Why Laser Beam Compression Matters for Laser Engraving Quality

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If you’ve been following the consumer laser engraving market lately, you’ve probably noticed an intense race toward higher wattages. Everyone is talking about 20W, 40W, and even 80W modules. But as any experienced optical engineer or seasoned hobbyist will tell you, power is only half the equation. The real magic—the key to crisp lines, deep gradients and perfect photo engraving—is in how you manage that power.

Today, we need to talk about laser beam compression.

In this session, we’ll look at the physics of laser spot size, the metrics we use to evaluate laser beam quality, and why the choice of optical compression can make or break your final product.

This analysis also applies to other semiconductor laser applications, such as 905nm LiDAR lasers, 9XXnm/808nm pump sources, and visible red, green, and blue semiconductor lasers used in stage lighting and projection industries.

1. Introduction to the Optical Collimation Solutions

Consumer-grade laser modules generally range from 1.6W to 80W in power output. Entry-level low-power products account for the largest sales volume, while higher-power models are more expensive and have lower sales volumes. However, the profit margin trend is the opposite — high-power laser modules usually generate significantly higher profits per unit.

Currently, there are three mainstream collimation solutions. This article focuses on the first type:

1. Plano-Convex Aspheric Lens Collimation (FAC Technology)

a. How it Works

In the semiconductor industry, this is known as Fast Axis Collimation, or FAC.

This solution has a relatively high cost but delivers excellent collimation performance, making it suitable for applications with extremely high beam quality requirements.

It is primarily used in high-power industrial laser systems, such as 200W, 300W, or even multi-combined kilowatt-level industrial applications, including industrial welding and cutting — especially for copper-containing materials.

Metals such as copper and gold have an absorption rate of less than 5% for near-infrared lasers (such as 1064nm), which results in low processing efficiency and severe spatter during machining. In contrast, 450nm blue lasers exhibit significantly higher absorption in copper — often an order of magnitude higher than 1064nm infrared lasers — greatly improving energy utilization efficiency.

When using blue lasers for copper welding, stable keyhole formation can be achieved in deep-penetration welding mode, reducing porosity and spatter while maintaining excellent weld consistency. This makes the technology particularly suitable for high-precision applications such as power batteries and motor windings.

Blue laser systems can also be applied in metal laser sintering for additive manufacturing and laser weeding technologies. These topics deserve separate discussion in the future, as ultra-high-precision laser processing has strong long-term potential.

b. Initial Laser Beam Characteristics

The original laser beam emitted by a semiconductor laser diode typically has:

• A very large divergence angle along the Y-axis
• A relatively small divergence angle along the X-axis

c. Aspheric Collimation Principle

After collimation using an aspheric lens:

• Optical aberrations are minimized
• Beam compression performance becomes highly optimized

d. Evaluation of the FAC Solution

Advantages

1. Excellent beam quality with minimal stray light
2. Outstanding collimation performance

Disadvantages

1. Relatively high cost
2. More suitable for industrial-grade applications with extremely high engraving or processing quality requirements

e. Applications in Consumer Laser Engraving

In the consumer laser engraving market, standard gantry-style machines such as 1.6W, 3.5W, 5W, and 10W models rarely use FAC collimation solutions. Only some galvanometer-based laser systems adopt this approach, where the beam is collimated before entering the field lens system.

Overall, the FAC (Fast Axis Collimation) cylindrical/aspheric lens compression solution is not commonly used in consumer-grade laser engraving products unless the product is positioned as a high-end offering.

Because FAC technology is less frequently used in consumer laser engravers, there is relatively limited discussion about it in this field. However, there is much more to explore regarding its applications in other industrial semiconductor laser systems.

2. Fiber Compression (The Balanced Contender)

a. How it Works

Fiber-Lens Beam Compression (Cylindrical Fiber Lens Technology, hereinafter referred to as Fiber Compression) solutions are popular because fiber rod lenses are relatively inexpensive to manufacture and integrate. After applying anti-reflective coatings on both sides, the fiber can function as a cylindrical lens.

Currently, major laser diode manufacturers such as OSRAM and Nichia Corporation generally do not provide factory-integrated fiber-compressed collimation solutions. As a result, some companies in China still profit from secondary processing by disassembling TO-can packages, extracting the laser chips, and performing their own packaging and optical compression.

However, in my opinion, this situation will likely change as domestic Chinese laser chips continue to improve. Following the common approach of many Chinese manufacturers, domestic chip suppliers will probably begin offering integrated packaging and various factory-level collimation solutions themselves. This would not only improve product diversity and compatibility, but also increase overall profit margins.

b. Optical Analysis of Fiber Compression

Fiber Collimation Characteristics

The fiber collimation structure is illustrated below:

• It is obvious that some stray light still exists
• Complete compression cannot be fully achieved

Advantages

1. By adjusting the position of the optical fiber, the beam spot divergence angle can be controlled
2. Different divergence characteristics can therefore be achieved flexibly

Disadvantages

1. Cylindrical collimation performance is relatively average
2. Achieving extremely precise collimation is difficult
3. In most cases, the beam can only be “roughly collimated”

c. Operating Principle

In the consumer laser engraving industry, 1° or 8° collimation designs are commonly used.

The reason for using an 8° configuration is to make the fast-axis divergence angle closer to the slow-axis (X-axis) divergence angle. Matching these angles simplifies subsequent beam shaping using spherical lenses.

As shown in the 8° collimation example:

• The fast-axis and slow-axis divergence become relatively similar
• The emitted beam remains approximately square-shaped within a certain distance

d. Overall Optical Path

The actual focusing performance is quite good:

• The beam spot is relatively square and well-balanced
• The focusing quality is sufficient for engraving applications

e. Some Non-Technical Thoughts

At present, many TOC laser engraving machine companies are essentially assembly factories with limited technological barriers. In the early stages of the market, when competition was not yet saturated, most companies were still able to make reasonable profits.

However, companies without core proprietary technology are likely to face rapidly increasing profit pressure over the next few years. This trend is especially evident as many companies have recently attracted outside investment, accelerating market consolidation and the classic “80/20” industry effect that will eliminate weaker players.

Simply pursuing the low-end market and obsessively cutting a few dollars of cost is not a sustainable strategy. Once product quality or reputation suffers, recovery becomes extremely difficult — and there are already many examples of this happening in the market.

Looking at the historical development of most industries, major end-product manufacturers eventually integrate vertically into upstream components and technologies. Product stability and reliability are often far more important than saving a few dollars in manufacturing cost.

Personally, I am not particularly optimistic about companies that operate purely as laser source suppliers or simple assembly factories, especially in a market where the entry barrier itself is relatively low.

3. Lens Compression (The Budget Compromise)

a. Aspheric Lens Compression

This is currently the lowest-cost solution for dual-diode beam combining in consumer laser modules, but it also delivers the weakest optical performance.

This type of collimation is commonly seen in:

• Low-cost laser pointers
• Some stage lighting systems

In many cases, manufacturers simply place a large-NA (Numerical Aperture) lens in front of the laser diode to achieve basic collimation.

b. Collimation Performance and Principle

The collimation effect and optical principle are illustrated below.

c. Beam Spot After Collimation

The resulting beam quality is relatively poor:

• The divergence difference between the X and Y axes is extremely large
• Beam symmetry is poor

Comparison:

• Left: Lens compression
• Right: Fiber compression

d. Actual Focusing Performance

Measured focusing results show:

• Very obvious trailing artifacts
• Significant stray light

A noticeable streak or “tail” appears around the focused spot. When engraving high-absorption materials such as wood or leather:

• The spot becomes larger
• Burn marks become more visible
• Engraving quality decreases significantly

This solution is generally only suitable for around 10W power levels. At higher powers, beam control and processing become much more difficult.

e. Detailed Analysis of the Solution

Advantages:

The biggest advantage of this solution is simply its extremely low cost.

Disadvantages

• Poor Collimation Performance: After collimation, the divergence angles in the X and Y directions remain significantly different.
• Additional Beam Expansion Is Required: The X-axis often requires additional beam expansion and correction, increasing overall module size.
• Strong Sensitivity to Lens Decentering: Because short focal-length aspheric lenses are used, the system is highly sensitive to lens eccentricity or misalignment, causing the beam direction to shift easily. At present, some low-cost aspheric lens suppliers offer relatively poor quality control, which negatively affects mass-production yield rates.
• More Optical Adjustment Processes: Using multiple lenses increases optical alignment and calibration steps during production, adding manufacturing cost.
• Obvious Beam Tailing During Focusing: The focused spot exhibits clear trailing artifacts, resulting in visible burn traces and lower engraving quality.
• Difficult to Share Production Lines with High-Power Products: From a manufacturing perspective, this solution is difficult to integrate with higher-power product lines such as 40W or 60W systems, increasing: Production complexity, Material management costs, and Manufacturing overhead.

Overall, this is a compromise-oriented solution.

Today’s low-power consumer engraving market has become extremely price-competitive, with profit margins continuously shrinking. As a result, manufacturers often adopt this low-cost approach despite its obvious optical limitations.

4. Additional Thoughts on Manufacturing and Worker Safety

One more important point worth mentioning:

The more complicated the production and optical alignment process becomes, the longer front-line workers are exposed to blue laser radiation during assembly and calibration.

Many factory workers lack sufficient education or awareness regarding the dangers of laser exposure to the eyes. After working in such environments for a period of time, they may gradually experience worsening vision or eye discomfort. Most simply resign and leave without fully understanding the cause.

The problem is that this type of eye damage is often irreversible. Even after leaving the job, their eyesight does not recover.

In many cases, workers also lack awareness of occupational injury rights related to laser exposure. Unless the vision damage becomes extremely severe, many choose to tolerate it rather than pursue compensation or medical evaluation. They may complain privately about poor factory conditions and then quietly move on.

From both an ethical and business perspective, manufacturers should invest more in protective equipment and safety measures.

Money can always be earned later, but eye damage cannot be undone.

This is especially important for small factories, where a single serious workplace injury incident can result in substantial financial liability.