Tunable Infrared Laser with Frequency Doubling
CO2 Lasers Tunable Over a Broad IR Spectrum with Effective Frequency Doubling in Nonlinear Crystals
Tech Area / Field
- PHY-OPL/Optics and Lasers/Physics
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- B.I. Stepanov Institute of Physics, Belarus, Minsk
- Max-Planck-Institut fur Quantenoptik, Germany, Garching\nLaser und Medizin-Technologie, Germany, Berlin\nRice University / Electrical and Computer Engineering Department, USA, TX, Houston
Project summaryThe Project primary objective is to create powerful and effective sources of coherent radiation able to cover vast sections in the mid IR spectral range (4.5 ё 17.5 mm). Construction of these devices is topical for handling many challenging tasks. Powerful coherent mid IR radiation provides the possibility of resonant influence upon vibrational transitions practically of all molecules known in nature, which is the basic principle of multiphoton laser chemistry, laser isotope separation and purification of substances, remote and local gasometry, etc.
CO2 lasers are the most extensively used in the mid IR range. They surpass all other known mid IR sources in the combination of the basic output characteristics: power, monochromaticity, pergence, stability. Moreover, they have large efficiency, are distinguished in design simplicity and high reliability, and suitable in use. However, generation spectrum of ordinary used CO2 lasers is limited to a number of inpidual vibrational-rotational lines (about 100) in the narrow spectral range 9.2 - 10.9 mm, which essentially narrows the solvable problem area associated with resonant influence upon substances. The most simple and natural way to overcome this difficulty is to expand spectral capabilities of well showing CO2 lasers at the expense of nontraditional and new laser transitions as well as of effective frequency doubling in nonlinear optical crystals. This way demands much less efforts and means than development and fabrication of more complicated laser systems, for instant, those based on optical parametric oscillators (OPO) or exploration for new active media.
The proposed Project is oriented toward development, creation, and optimization of rather powerful and comparatively effective CO2 laser sources capable to tune over a great amount of lines (about 1000) by means of the above scientific approach. In so doing the most completely settled spectral ranges are the 4.5 - 6.0 mm and 8.5 - 12 mm, where the atmospheric windows exist, as well as the 13.5 - 17.5 mm range, essential in many applications (for example, in laser isotope separation).
The 8.5 - 12 mm and 13.5 - 17.5 mm considerable extension of the CO2 laser spectral output will be achieved due to exploitation of the frequencies produced in the nontraditional 0002 - 1001 (0201), 0003 - 1002 (0202) [1-5]; 0l1l – ll10 (0310) [6-8]; 0201 (1001) - 0111  and new 0221 - 1220, 1001 - 2000, 0201 - 1200, 0112 -1111 [10-12] transitions in addition to the ordinary used ones 0001 - 1001 (0200). We have already got a generation at a number of nontraditional and new transitions [2-12] (at some of them comparable in efficiency with traditional case). Essential extra broadening of spectrum is then expected at the indicated transitions as a result of utilization of carbon dioxide isotopic molecules such as 13C16O2 and 12C18O2.
The 4.5 - 6 mm range should be covered by means of effective frequency doubling of CO2 laser radiation in nonlinear crystals. This scientific approach is widely used in the visible range for broadening generation spectrum of approved lasers. As for the mid IR range, the efficiency problem of nonlinear conversion has not yet been solved, which restricts its application for handling many practical tasks. The point is that growing crystals competitive to the best visible samples in optical and nonlinear properties is a very complex technological process. As a part of this Project we intend to carry out a series of researches aimed at realization of new technologies for growing highly efficient IR crystals. Besides, it will be possible to compensate partially for insufficient conversion efficiency by using originally designed optical systems of a high efficiency. Exploration and development of extraordinary systems for nonlinear conversion and of optimal operational regimes of laser sources are still essential in the mid IR range.
By now, we have already started our investigations in this direction. The technology has been developed for and the first experimental samples have been produced of the ZnGeP2 and AgGaSe2 crystals [13,14] not yielding optical and nonlinear properties to the best worldwide samples, including Cleveland Crystals Inc. (USA). The extraordinary technique has been proposed and corroborated experimentally for frequency doubling in IR nonlinear crystals mounted instead of a CO2 laser output mirror . Investigations connected with the development of original nonlinear conversion systems are to be continued as a part of the present Project. As well, we intend to develop the technology and to grow rather more effective nonlinear crystals on the basis of doping additives.
Within the frameworks of this Project we suggest to develop, fabricate, and optimize throughout two CO2 lasers broadly timed over the IR range, which should be made using the expertise acquired by the RFNC and IP NASB participating personnel as they were involved in research and design of different military laser systems (including super powerful gas lasers):
1. Low pressure CO2 laser excited by longitudinal both continuous and pulse-periodic electric discharge and tunable over a great number of lines (about 1000) in traditional, nontraditional, and new bands with a power of СW generation at the strongest line in each of the above listed bands more than 10 W, 5 W. 0.3 W and about ten times higher pulsed-periodic values.
2. Pulsed TEA CO2 laser tunable over many lines (about 500) in traditional, nontraditional, and new bands with the 5 J, 2 J, and 0.3 J generation energy corresponding to the 20 MW, 5 MW, and 1 MW peak power at the strongest line in each of the bands.
These lasers have the unique spectral advantages compared with all previously developed CO2 lasers.
1. Development of a combined (temperature&level) theoretical model describing operation of longitudinal-excited low pressure and TEA CO2 lasers.
2. Creation of a software for numerical modeling of kinetic processes occurred in active media and calculations of output parameters of CO2 lasers on the basis of the combined model.
3. Calculations of extreme energy and spectral characteristics; optimization of active media, pumping, and cavities of CO2 lasers, both longitudinal-excited low pressure and TEA, broadly tuned over many lines in traditional, nontraditional, and new bands (including the case of 13C16O2 and 12C18O2 molecules).
4. Creation and optimization of a laboratory low pressure CO2 laser excited with longitudinal both continuous and pulsed-periodic electric discharge and tunable over many (about 1000) lines in traditional, nontraditional, and new bands with a power of CW generation at the strongest line in each of the above listed bands more than 10 W, 5 W, 0.3 W and about ten times higher pulsed-periodic values.
5. Development, creation, and optimization of a laboratory pulsed TEA CO2 laser tunable over many lines (about 500) in traditional, nontraditional, and new bands with the 5 J, 2 J, and 0.3 J generation energy corresponding to the 20 MW, 5 MW, and 1 MW peak power at the strongest line in each of the bands.
6. Realization of sufficiently powerful and effective generation of the CO2 lasers, both longitudinal-excited low pressure and TEA, at new vibrational-rotational transitions.
7. Realization of sufficiently powerful and effective generation of CO2 lasers, both longitudinal-excited low pressure and TEA, at a great amount of new vibrational-rotational transitions in isotopic molecules 13C16O2 and 12C18O2.
8. Growing of effective nonlinear crystals AgGaSe2 not yielding optical and nonlinear properties to the best worldwide samples.
9. Development of a technology for and growing of new highly efficient nonlinear IR crystals.
10. Development and experimental embodiment of new effective frequency doubling systems for the CO2 lasers.
As a result of accomplishing the program works based on many years' experience and experimental basis accumulated in developing and fabricating laser systems of a specific appointment, including those carried out against orders of the defense establishments, novel IR laser sources should be created having no analogous all over the world. Analysis indicates that they could be competitive for completing LIDAR stations and other laser monitoring systems.
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