Free Spectral Range of Etalon Calculator

Free Spectral Range Formula:

\[ FSR = \frac{\lambda^2}{2 \cdot \eta_{core} \cdot x} \]

Free Spectral Range Wavelength:

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1. What is Free Spectral Range of Etalon?

Free Spectral Range (FSR) is the distance between adjacent peaks in the optical wave of an etalon. It represents the wavelength spacing between successive interference maxima or minima in an optical resonator or interferometer.

2. How Does the Calculator Work?

The calculator uses the Free Spectral Range formula:

\[ FSR = \frac{\lambda^2}{2 \cdot \eta_{core} \cdot x} \]

Where:

\( FSR \) — Free Spectral Range Wavelength (m)
\( \lambda \) — Wavelength of Light (m)
\( \eta_{core} \) — Refractive Index of Core
\( x \) — Slab Thickness (m)

Explanation: The formula calculates the spectral spacing between adjacent resonance peaks based on the wavelength of light, refractive index of the core material, and the physical thickness of the slab.

3. Importance of FSR Calculation

Details: Accurate FSR calculation is crucial for designing optical filters, wavelength division multiplexing systems, laser cavities, and spectroscopic instruments where precise wavelength separation is required.

4. Using the Calculator

Tips: Enter wavelength in meters, refractive index (dimensionless), and slab thickness in meters. All values must be positive and non-zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is an etalon in optics?
A: An etalon is an optical interferometer that consists of two parallel reflecting surfaces. It creates interference patterns used for wavelength selection and filtering.

Q2: How does FSR relate to optical resolution?
A: FSR determines the maximum wavelength range without overlap between adjacent orders. Higher FSR allows for broader wavelength coverage but may reduce resolution.

Q3: What factors affect the Free Spectral Range?
A: FSR is inversely proportional to the refractive index and slab thickness, and proportional to the square of the wavelength.

Q4: Can this formula be used for fiber optics?
A: Yes, this formula is applicable to planar waveguides and fiber-based etalons where the core refractive index and physical dimensions determine the spectral characteristics.

Q5: What are typical FSR values in practical applications?
A: FSR values typically range from picometers to nanometers depending on the application, with smaller FSR values providing finer spectral resolution.