With the development of space lasers, research on the stability of laser films in space environments is becoming more and more important. The space laser film will be damaged by protons, gamma rays and other space radiation environments, and it will be affected by laser radiation, too. This puts forward higher requirements for space laser film elements, so it is essential to carry out space environment simulation tests on laser films. In this paper, the effect of 40keV proton on SiO2 film was studied and then the 355nm laser damage threshold test on it was performed. It was found that the ultraviolet absorption of the film irradiated by proton increased, resulting in the decrease of its transmittance and its ability to resist laser damage.
Low dispersive with broad bandwidth mirrors serve as indispensable elements in ultrafast laser systems. We report on three coatings, quarter-wave high reflection mirror, metal-dielectric mirror and ternary composite mirror, which are suitable for broad bandwidth high reflection (BBHR) with 800nm center wavelength. Mirrors based on quarterwave Ta2O5/SiO2 layers are designed and fabricated. By depositing the quarter-wave HfO2/SiO2 layers on the metallic material, we have achieved the mirror with lager low-dispersive bandwidth, this design takes advantage of broad high reflection bandwidth of metal and high laser induced damage threshold (LIDT) of HfO2. Moreover, we have deposited HfO2/SiO2 layers on Ta2O5/SiO2 layers, since HfO2 demonstrates higher damage threshold than Ta2O5, such combination reach an ideal trade-off between the low-dispersive bandwidth and high LIDT comparing with traditional quarter-wave Ta2O5/SiO2 layers. Our BBHR mirrors are produced by means of dual-ion-beam sputtering technique. The designs afford low group delay dispersion (GDD) for reflected light over the broad bandwidth in order to minimize temporal broadening of the fs pulses. The design’s GDD behaves in a smooth way, and its electric field intensities show promise for high LIDTs. Reflectivity and GDD measurements indicate good performance of the BBHR design. LIDTs of the produced BBHR mirrors are also tested and compared.
Multiple-pulse laser-induced damage is an important topic for many applications of optical coatings. In this work, we study the performance of multiple and single pulse laser-induced damage of anti-reflection (AR) coatings with ns-pulsed laser irradiation at a wavelength of 355 nm. LIDT of AR coatings changes little under multiple and single pulse irradiation, around 15 J/cm2. The damage probability curve of multiple pulse is extremely steep. The defect density in the irradiated area is quite high, a large amount of pin-point or cone-shaped pits are observed. The absorption coefficient and defect density increase a lot under multiple pulse irradiation. Material modification of the precursor under multiple pulse is thought as the main reason of high absorption coefficient. Once damage occurs, the damage increases fast and soon grows catastrophic damage. The initial damage morphologies are similar, pin-point or cone-shaped pits, which indicates the initial precursor or defect of multiple and single pulse are the same.
Space laser systems are widely used in communication, altimeter and Doppler radar. UV laser, which possesses high spectral resolution and provides with the detection of the parallel polarized molecular (Rayleigh) and particle (Mie) backscattered signals has promising use in atmosphere detection and Doppler radar. No orbiting satellite carrying with 355nm laser has yet been launched owing to the laser induced damage of coatings. Coatings for spaceborne laser system are widely used in spacecraft with laser system to improve the transmittance of the optical system and to adjust the laser beams. An effective way to improve the lifetime of the coatings and the resistance to the environment is to increase laser induced damage threshold (LIDT). The subsurface damage (SSD) of the substrate is one of the major harmful factors in laser induced damage. In our study, 355nm high-reflection (HR) and anti-reflective (AR) coatings deposited by dual-ion beam sputtering (DIBS) were stable and showed lit
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