Air-spaced Etalons - Advantages

• Shorter lead times – hundreds of spacer and plate stock options available ready for assembly
• Superior thermal stability
• Mechanically more robust if free spectral range is large
• Mirrors can be coated simultaneously, resulting in near perfect matching
• Potentially better effective finesse
• Can be pressure or tilt tuned

Air-spaced Etalons - Limitations

• Physically larger
• Less rugged

Solid Etalons - Advantages

• More compact
• Can be temperature tuned
• More rugged, unless free spectral range value is very high

Solid Etalons - Limitations

• Poorer thermal stability
• Practical limit to the thickness
• Potential for mismatch of reflector coatings
• Higher defects potential
• Materials limitations