Metallic Mirrors
Metallic mirrors are metal-coated optical mirrors that provide broadband reflections and low chromatic dispersion. At Avantier, we produce custom metallic mirrors for LWIR lasers, infrared optics, and other broadband applications.
Applications
Metallic mirrors are important in spectroscopy and infrared optics, with the choice of mirror depending on the spectral range required for the application. For instance, gold coatings offer very high reflectance in the infrared region, particularly for wavelengths above 600 nm. Silver mirrors provide excellent reflectance in the visible spectral range, from around 500 nm into the near-infrared. More economical aluminum mirrors are effective across a broad spectral range, from approximately 300 nm through the infrared. However, aluminum mirrors have a lower damage threshold than silver and gold, making them less ideal for high-power laser applications.
Gold-coated mirrors are highly desirable for CO2 experiments, and silver-coated mirrors are a good choice for use with femtosecond Ti: Sapphire lasers.
Types of Metallic Mirrors
Metallic mirrors can be divided into two types: first surface mirrors and second surface mirrors.
First Surface Mirrors: In a first surface mirror, the side of the mirror facing the incident light is metal-coated. The light does not reach the substrate; it barely penetrates the coating and is reflected. These mirrors often have an additional enhancement coating over the metallic coating for protection and improved optical qualities. For instance, SiO2 (silica) or Si3N4 (silicon nitride) are often used to protect delicate metal surfaces from oxidation and scratching. Examples of coated mirrors include protected aluminum mirrors, protected silver mirrors, enhanced silver mirrors, and protected gold mirrors.
Second Surface Mirrors: In a second surface mirror, the metallic coating is on the side away from incident light. Light travels through the substrate before reaching the metal and being reflected back. The benefit of these mirrors is that the coating is protected by the substrate, and a protective paint can be applied to the outer surface of the coating for extra protection. The downside of this type of mirror is potential for chromatic dispersion in the glass or Fresnel reflections at the first surface, which can cause ghost images.
The substrate in a first surface mirror might be optical glass or a nontransparent material like aluminum. However, the substrate in a second surface mirror should be transparent to light at the target wavelengths.
Factory Standards
Surface Flatness | λ/4 |
Diameter | +0, -0.2mm |
Surface Quality | 40-20 |
Parallelism | 90% diameter |
Bevel | 0.2mmx45° typical |
Laser Damage Threshold | 0.4J/cm2 for 532nm @10ns pulse (measured) |
Durability | to MIl-C-675 |
Reflectance | R>88% (350-2000nm) |
Custom Metallic Mirrors at Avantier
At Avantier, we produce custom metallic mirrors for our customers in research, medicine, industry, and defense. Our skilled design and engineering teams are able to work with you to determine the ideal design for your application, and we have the manufacturing capabilities to produce the exact metallic mirror you need. State-of-the-art metrology equipment enables us to ensure your mirror meets and exceeds all applicable standards.
Don’t settle for in-stock mirrors that only approximately meet your needs. Get a mirror made to order for your application and experience the precision results that come from using optical parts tailored to your exact specifications.
Call us today to place a custom order or to schedule an introductory consultation.
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