Abstract
A refractive index (RI) tunable polysiloxane coating was fabricated based on the cross-linked network structure embedded with mesoporous silica nanoparticles (MSNs), in which the MSNs were utilized to modulate the RI as well as to support the interior structure of the polysiloxane coating. The Si–O–Si inorganic backbone structure in combination with characteristics from the photopolymerization of active bonds produced the main cross-linked network structure, and controllable embedding of MSNs constructed the network-sphere structure. This approach eliminated the high-temperature post-treatment that was needed to remove the template, which ensures the safe application for temperature-sensitive laser crystal substrates and avoids coating structure collapse. In addition, degradation of the resulting coating can be minimized due to the similar chemical formation between MSN and polysiloxane coating. Hereby, a polysiloxane coating with expected spectral and laser damage-resistant properties can be obtained. This will facilitate the fabrication and application of a laser component with both high-transmission and high-flux capability for a high-power laser system.
Highlights
Silica-based coatings are widely applied in the fields of photovoltaics [1,2], LEDs [3], lasers [4,5], energy and fuel [6,7], catalysts [8], and corrosion protection [9], owing to its excellent optical and mechanical properties
The refractive index (RI) of the polysiloxane coating can be continuously modulated in a wide range, and the coating structure can be well protected for further application in high-power laser systems
The polysiloxane sol and colloidal mesoporous silica nanoparticles (MSNs) sol were mixed in mass proportions of 1:0, 1:4, 1:7, 1:16, and 1:25 to construct the network-sphere structure, in order to tune the coating RI according to different proportions
Summary
Silica-based coatings are widely applied in the fields of photovoltaics [1,2], LEDs [3], lasers [4,5], energy and fuel [6,7], catalysts [8], and corrosion protection [9], owing to its excellent optical and mechanical properties. Polysiloxane coatings are one of the silica-based coatings that have been applied in high-power laser systems as the moisture-resistant layer to protect the water-soluble laser crystal KH2PO4 (KDP) and KD2PO4 (DKDP) from water invasion [13]. This type of coating is conventionally fabricated through the hydrolysis and polycondensation of siloxane using the sol-gel technique [14,15,16]. The MSN is organic–inorganic with a main Si–O–Si structure and plenty of hydroxyls over its surface, which could help MSNs to incorporate well with the polysiloxane oligomer Based on this design, the RI of the polysiloxane coating can be continuously modulated in a wide range, and the coating structure can be well protected for further application in high-power laser systems
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