Laser Linewidth and Bandwidth Calculator
Convert between wavelength linewidth and frequency bandwidth
How to Use This Calculator
Select Calculation Type
Choose whether you want to convert from wavelength linewidth to frequency bandwidth, or from frequency bandwidth to wavelength linewidth.
Enter Wavelength
Input the central wavelength of the laser in meters. For example, 532 nm = 0.000000532 m.
Enter Linewidth or Bandwidth
Input either the wavelength linewidth (Δλ) in meters or the frequency bandwidth (Δν) in Hz, depending on your selection.
Calculate
Click the "Calculate" button to get the converted value.
Formulas
Linewidth to Bandwidth
Δν = (c/λ²) × Δλ
Bandwidth to Linewidth
Δλ = (λ²/c) × Δν
Where:
- Δν = Frequency bandwidth (in Hz)
- Δλ = Wavelength linewidth (in meters)
- λ = Central wavelength (in meters)
- c = Speed of light = 299,792,458 m/s
Example Calculation:
For a 532 nm laser with 1 pm linewidth:
λ = 0.000000532 m
Δλ = 0.000000000001 m (1 pm)
Δν = (299,792,458 / (0.000000532)²) × 0.000000000001
Δν ≈ 1.06 GHz
About Laser Linewidth and Bandwidth Calculator
Laser linewidth and bandwidth are related measures of spectral width. Linewidth is the width in wavelength units, while bandwidth is the width in frequency units. They're related through the speed of light and the central wavelength. This calculator converts between these two representations, which is essential for understanding laser spectral properties, coherence length, and suitability for applications like spectroscopy, optical communications, and precision measurements.
When to Use This Calculator
- Laser Characterization: Convert between wavelength and frequency representations of spectral width
- Spectroscopy: Understand spectral resolution requirements
- Optical Communications: Calculate bandwidth requirements and channel spacing
- Research: Analyze laser spectral properties
- Educational Purposes: Learn about the relationship between wavelength and frequency
Why Use Our Calculator?
- ✅ Bidirectional Conversion: Convert from linewidth to bandwidth or vice versa
- ✅ Instant Results: Get accurate conversions immediately
- ✅ Multiple Units: Results displayed in base units and convenient units (MHz, pm)
- ✅ Educational: Includes formula explanations and worked examples
- ✅ 100% Free: No registration or payment required
Common Applications
Optical Communications: In wavelength-division multiplexing (WDM), bandwidth determines channel spacing. Understanding the relationship between linewidth and bandwidth helps design systems with appropriate channel spacing.
Spectroscopy: Narrow linewidths are essential for high-resolution spectroscopy. Converting between wavelength and frequency representations helps understand spectral resolution requirements.
Interferometry: Linewidth relates to coherence length, which is crucial for interferometric measurements. Understanding bandwidth helps predict coherence properties.
Tips for Best Results
- Use consistent units (meters for wavelength and linewidth, Hz for bandwidth)
- Remember that linewidth and bandwidth are inversely related at the same wavelength
- For narrow linewidths, bandwidth is approximately constant across visible spectrum
- Linewidth is typically measured as full-width at half-maximum (FWHM)
- Single-frequency lasers have very narrow linewidths (kHz to MHz range)
- Broadband lasers have wide linewidths (nanometers) and large bandwidths
Frequently Asked Questions
What's the difference between linewidth and bandwidth?
Linewidth is the spectral width measured in wavelength units (meters, nanometers), while bandwidth is measured in frequency units (Hz, MHz). They're different ways of expressing the same spectral property, related through the speed of light.
Why does the conversion depend on wavelength?
The relationship between wavelength and frequency is nonlinear (ν = c/λ). A fixed wavelength spread corresponds to different frequency spreads at different wavelengths. Near the same wavelength, shorter wavelengths have larger frequency bandwidths for the same linewidth.
What is a typical laser linewidth?
Single-frequency lasers can have linewidths from kHz to MHz (very narrow). Diode lasers typically have linewidths of 1-100 MHz. Broadband lasers can have linewidths of nanometers. The exact value depends on the laser type and operating conditions.
How does linewidth affect coherence?
Narrower linewidths correspond to longer coherence times and coherence lengths. The coherence length is approximately c/(π × Δν), where Δν is the frequency bandwidth. This is important for interferometry and holography applications.
Can I use this for non-laser sources?
Yes, the formulas apply to any light source, not just lasers. However, the calculator is optimized for laser applications where narrow linewidths are common. For broadband sources, the conversion still works but may require larger numbers.