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چکیده
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Introduction: Laser anti-reflection coatings (LAR) are designed for the most effective anti-reflection results at a specifically defined wavelength. As such, they are ideal for applications involving lasers or other monochromatic light sources. Composite MgF2 (low refractive index) and TiO2 (high refractive index) films are fabricated by reactive ion-assisted coevaporation deposed on BK-7 glass substrate. Aim: The purpose of the present paper is to produce a high reflection mirror for Ar+ laser, multilayers of MgF2 (low refractive index) and TiO2 (high refractive index) have been deposed on BK-7 glass substrate. Material and method: A vacuum system capable of reaching pressures with of 10-7 mbarn (Balzers) and an optical thickness monitor (GSM-420 Balzers), as well as vibrating quartz crystal thickness monitor were mounted in this vacuum system to be able to check the obtained results. Substrate was circular glass with 20mm diameter and 1 mm thickness (BK-7 glass). Pure research grade MgF2 and TiO2 was used and both evaporated the from tantalium crucible separately, at pressures about 2-3×10-5 mbar. MgF2 was coated with 1 nm/s deposition rate and for deposition of TiO2 partial pressure of 5×10-5 mbar was used and coating rate was 0.5 nm/s. Results: Substrate temperature play an important role on refraction index and packing density of thin films has affect on R value. After annealing although reflection power increased by 5%. Increasing of R forl=500nm, by 5% but at other wavelength l<400nm and l>600nm (outside the spectral band width), also reflectivity rises 20 to 30 percent as well. Conclusion: After eleven thin film layers of l/4 (G/ (HL)5/TiO2/Air), mirror with 95% power of reflection over spectral band width of 160nm and nearly 5% of transmission was produced. These parameters are good enough for making front mirror of Ar+laser.
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