# Laser Pulse Energy, Peak Power and Fluence Calculator

> Source: https://netray.co/tools/laser-pulse-energy-peak-power-fluence-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Turn average power, repetition rate, pulse width and spot size into pulse energy, peak power, peak fluence and peak irradiance.

## Category

industry-templates

## Industry

Photonics and Optics Manufacturing

## Audience

- Laser process engineer
- Optical coating engineer
- Photonics test engineer

## Tool

**Kind:** calculator

**Inputs:**

#### Average power

**Key:** p

**Type:** number

**Default:** 20

**Min:** 0

**Step:** 0.5

**Unit:** W

#### Repetition rate

**Key:** rate

**Type:** slider

**Default:** 50

**Min:** 1

**Max:** 500

**Step:** 1

**Unit:** kHz

#### Pulse width (FWHM)

**Key:** tau

**Type:** number

**Default:** 10

**Min:** 0.0001

**Step:** 0.5

**Unit:** ns

**Help:** Enter femtosecond or picosecond pulses as ns, for example 300 fs is 0.0003 ns.

#### Pulse shape factor

**Key:** shape

**Type:** select

**Default:** 0.94

**Options:**

##### Gaussian (0.94)

**Value:** 0.94

##### Rectangular (1.00)

**Value:** 1

##### Sech squared (0.88)

**Value:** 0.88

#### Spot diameter (1/e2)

**Key:** spot

**Type:** number

**Default:** 30

**Min:** 0.1

**Step:** 1

**Unit:** um

**Outputs:**

#### Pulse energy

**Key:** e_uj

**Expr:** p / rate * 1000

**Format:** decimal

**Primary:** true

**Description:** uJ. Average power divided by repetition rate.

#### Peak power

**Key:** pk_kw

**Expr:** shape * e_uj / tau

**Format:** decimal

**Primary:** true

**Description:** kW. Pulse energy times shape factor divided by FWHM width.

#### Peak fluence

**Key:** fl

**Expr:** 2 * (e_uj * 0.000001) / (pi * pow(spot * 0.00005, 2))

**Format:** decimal

**Description:** J/cm2 at beam center for a Gaussian spot: 2E / (pi w^2).

#### Peak irradiance

**Key:** irr

**Expr:** 2 * shape * (e_uj * 0.000001) / (pi * pow(spot * 0.00005, 2)) / (tau * 0.000000001) / 1000000000

**Format:** decimal

**Description:** GW/cm2 at the center of the spot.

**Chart:**

#### Peak power (kW) vs repetition rate (kHz)

**Type:** line

**X:** rate

**From:** 1

**To:** 500

**Steps:** 40

**Series:**

- pk_kw

**Disclaimer:** Uses a Gaussian spatial profile and an idealized temporal shape. Compare to the damage threshold of your optics at the same pulse width, wavelength and repetition rate.

## Content

**Intro:** Pulsed laser datasheets quote average power while processes and optics damage thresholds are set by pulse energy, peak power and fluence. This calculator converts between them in one pass.

**Sections:**

#### How to use the calculator

**Body:** Enter the average power, repetition rate, pulse width at full width half maximum, the temporal shape and the 1/e2 spot diameter at the work plane or optic. Pulse energy is average power divided by repetition rate. Peak power uses a shape factor that accounts for the fact that a Gaussian pulse has a higher peak than a flat one of equal energy and width. The sweep chart shows how peak power collapses as repetition rate rises at constant average power.

**Bullets:**

- Use ns for all pulse widths; type 0.0003 for 300 fs.
- Check the spot diameter on the surface you care about, not at the focus.
- For multi-pulse damage, compare fluence to the threshold for N pulses, not single-shot.

#### Formulas

**Body:** Pulse energy E = P / f. Peak power Ppk = k E / tau, where k is 1 for a rectangular pulse, about 0.94 for a Gaussian pulse and about 0.88 for sech squared. Peak fluence for a Gaussian spot of 1/e2 radius w is 2E / (pi w^2). Peak irradiance is peak fluence times the shape factor divided by pulse width. Unit tracking matters: microjoules divided by nanoseconds yields kilowatts, which the calculator applies automatically.

#### Reading the result

**Body:** A 20 W, 50 kHz, 10 ns laser delivers 400 uJ per pulse and about 38 kW peak. Focused to a 30 um spot the peak fluence is of the order of 100 J/cm2, far above most coating thresholds, so such a beam should never be allowed to hit an optic at that focus. Moving to 500 kHz at the same average power drops pulse energy tenfold, and the same optics might be safe. This is why a laser repetition rate change must trigger an optics review.

#### Common mistakes

**Body:** Quoting laser damage thresholds without pulse width and wavelength is meaningless, because threshold fluence scales roughly with the square root of pulse width in the nanosecond to picosecond range. Another mistake is using the average spot area when the beam has hot spots; beam profilers show peaks well above Gaussian predictions. Finally, many users forget that fluence at an optic downstream of focus is lower than at the focus: calculate at each element.

**Cta:** Netray can help tie laser setpoints and incident logs to your ERP maintenance and quality modules so optic changes and process parameters stay on one record.

**Faq:**

#### What is the difference between fluence and irradiance?

**Answer:** Fluence is energy per area (J/cm2) delivered by a pulse. Irradiance is power per area (W/cm2). For a pulse, irradiance is fluence divided by pulse duration. Damage thresholds use fluence for ns pulses and often irradiance concerns for ultrafast pulses.

#### Why do I enter the pulse width in ns?

**Answer:** To keep a single unit system. Divide femtoseconds by 1,000,000 and picoseconds by 1,000 to get ns. The tool then returns peak power in kW, which stays readable for ns pulses and is multiplied accordingly for ultrafast pulses.

#### Is the 0.94 shape factor right for my laser?

**Answer:** It is the ratio of peak power to E over FWHM for a Gaussian pulse. For a real laser with a measured waveform, integrate the oscilloscope trace or use the rectangular option as a conservative estimate when peak is not critical.

#### Does this include beam ellipticity?

**Answer:** No. For an elliptical spot with radii wx and wy, replace pi w squared by pi wx wy. You can enter the geometric mean diameter in the spot field as a close approximation.

## Search terms

laser pulse energy calculator, peak power calculator laser, laser fluence calculator, j/cm2 laser calculator, pulse energy from average power, peak irradiance gw/cm2, laser damage threshold fluence, pulsed laser calculator

---
Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json