Tunable Air Spaced Etalons

Fused Silica; Wavelength Range Customer Specified; Finesse Customer Specified; FSR Customer Specified; AR-coated; Dia. 14-203.2 mm; Clear Aperture 4-150 mm

LightMachinery’s series of tunable air spaced etalons is manufactured from Fused Silica using the company’s patented fluid jet polishing (FJP) technology – allowing the adjustment of the etalon’s shape and flatness to within a few nanometers. These tunable air spaced etalons are available as 14 mm diameter, 4 mm aperture, single piezo tube (OP-1986) or larger 3-piezo tunable etalons (OP-740xT) with diameters of 50.8 to 203.2 mm and 30 to 150 mm aperture.

Wavelength range, finesse, free spectral range (FSR) and design details can be realized based on customer requirements. For the OP-1986 single piezo tube tunable etalon, a dedicated driver and mount Kit (OP-7934) is available that includes everything required to drive the single-tube piezo including power supply, driver with computer interface, cables, connectors and a mount that adapts the single tube piezo etalon to a standard 25.4 mm (1") diameter optical mount – made from Delrin and aluminium.

There are a number of ways to tune etalons including tilting the entire etalon, moving the mirrors and changing the index of the medium (pressure, temperature, electrostatic). Tilt tuning is a simple tuning technique. As the etalon is tilted, the FSR changes with the cosine of the angle.

Piezo-electric tuning of an air spaced etalon is usually what is meant by the phrase "tunable etalon". This technique can tune the etalon quickly by changing the size of the air gap. By changing the length of the air gap by half the wavelength of the light, the transmission peak moves one full FSR. So, if an etalon is used at 532 nm then only 266 nm of motion is required to tune the etalon.

Small piezo elements (like the OP-1986 single piezo tube tunable etalon) can easily move through 10 µm. Larger OP-740xT piezo tunable etalons are made using three piezo elements. Although these etalons are more complex to control, they have the big advantage that the piezo elements can be subtly tuned to eliminate any residual tilt error between the two mirrors and improve the finesse.

Etalons are optically transparent, flat components with very precisely parallel reflecting surfaces. While solid etalons consist of solid plates of optical material, air spaced etalons are formed by two mirrors with an air gap between them, reducing the problem of temperature dependence. Due to their construction, air spaced etalons are significantly more complex. The outside surfaces of the end mirrors also need to be wedged and AR-coated to avoid reflections from these surfaces causing additional unwanted etalon effects.

Sometimes you need something special – if you are looking for a customized tunable air spaced etalon that exactly meets your specific requirements, please get in touch with the AMS Technologies etalon experts. Our supplier LightMachinery is extremely experienced with specifying, designing and manufacturing custom etalons using the company’s patented fluid jet polishing (FJP) technology. We are looking forward to discussing your customized etalon solution!

Fluid jet polishing (FJP) systems use a fine stream of slurry to accurately remove nanometers of material from an optical surface. Many years of refining this computer controlled polishing technology have enabled LightMachinery to use FJP for the adjustment of the shape and flatness of optical components such as etalon mirrors to within a few nanometers as well as the production of very thin components such as wafers and thin etalons that are impossible to accurately polish using conventional technology.

Key Features:

• Piezo Tunable Etalons
• Etalon Material: Fused Silica (Optical)
• Gap: Customer Specified 5 µm to >200 mm
• Gap Adjustment: Tunable From -4 to +12 µm (-30 to 150 V)
• Maximum Tuning Speed: ~1 KHz For Large Moves, ~10 KHz For Small Moves (One FSR)
• Wavelength Range: Customer Specified
• Finesse: Customer Specified
• Free Spectral Range, FSR: Customer Specified
• AR-coated: Less Than 0.5% Reflection
• Diameter: 14 mm (OP-1986), 50.8 to 203.2 mm (2” to 8”, OP-740xT)
• Clear Aperture: 4 mm (OP-1986), 30 to 150 mm (OP-740xT)

Applications: Spectroscopy; Interferometers; Wavelength Measurement; Fine-structural Investigation of Spectral Lines