Laser Linewidth and Bandwidth Calculator
Calculate laser spectral linewidth, bandwidth conversion, and coherence properties
Calculate Laser Linewidth and Bandwidth
Calculate Linewidth
Find spectral linewidth from laser parameters
Convert Bandwidth
Convert between wavelength and frequency bandwidth
Laser Linewidth Parameters
Fundamental frequency of the laser emission
Q-factor of the cold laser cavity (damping strength)
Power of the laser mode
Corresponding wavelength: 632.80 nm
Laser Linewidth Results
Spectral Linewidth
Coherence Properties
Key Formula: Δν = (π × h × ν × Γ²) / P
Coherence length: Lc = c / Δν (distance over which laser maintains phase coherence)
Laser Quality Analysis
✅ Excellent monochromaticity - very narrow linewidth
🎯 Ultra-high Q-factor - exceptional spectral purity
🌟 Excellent coherence - suitable for interferometry
Example Calculation
He-Ne Laser (632.8nm, 1W)
Frequency: ν = 473.755 THz
Cavity linewidth: Γ = 1 GHz
Power: P = 1 W
Linewidth: Δν = (π × h × 473.755×10¹² × (1×10⁹)²) / 1 = 0.986 Hz
Coherence length: Lc = 3×10⁸ / 0.986 = 304 million meters
Typical Laser Pointer (635nm, 5mW)
• Frequency: 472.114 THz, Cavity: 10 GHz, Power: 5 mW
• Linewidth: ~19.7 kHz (much broader due to lower power)
• Coherence length: ~15 km (still excellent for most applications)
• Q-factor: ~2.4×10¹⁰ (high spectral quality)
Typical Laser Linewidths
Narrower linewidth = better monochromaticity
Laser Coherence Facts
Linewidth is FWHM of optical spectrum
Narrower linewidth = longer coherence length
Higher power generally reduces linewidth
Quantum noise sets fundamental limit
Technical noise often dominates in practice
Q-factor = ν/Δν measures spectral purity
Understanding Laser Linewidth and Bandwidth
What is Laser Linewidth?
Laser linewidth measures how much a real laser deviates from perfect monochromaticity. It's defined as the full width at half maximum (FWHM) of the optical spectrum, quantifying the spread of frequencies in the laser output around the central frequency.
Quantum vs Technical Noise
- •Quantum noise: Fundamental limit from spontaneous emission
- •Technical noise: Cavity vibrations, temperature fluctuations
- •Mode competition: Multiple longitudinal modes
- •Phase noise: Random phase fluctuations
Key Formulas
- Δν = (π × h × ν × Γ²) / P
- Lc = c / Δν
- Q = ν / Δν
- Δν = c/(λ₀-Δλ/2) - c/(λ₀+Δλ/2)
- Δν: Laser linewidth (Hz)
- h: Planck constant (6.626×10⁻³⁴ J⋅s)
- ν: Laser frequency (Hz)
- Γ: Cavity linewidth (Hz)
- P: Laser power (W)
- Lc: Coherence length (m)
Applications and Importance
Interferometry
Ultra-narrow linewidths enable coherent interference over vast distances, crucial for gravitational wave detection and precision measurements.
Spectroscopy
Narrow linewidth lasers resolve fine spectral features in atomic and molecular systems, enabling high-resolution spectroscopic analysis.
Optical Communication
Low phase noise and narrow linewidths enable coherent optical communication systems with high data rates and long transmission distances.