Optical Diamond Microturning of Crystals for Lasers pra-0086

Full Title Optical Diamond Microturning of Crystals for Lasers Tech Area / Field

PHY-OPL: Physics / Optics and Lasers

Brief Description of Technology Modern laser projects impose high requirements for the quality of optical treatment of laser system elements. Since the area of optical elements reaches up to 4040 cm, the complexity of the problem is evident.

Most difficult is the optical treatment of optical elements made of water-soluble crystals (KDP, etc.) that serve for pulse duration control and light frequency conversion in laser systems. Experience has shown that these requirements cannot effectively be met by traditional polishing methods using a free abrasive.

Thus, in some scientific centers — in particular, IAP RAS — the optical treatment method is being developed based on a diamond cutting tool, or a single specially cut diamond. This treatment can, in principle, satisfy the highest demands to the treated surface; some properties of the surface (for example, optical damage threshold) are much higher than surfaces treated by traditional methods. However, this technology needs unique equipment and thoroughly elaborated technology. For example, the diamond microturning device belonging to the leader in this field — the Lawrence Livermore National Laboratory (USA) — costs about $10,000,000 and is being developed by a group of skillful experts at LLNL and the company, Cleveland Crystal Ltd.. No such centers are, obviously, available in Russia.

It is clear, however, that a lone very good center cannot satisfy the requirements of optical treatment for the world community, not all members of whom are able to purchase such equipment. Therefore, in order to fulfill Russian projects employing high-power lasers, IAP RAS began developing in the late 1980s a technology that applied more accessible and less expensive equipment produced in the CIS (i.e. diamond micromilling machine).

The entire complex pertaining to this device has now been brought up to the necessary level, and includes: the machine, the compressed air system, the device parameter monitoring system, the technology and equipment for applying fine films on elements, plus methods and devices for treated surface quality control. Experience has been gained in processing elements of the cross-section ~ 2525 cm, with a nonflatness of ~ 0.3-0.4 mcm and rms roughness at 80-90 A. The treated planes are parallel to <10. The optical elements (2121 cm) fabricated in IAP RAS are successfully applied in large laser systems. The device is capable of treating elements of diameters up to 600 mm. Investigations of characteristic microroughness and vibrostability of the device permit us to draw a conclusion of possible improvement (by approximately 2 to 3 times) of the treated crystal roughness.

Legal Aspects Patents were not sought.

Special Facilities in Use and Their Specifications None.

Scientific Papers V.I.Bespalov, V.I.Bredikhin, V.P.Ershov et al., “Effective technology for fabricating KDP, DKDP crystals to be used in high-energy lasers,” Proc.SPIE v.2633, p.732 (1996).

V.I.Bespalov, V.I.Bredikhin, V.P.Ershov, V.V.Zil’berberg, “Perspectives for creation of highly effective technology of fabricating KDP, DKDP crystals for ICF. Solid-State Lasers for Application to Inertial Confinement Fusion (ICF),” Second Annual Inter.Conf. October 1996, Paris, France. Technical Program & Book of Abstracts, p.62. SPIE (to be published).