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Types of Etalon

The optical etalon can be a single-piece structure with parallel reflective surfaces, the solid-state etalon made of fused silica material, or an air-gap structure using a Fabry-Perot cavity double-reflective mirror, i.e., the air-gap etalon. 

1. Solid Etalon:

Photonchina Specifications:

Material: H-K9L/BK7, Quartz Glass

Flatness：λ/60、λ/80、λ/100;

Finesse：F≥25、F≥35、F≥45;

Diameter (mm): Size: 1×1mm~25.4×25.4mm；φ3~φ25.4mm；

Thickness(mm):0.5, 1, 2, 3, 5, 10, 20, 30, 40, 50 etc.

FSR(GHz):1, 1.3, 2.6, 3.4,5, 10, 34, 50, 103, 184 etc.

Note: Customized products are available upon request.

2. Air Gap Etalon：

Photonchina Specifications:

Material: H-K9L/BK7, Quartz Glass

Flatness：λ/60、λ/80、λ/100;

Finesse：F≥25、F≥35、F≥45;

Size: 1×1mm~25.4×25.4mm；φ3~φ25.4mm；

Thickness(mm):0.5, 1, 2, 3, 5, 10, 20, 30, 40, 50 etc.

FSR(GHz):1.5, 3, 3.75, 5, 15, 30, 50, 107, 268 etc.

Note: Customized products are available upon request.

Fabry Parot Etalon is a high-resolution interference spectrometer with wide applications, which include high-resolution spectroscopy, the study of spectral lines with very close wavelengths, such as the isotope spectrum of elements, the hyperfine structure of the spectrum, the small frequency shift in light scattering, the Doppler shift of spectral lines caused by atomic movement, and the internal structure shape of spectral lines. 

It can also serve as a high demanding optical filter and a precision wavelength meter. In the laser system, it is often used to narrow the spectral line in the cavity or make the laser system operate in a single mode. It can be used as a bandwidth control and tuning device in broadband picosecond lasers to detect and analyze the spectral  components in the laser (longitudinal mode, transverse mode).

Use of etalon and selection of substrate materials

Etalons, when used in transmission mode, have a series of transmittance peaks with periodic frequency spacing and are typically used in telecom for wavelength locking. Etalons are characterized by their Free Spectral Range (FSR) – the frequency spacing between peaks – and their Finesse – which essentially governs the shape of the transmission peaks.

Etalon filters typically consist of a single spacer layer with two reflector stacks on either side.

Different substrate materials are chosen depending on the application – fused silica is used when the etalon FSR and peak variation with temperature is to be minimized while Si is used when a high FSR temperature coefficient is required for thermal tuning.

Photonchina fabricates custom high quality fused silica and Si etalons at competitive prices with FSR values in the range of 12.5 GHz to 500 GHz.