laser radiation in laser systems with nonlinear elements, the following computer codes will be used that exist at SRILP:


- for simulation of amplification of broad-band chirped pulses with consideration for the actual luminescence contour of the active medium,
- for simulation of phenomena of phase self-modulation that cause broadening of spectrum of the amplified pulse,
- for simulation of phenomena of large-scale self-focusing and small-scale filamentation that cause limitation of the peak power of laser radiation,
- for simulation of SBS phenomena that are used for wavefront phase conjugation and compression of pulses.

The technique of amplification of several chirped pulses overlapped in time will be used with subsequent registration of their spectra by a spectrograph and CCD-camera to use supershort pulses in problems of remote probing. The spectrum of these pulses contains information about time delay between the pulses and their phase, consequently, about the distance to the object and its velocity. To perform preliminary experiments, the starting complex on phosphate neodymium glass will be used, which is a part of the Terawatt facility and consisting of the master oscillator, stretcher and regenerative amplifier. The duration of the initial pulse in this system is 1 ps, which determines the accuracy of distance measurements - about 0.3 mm. To increase the accuracy by approximately 10 times, it is proposed to create a compact subpicosecond laser on NdrGlass and (or) Yb:YAG which will be also used for investigation in the filds of technology and biomedicine.

Repetition-rate lasers on Nd:glass and (or) Yb:YAG will be used with supershort duration, and corresponding diagnostic methods to investigate the schemes application of supershort pulses in biomedicine(dental research, surgery) and technology(drilling, cutting etc).


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