New concept weapons, diamond wafer as a new optical window material promising!

Higher, faster, stronger is the requirement for a new generation of weapons of war. Since entering the new century, China has continuously strengthened its national defense and military industry, and as a new optical window material, the excellent characteristics of diamond are vividly reflected in the field of new strategic weapons. It is mainly manifested in the following four aspects:

1. Diamond fairing of supersonic new generation interceptor missiles: At present, when developing high-speed interceptor missiles worldwide, fairings have become key components that must be developed simultaneously, due to high-speed combat missiles, the flight speed at medium and low altitudes of 1 to 3 km is 3 to 4 Mach, the surface temperature of the missile reaches 600 ° C, and at a height of 3 to 30 km, the speed is above Mach 6, such a high speed, so that the surface temperature of the missile quickly rises to more than 1500 ° C. The huge thermal shock makes the traditional infrared optical material simply unable to withstand it, and the diamond film is almost the only choice, especially when the supersonic missile flies at high speed, raindrops, sand and dust and other insignificant natural environments at rest have become a weapon that seriously endangers the missile fairing. The high transmittance, high thermal conductivity, excellent mechanical properties, luminescence characteristics and chemical inertia of diamond can be used as the best application material for optical, such as the protective film of various optical lenses; In military use, the use of radar waves in the penetration of diamond film is not easy to distort the characteristics, can be used as a radome; When aircraft and missiles fly at supersonic speed, the conical radar of the head cannot withstand high temperature, it is difficult to withstand the impact of high-speed rain and dust, and the radome is made of diamond film, which not only dissipates heat quickly, wears well, but also solves the problem that the radome can withstand high temperature sudden changes at the same time in high-speed flight.

2. High power laser window: High power CO2 laser is an important part of high energy laser weapons. At present, the bottleneck of CO2 laser to achieve high power output is the "thermal lensing effect" of its output window, and gallium arsenide will cause environmental pollution in the manufacturing process, with a more obvious thermal lensing effect. Because the CO2 laser absorption coefficient of KCL crystals with a wavelength of 10.6 um is very low, and there is no thermal lensing effect, but the mechanical strength of KCL crystals is low, and in the atmospheric environment, it is extremely easy to deliquescence and decompensure, and has not yet obtained industrial applications. Diamond is the best candidate for protection, anti-reflection coating materials, on the other hand, the use of diamond self-support film can replace gallium arsenide (GaAs), zinc selenide as a high-power CO2 laser window, its superiority is mainly in the excellent thermal conductivity of diamond. Although the absorption coefficient of diamond at a wavelength of 10.6um is 2 to 3 orders of magnitude higher than that of zinc, the thermal conductivity is 100 times higher than that of zinc selenide, so when used at high power, its temperature rise is much smaller than that of zinc selenide.

Table 1 Comparison of the characteristics of   diamond and ZnSe

3. High-power microwave window: A key technology in high-power microwave weapons is the refrigeration of microwave windows, high-power operation, the thermal effect of traditional window materials is obvious, and toxic cryogenic measures need to be taken, because the dielectric loss of optical grade diamond film in the microwave band is very low, only 8 to 15 × 10-6 in the range of 72 to 145GHz, so it can be used as a window material for high-power microwave tubes. A typical application that the U.S. military is developing and researching is the window for a cyclotron oscillator that operates at 70 to 170 GHz with an output power of more than 1MW. Recent findings suggest that this application requires an optical grade diamond film with a diameter of 100mm and a thickness of 1.6 to 2.3 mm, which does not exceed 15 °C at a microwave power of 1.2 MW without the need for a cooling system.

4. Photoelectric countermeasure protective materials: In the optoelectronic confrontation, the optical film is the first part of the optical weapon system such as reconnaissance, sighting, and guidance, and it is also a weak link that is easy to damage, and the damage of the laser to the optoelectronic equipment first damages the optical film, and then destroys the optical components and optical systems, and the diamond film has a high threshold of anti-laser damage, coupled with its high transmittance to infrared light, and does not affect the performance of infrared weapons and equipment after coating. This makes diamond an ideal optoelectronic protective material against laser damage.

Figure 2 Comparison of the Knoop hardness of the material and the laser erosion wear rate

CSMH is a focus on the research and production of diamond enterprises, the core products are   diamond wafer, diamond heat sink, diamond-based gallium nitride epitaxial wafer and aluminum nitride film, etc., the product quality has reached the world's leading level. The thermal conductivity of diamond thermal sinks is as high as 1000-2000W/m.k, and the surface roughness of diamond wafer growth surface Ra < 1 nm. At present, the products are widely used in 5G base stations, lasers, new energy vehicles, new energy photovoltaics, aerospace and national defense military and other fields.