Pulse energy calculator

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How it works?

Most laser power meters measure the "Average Power" over time. However, for pulsed lasers, the energy is concentrated into brief bursts. To find the energy of a single burst, we divide the total power by the number of pulses per second.

E = Pavg / frep Pulse Energy Formula

Where:

  • E : Pulse Energy (Joules).
  • Pavg : Average Power (Watts).
  • frep : Repetition Rate (Hertz).

Quick Reference

  • Low Rep Rate = Higher Pulse Energy (for the same average power).
  • High Rep Rate = Lower Pulse Energy (energy is spread out).
  • To increase ablation/cutting, you usually need higher Pulse Energy, not just average power.

Why calculate Pulse Energy?

In laser materials processing, Average Power is often a misleading metric. Two lasers can both have 10 Watts of power, but if one pulses once per second (10 Joules/pulse) and the other pulses a million times per second (10 microjoules/pulse), they will have vastly different effects on a material.

Typical Pulse Energies by Application

Laser Application Typical Energy Typical Rep Rate
LIDAR 1 µJ - 100 µJ 10 - 100 kHz
Metal Marking 0.5 mJ - 1 mJ 20 - 80 kHz
Tattoo Removal 200 mJ - 1 J 1 - 10 Hz
Laser Cleaning 10 mJ - 100 mJ 10 - 50 kHz
Nuclear Fusion (NIF) 2 MegaJoules 1 Shot / Day

Why Repetition Rate Matters

1. The "Hammer" Analogy

Pulse Energy is the weight of the hammer; Rep Rate is how fast you swing it. A light hammer swung fast (High Rep, Low Energy) is good for polishing. A heavy sledgehammer swung slowly (Low Rep, High Energy) destroys concrete.

2. Heat Accumulation

If the rep rate is too high, the material cannot cool down between pulses, causing a large Heat Affected Zone (HAZ). Lowering the rep rate maintains high energy per pulse while allowing for "cold" ablation.

3. Damage Thresholds

Optics are rated by Fluence ($J/cm^2$). A high-energy pulse can shatter a lens even if the average power is very low. You must calculate the Joules per pulse to select safe optics.

4. Frequency Doubling

Non-linear crystals (SHG) require high peak intensity to work efficiently. A 1mJ pulse converts to green light much better than a 1µJ pulse, even if the average power is the same.

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Related Engineering Tools

Peak Power

Use your Energy (J) and Pulse Width to find Peak Wattage.

 dBm to Watts

Convert logarithmic power readings to linear Watts.

 Laser Spot Size

Combine Pulse Energy with Area to get Fluence ($J/cm^2$).