Laser Pulse Calculator

A laser pulse is a short, intense burst of light energy emitted by a laser over a very brief time interval. Pulsed lasers turn on and off rapidly, producing a train of pulses characterised by their duration, repetition rate, and energy per pulse. They are widely used in applications like material processing, medical procedures, and scientific research where high peak power is needed.

Average power is the total energy delivered over a long time period, while peak power is the instantaneous power at the top of each pulse. Because energy is compressed into very short pulses, peak power can be orders of magnitude higher than average power. For example, a 1 W average power laser firing 10 ns pulses at 1 kHz delivers 1 mJ per pulse but reaches a peak power of roughly 100 kW.

Pulse energy equals the average power divided by the repetition rate: E = P_avg / f. For example, if your laser has 1 W of average power and fires at 1 kHz, each pulse carries 1 mJ of energy. This assumes all energy is delivered in discrete pulses with no CW background.

A rectangular pulse assumes constant power over the full pulse duration, while Gaussian and sech² (hyperbolic secant squared) pulses have a bell-shaped power envelope. The peak sits higher than the average over the pulse, so correction factors of approximately 0.94 (Gaussian) and 0.88 (sech²) are applied to the pulse duration when computing peak power, resulting in higher peak power values for the same energy and nominal pulse width.

Duty cycle is the fraction of time the laser is 'on', calculated as the product of pulse duration and repetition rate: D = T × f × 100%. A 10 ns pulse at 1 kHz repetition rate gives a duty cycle of 0.001%, meaning the laser is active for only a tiny fraction of the total time. Low duty cycles allow very high peak powers while keeping average power low.

Pulse separation (also called the period or round-trip time between pulses) is simply the reciprocal of the repetition rate: T_sep = 1 / f. At 1 kHz repetition rate, pulses are separated by 1 millisecond. This tells you the gap between consecutive pulses in the pulse train.

Intensity is power divided by beam area. Average intensity = average power / beam area, and peak intensity = peak power / beam area. The beam area is calculated from the spot diameter assuming a circular cross-section: A = π × (d/2)². Knowing the spot size is essential when assessing whether your laser exceeds the damage threshold of an optical component or material.

The calculator accepts flexible unit inputs for each parameter. Average power can be entered in kW, W, mW, µW, or nW. Pulse duration can be specified in fs, ps, ns, µs, or ms. Repetition rate accepts THz, GHz, MHz, kHz, or Hz. Spot diameter accepts µm, mm, or cm. All values are internally converted to SI base units (watts, seconds, hertz, meters) before calculation.