How do I Measure Laser Bandwidth?

The intensity spectrum of a laser is measured with an optometer.

In photonics, the science and technology of lights, the term bandwidth often refers to the spectral linewidth, or the intensity spectrum of the output of a light source such as a laser beam. Because the intensity of light is equal to the light's power per unit time divided by the area the light encompasses, the measurements can be taken using a ruler and a optometer, a device commonly used by optometrists to test a patient's vision.

Things You'll Need

• White board
• Laser
• Ruler
• Optometer

Instructions

1. Stand the white board opposite the laser.

2. Direct the laser toward the light board, turn it on and shoot a beam of light onto the board.

3. Measure the width of the circle of light emitted onto the board using a ruler.

4. Turn on the optometer and place the device so that the beam of light directly hits the optometer's reading plate. Note the power in watts.

5. Enter the results into the formula for intensity: I = P/(4pi*r^2) where "P" is the watts measured in Step 4 and "r" is the radius measured in Step 3. The result is the laser beam's spectral intensity or bandwidth.

References

• "Laser Spectroscopy: Basic Concepts and Instrumentation;" W. Demtröder; 2003.
• "Light Science: Physics and The Visual Arts;" Thomas D. Rossing; 1999.