Development of Composite Polymer-Glass Edge Claddings for Nova Laser Disks

Abstract

Large Nd:glass laser disks for disk amplifiers require an edge cladding which absorbs at 1 μm. This cladding prevents edge reflections from causing parasitic oscillations that would otherwise deplete the gain. We have developed a composite polymer-glass edge cladding that consists of absorbing glass strips bonded to the edges of laser glass disks using an epoxy adhesive. The edge cladding must survive a fluence of approximately 20 J/cm2 in a 0.5-ms pulse. Failure can occur either by decomposition of the polymer or by mechanical failure from thermal stresses which leads to bond delamination. An epoxy has been developed that gives the required damage resistance, refractive index match and processing characteristics, A slight tilt of the disk edges greatly reduces the threat from parasitic oscillations and a glass surface treatment is used to promote bond adhesion. Laser disks fabricated with this new cladding show identical gain performance to disks using conventional fused-glass cladding and have been tested for over 2000 shots (equivalent to about a 4-year lifetime on Nova) without degradation.

High‐Power Solid‐State Lasers: a Laser Glass Perspective

“…The cladding is bonded to the edges of the laser glass disks or slabs and absorbs the ASE, thereby preventing parasitic oscillations from developing. Adhesively bonded edge claddings have been developed and are now widely used in the United States, Europe, and Japan 38,84 . Two‐part optical epoxies and polyurethanes are currently the most widely used adhesives.…”

“…Adhesively bonded edge claddings have been de-veloped and are now widely used in the United States, Europe, and Japan. 38,84 Two-part optical epoxies and polyurethanes are currently the most widely used adhesives. In general, epoxies are used for HEHP applications 84 whereas polyurethanes are more commonly used for HAP lasers.…”

“…38,84 Two-part optical epoxies and polyurethanes are currently the most widely used adhesives. In general, epoxies are used for HEHP applications 84 whereas polyurethanes are more commonly used for HAP lasers. 38 Polyurethanes have good moisture resistance and are the best choice for the HAP watercooled slabs.…”

“…Polyurethanes have good moisture resistance and are the best choice for the HAP water‐cooled slabs. In contrast, the refractive index of optical epoxies can be very precisely modified to match the glass refractive index 84 and are a better choice for HEHP laser slabs with multikilojoules of stored energy.…”