Assemblies

Joining Technologies

At LAYERTEC, the following joining technologies are available:

• Optical contacting / bonding
• Ultrashort-pulse laser welding
• Adhesive bonding

Depending on the requirements, passive or active positioning and alignment technologies are employed.

In addition, we specifically prepare optical components for customer-side joining steps, for example by applying solderable coatings on side faces. Further information: Solderable Coatings.

Optical Assemblies

The cavity shown in Fig. 2 consists of two highly reflective mirrors made of fused silica or ULE, coated using sputtering techniques. The mirrors are manufactured according to customer specifications with respect to wavelengths, reflection, and transmission. For a comparable resonator optic, reflectivities of 99.999 % at 1540 nm and 99.998 % at 700 nm with a transmission of approximately 5 ppm were measured.

The optical components are connected by a spacer made of ULE, which is also manufactured according to customer-specific geometry and material requirements. At 1540 nm, a finesse of approximately 250,000 to 300,000 is achieved. The mirrors are joined to the cavity by optical contacting and additional ultrashort-pulse laser welding without the use of further joining materials. Laser welding ensures high mechanical stability and long-term stability of the assembly.

Optomechanical Assemblies

Optomechanical assemblies combine optical elements (e.g., mirrors or lenses) with mechanical mounts, reference surfaces, or adjustment structures to form function-ready subassemblies. The objective is a defined and long-term stable optical function within an optomechanical system.

Typical features include:

• Defined opto-mechanical interfaces
• Controlled tolerances between optics and mechanics in the µm range or better
• Consideration of thermal and mechanical loads
• Use as a pre-aligned subassembly in the customer’s system

The assembly shown in Fig. 3 shows a high-accuracy reference mirror mounted to a mechanically stiff bracket on one end, while the other end rests on a flexible bracket to allow thermal expansion. The example shown features a 600 mm long mirror. Such assemblies are used in precision motion systems (e.g., X-Y stages), where positioning accuracies below 100 nm are required.

The mirror serves as a reference surface on the moving stage, where an interferometer measures small changes in position. Applications include measuring and machining systems in electronics production and ultra-precision mechanical engineering.

Key characteristics:

• Low wavefront distortion; flatness < λ/10 even for substrate dimensions above 300 mm
• High precision of mirror surface to mount interface in the single-micron range
• High bond strength, ensuring precise positioning under high acceleration of several g over the entire product lifetime
• Long-term stable dielectric or metallic coatings for all precision measurement applications such as 632.8 nm interferometry

To realize and verify these requirements, LAYERTEC has comprehensive in-house expertise across the entire process chain—from substrate manufacturing and coating to precision assembly and metrology. More information can be found at Optical and optomechanical Assemblies.