Assessment of Laser Performance Parameters

It’s not the appearance but the parameters that determine whether a laser is good or not.

Laser sounds sci-fi, yet it has long been integrated into our daily lives:

Metal cutting in factories, logo marking on the back of mobile phones, myopia surgery in hospitals, and data transmission via optical fiber broadband—all of these rely on lasers.

So here comes the question: How exactly do we evaluate the performance of a laser?

Today, we will break down the 7 most critical parameter indicators of a laser.

01  What Is a Laser?

There are many types of lasers (solid-state, gas, semiconductor, fiber, etc.), but they all follow the same working principle:

A pump source injects energy into the active medium, enabling it to emit light in an organized manner inside an optical resonant cavity, and finally output a beam of light with extremely high directionality, spectral purity and energy density.

Different types of lasers focus on entirely different parameters.

For example, industrial cutting prioritizes output power, precision marking values beam quality, while scientific research focuses on linewidth and timing jitter.

02  7 Core Indicators You Must Know for Lasers

1. Beam Quality (M² Factor) — The "Sharpness of a Laser Blade"

Simple explanation:

The closer the M² value is to 1, the closer the laser beam is to perfection. After focusing, the light spot is extremely small, just like an ultra-sharp scalpel.

The higher the M² value, the faster the beam diverges, and the focused spot becomes larger—just like cutting with a blunt knife.

Impact on applications:

• M² ≤ 1.2 → Precision micro-processing, high-quality cutting

•  Relatively high M² → Rough machining, welding, surface treatment

In short: The higher the precision requirement, the more critical the M² factor is.

2. Brightness / BPP — Comprehensive Performance

Brightness refers to the output power per unit area and per unit solid angle.

A more practical parameter is BPP (Beam Parameter Product). The smaller the value, the finer and straighter the laser beam, with more concentrated energy.

Practical significance:

For two lasers with the same output power, the one with a smaller BPP can maintain high energy density over a longer distance, making it suitable for remote welding, deep penetration welding and high-speed cutting.

3. Power Stability — A Qualified Laser Maintains Stable Output

Will the output power of a laser fluctuate up and down during operation?

This indicator is usually expressed as ±X% (e.g. ±1%).

Why it matters:

In scenarios such as micro-processing, semiconductor annealing and medical aesthetics, even a 1% power fluctuation may lead to product scrap or poor treatment results.

A high-quality laser keeps power fluctuation within ±1% during 8-hour continuous operation.

4. Pulse Characteristics — The "Rhythm" of Pulsed Lasers

For pulsed lasers (not continuous-wave lasers), four key parameters need to be evaluated:

• Pulse Width: Duration of a single pulse.Shorter pulses (femtosecond/picosecond level) → smaller thermal impact → realize cold processing, ideal for brittle materials and precision drilling.

• Pulse Energy: Energy carried by a single pulse.Higher energy → suitable for cleaning, drilling and impact strengthening.

•  Peak Power = Pulse Energy / Pulse WidthUltrashort pulses can generate extremely high peak power (GW or even TW level), applied to internal modification of transparent materials.

•  Timing Jitter: Deviation between the actual arrival time of a pulse and the ideal time. Low jitter (<1ps) is a rigid requirement for scientific research such as synchronous pumping and ultrafast detection.

Easy mnemonic: Shorter pulse width means lower thermal impact; higher pulse energy means stronger cutting ability; lower jitter means higher accuracy.

5. Linewidth — The "Purity" of Laser Spectrum

The narrower the linewidth, the purer the laser wavelength.Common units: MHz or pm (picometer).

Practical impact:

• Narrow linewidth (<1 kHz) → Extremely long coherence length → Applied to gravitational wave detection, high-precision interferometry and atomic clocks.

•  Wide linewidth → Only suitable for ordinary marking and cutting.

6. Electro-Optical Efficiency — The Key to Energy Saving

Formula:

Electro-Optical Efficiency = (Laser Output Power / Input Electric Power) × 100%

Practical significance:

The electro-optical efficiency of fiber lasers can reach 40%~50%. That means to output 1000W laser power, it only consumes 2000~2500W electric power.

Old-fashioned lamp-pumped solid-state lasers only have an efficiency of 3%~5%, with most electricity converted into heat.

Higher efficiency = lower electricity cost, less cooling equipment investment and higher operational reliability. It is a core economic indicator for industrial mass production.

7. Pointing Stability — No Deviation During Long-Term Operation

Measured in microradians (μrad).

Simply put: Whether the laser emission direction drifts after hours of continuous operation.

Key application scenarios:

Wafer cutting, long-distance remote sensing, and systems requiring complex optical path transmission.

Poor pointing stability will cause gradual deviation in processing position, resulting in a large number of defective products.

Premium lasers control pointing drift within tens of microradians, delivering rock-solid stability.

03  Key Indicators for Different Application Scenarios