How to Expand, Shape, and Steer Laser Beams: Complete Guide to Beam Expanders, Cylindrical Lenses, and Beam Steering Optics

Introduction

Every laser system starts with a beam that is never quite right. Diode lasers output elliptical, highly divergent beams. Solid-state lasers produce circular beams that are still too large for downstream optics. And in nearly every setup, the beam needs to be redirected — folded, raised, or tilted to match the mechanical layout. Without proper beam expansion, shaping, and steering, you end up with clipped apertures, non-uniform intensity profiles, pointing instability, and wasted optical power.

The good news is that beam control is one of the most well-understood areas of applied optics. A small set of components — beam expanders, cylindrical lenses, aspherical lenses, mirrors, and prisms — can transform almost any raw laser output into a beam that matches your application requirements. The challenge is knowing which component to use, in what order, and with what specifications.

This guide walks through the three fundamental operations in laser beam delivery: expansion (changing beam diameter), shaping (correcting ellipticity, circularizing diode beams, and generating line patterns), and steering (redirecting the beam path with mirrors and periscopes). For each operation, we explain the underlying optics, the key specifications to consider, the common mistakes engineers make, and the PhotonEdge components that are purpose-built for these tasks.

Part 1: Beam Expansion — Why and How to Expand a Laser Beam

Why Expand a Beam?

Beam expansion serves several critical purposes in laser systems:

• Reduce divergence: A larger beam diameter means lower angular divergence (divergence scales inversely with beam diameter). Expanding a 1 mm beam to 10 mm reduces far-field divergence by 10×. This is essential for long-range applications like LiDAR, free-space communication, and laser ranging.
• Match downstream apertures: Spatial light modulators, galvanometer scanners, and diffractive optical elements have specific input beam diameter requirements. Beam expansion matches the laser output to these apertures without wasting energy.
• Reduce power density on optics: Expanding the beam before it hits a mirror or lens reduces irradiance (W/cm²), protecting downstream optics from laser-induced damage. This is critical in high-power laser systems where mirrors near the laser output face the highest fluence.
• Improve focusing performance: A collimated, expanded beam focused by a lens produces a smaller focal spot. Spot diameter scales with f-number (focal length / beam diameter), so larger input beams yield tighter foci for laser cutting, welding, and microscopy.

Types of Beam Expanders

Beam expanders come in two fundamental designs:

Refractive Beam Expanders (Lens-Based)

Refractive beam expanders use two lenses — a short focal length input lens and a longer focal length output lens — arranged in a Keplerian (with internal focus) or Galilean (no internal focus) configuration. The magnification is the ratio of the output lens focal length to the input lens focal length:

Magnification (M) = f_output / f_input ; Output Diameter = M × Input Diameter

• Galilean expanders use a negative input lens and positive output lens. They are shorter (no internal focus), lighter, and avoid the air breakdown risk at the internal focus point. Preferred for high-power laser systems.
• Keplerian expanders use two positive lenses with an internal focus. The internal focus allows insertion of a spatial filter (pinhole) to clean up beam profile, but introduces a high-power-density point that can cause air breakdown at high energies.

PhotonEdge Laser Beam Expanders are available in 2×, 3×, 5×, and 10× magnification with AR coatings optimized for common laser wavelengths (532 nm, 633 nm, 1064 nm). They provide diffraction-limited performance with wavefront error < λ/4 at the operating wavelength.

Reflective Beam Expanders (Mirror-Based)

For very high power lasers or broadband (wavelength-agile) systems, reflective beam expanders use curved mirrors instead of lenses. They eliminate chromatic aberration and material absorption entirely, making them suitable for ultrafast femtosecond lasers and CO2 laser systems where transmissive optics would be damaged or absorptive.

Beam Expander Selection Criteria

Parameter	What to Check	Why It Matters
Magnification	Must produce output diameter matching downstream aperture	Under-expansion wastes energy; over-expansion clips apertures
Input beam diameter range	Expander must accept your laser's beam diameter	Too large input beam gets clipped at the input lens
AR coating wavelength	Must match laser wavelength (±5%)	Wrong coating causes reflection loss and potential damage
Wavefront quality	< λ/4 for precision work; < λ/2 for general	Poor wavefront degrades focal spot and beam profile
Damage threshold	Must exceed system fluence	Insufficient LIDT causes optic failure

Part 2: Beam Shaping — Circularizing, Line-Generating, and Profile Correction

2.1 The Diode Laser Problem: Elliptical Beams

Diode lasers are the most common laser sources in industrial and scientific systems — used in LiDAR, barcode scanning, flow cytometry, pump sources for solid-state lasers, and countless other applications. But diode lasers have a fundamental beam quality issue: the beam exiting the semiconductor junction is highly astigmatic and elliptical.

The fast axis (perpendicular to the junction) has a very short emission aperture (~1 μm) and diverges rapidly (30–40° half-angle). The slow axis (parallel to the junction) has a wider aperture (~100–200 μm) and diverges more slowly (5–10° half-angle). The result is an elliptical beam with an aspect ratio of 2:1 to 4:1, and different divergence in each axis.

This ellipticity causes problems: non-uniform intensity distribution, asymmetric focal spots, and inefficient coupling into circular apertures like fibers and scanners.

2.2 Anamorphic Beam Expansion with Cylindrical Lens Pairs

The standard solution for circularizing diode laser beams is anamorphic beam expansion using a pair of cylindrical lenses. The concept is straightforward:

1. Place a cylindrical lens oriented to affect only the fast axis of the beam
2. Expand the fast axis to match the slow axis diameter
3. The result is a circular beam with matched divergence in both axes

The expansion ratio needed depends on the diode laser's fast-axis and slow-axis divergence angles. For a typical diode with 36° fast-axis and 8° slow-axis divergence, you need approximately 4.5× magnification in the fast axis:

Expansion ratio = θ_fast / θ_slow = 36° / 8° = 4.5×

PhotonEdge BK7 Plano-Convex Cylindrical Lenses are available in focal lengths from 20 mm to 500 mm, making it straightforward to design anamorphic pairs for any standard diode laser. For UV diode lasers (below 350 nm), use UV Fused Silica Plano-Convex Cylindrical Lenses to ensure adequate transmission.

2.3 Line Generation for Scanning and Illumination

Many applications require a laser line rather than a point: time-delay-integration (TDI) inspection, laser triangulation sensors, structured light projection, and laser illumination for machine vision. A single plano-concave cylindrical lens diverges the beam in one axis, creating a line at a given working distance. The line width is determined by the beam diameter in that axis at the working distance.

For more uniform line profiles, a Powell lens or a multi-element cylindrical lens relay system is preferred, but for many industrial applications a single cylindrical lens provides adequate line uniformity at much lower cost.

2.4 Aspherical Lenses for Diode Collimation

While cylindrical lenses correct the ellipticity, you still need to collimate the highly divergent beam in both axes. Aspherical lenses are the standard choice for collimating diode laser output because they eliminate spherical aberration that would otherwise degrade beam quality.

A typical diode collimation assembly uses:

• A fast-axis collimator (FAC) — a high-NA aspherical lens or cylindrical lens that collimates the fast axis
• A slow-axis collimator (SAC) — a cylindrical lens that collimates the slow axis
• An anamorphic pair — to circularize the beam after both axes are collimated

PhotonEdge Aspherical Lenses are available with AR coatings for common diode wavelengths (635 nm, 780 nm, 808 nm, 980 nm, 1064 nm) and numerical apertures up to 0.55, covering virtually all standard laser diode collimation requirements.

Part 3: Beam Steering — Mirrors, Prisms, and Periscopes

3.1 Flat Mirrors for Beam Deflection

The simplest way to redirect a laser beam is with a flat mirror. A single mirror at 45° deflects the beam 90°. Two mirrors create a periscope (offset the beam vertically or horizontally). Three mirrors form a beam relay that preserves beam direction while shifting position.

The choice of mirror coating depends on the laser wavelength and power:

• Protected Aluminum Mirrors: >90% reflectance from UV (300 nm) through NIR. Good general-purpose choice for low-to-medium power systems. The protective overcoat prevents oxidation that degrades UV reflectance.
• Laser Line High Reflected Mirrors: >99.5% reflectance at specific laser wavelengths (532 nm, 1064 nm, etc.). Dielectric coatings optimized for maximum reflectance at the target wavelength. Essential for laser resonators and high-efficiency beam delivery.
• Broadband Dielectric Mirrors: >99% reflectance over a wide wavelength range. Used in tunable laser systems, ultrafast lasers, and multi-wavelength setups where a single-wavelength HR coating would be inadequate.

3.2 Periscopes Using Right-Angle Prisms

For precision beam steering, BK7 Right-Angle Prisms offer advantages over flat mirrors. When used in total internal reflection (TIR) mode, a right-angle prism deflects the beam exactly 90° with no coating required — the reflection efficiency approaches 100%. Unlike mirrors, prisms cannot tilt or de-rotate over time because the 90° angle is fixed by the glass geometry.

Two right-angle prisms arranged in a periscope configuration offset the beam vertically while maintaining its horizontal direction. This is commonly used to:

• Route beams between optical breadboard levels
• Clear obstacles in the beam path
• Adjust beam height to match the input aperture of downstream optics

For UV laser systems, use UV fused silica right-angle prisms instead of BK7 to maintain transmission below 350 nm.

3.3 Optical Mounts for Beam Steering Stability

Even the best mirror or prism is useless if the mount drifts. Vibration, thermal cycling, and mechanical creep all cause pointing instability over time. Key mount specifications for laser beam steering:

• Kinematic adjustment: Fine-pitch screws with resolution of 1-2 arcminutes per division for precise angular alignment
• Locking mechanisms: After alignment, locks prevent drift from vibration. Some mounts use push-pull screws; others use locking nuts.
• Thermal stability: Invar or low-CTE mounts for systems operating over temperature ranges

PhotonEdge 360° Rotating Waveplate/Polarizer Mounts provide precision rotation for polarization optics, while standard kinematic mirror mounts (available from optical component suppliers) handle beam steering mirror alignment.

Part 4: System Design — Putting It All Together

Typical Beam Delivery Chain

A complete laser beam delivery system typically follows this sequence:

1. Source collimation: Aspherical lens collimates the raw diode output
2. Beam circularization: Anamorphic cylindrical lens pair corrects ellipticity
3. Beam expansion: Beam expander increases diameter for reduced divergence
4. Beam steering: Mirror or prism pair redirects beam to the target
5. Final focusing: Plano-convex or achromatic lens focuses beam to the working spot

Each stage must be designed in sequence — the output of one stage is the input to the next. Start by defining the final focusing requirements (spot size, working distance), then work backwards through the beam delivery chain to select expanders, shapers, and steering optics.

Design Example: Diode Laser Marking System

Consider a 808 nm diode laser (fast-axis divergence 36°, slow-axis 8°, initial beam 1 mm × 3 mm) used for laser marking with a 200 mm focal length f-θ lens requiring a 6 mm input beam:

• Step 1 — Collimate: 3 mm FL aspherical lens (NA 0.55) collimates fast axis
• Step 2 — Circularize: 4.5× anamorphic pair using 25 mm and 112.5 mm cylindrical lenses
• Step 3 — Expand: 2× beam expander (1064 nm AR coating, compatible at 808 nm) brings beam to 6 mm
• Step 4 — Steer: Protected aluminum mirror at 45° directs beam to marking head
• Step 5 — Focus: 200 mm f-θ lens produces ∼20 μm spot

Part 5: Five Common Beam Delivery Mistakes

1. Using a Spherical Lens to Collimate a Diode Laser

A spherical lens cannot independently control divergence in the fast and slow axes. The fast axis will be over-collimated (or under-collimated) while the slow axis is the opposite. The result is an asymmetric, unusable beam profile. Always use an aspherical lens or separate FAC/SAC cylindrical lenses for diode laser collimation.

2. Ignoring Beam Expander Input Diameter Limits

If the input beam is too large for the expander's input lens aperture, the beam gets clipped, causing diffraction rings and power loss. Always verify that the beam expander's input aperture exceeds your beam diameter by at least 20% margin.

3. Using Bare Aluminum Mirrors for UV Systems

Bare aluminum oxidizes rapidly in air, forming a transparent oxide layer that changes the reflectance over time. For UV systems where reflectance margins are already tight, this oxidation can push total system throughput below acceptable levels. Always use protected aluminum mirrors or protected silver mirrors for UV through visible applications.

4. Forgetting That Cylindrical Lenses Have an Axis

Cylindrical lenses have optical power in only one direction. If the cylindrical axis is misaligned by even 1°, the beam will develop astigmatism or the circularization will be imperfect. Use precision rotation mounts and verify alignment with a beam profiler, not just visual inspection.

5. Overlooking Back-Reflections from Beam Expanders

Each air-glass surface in a beam expander reflects a small amount of light back toward the source. In laser systems with optical feedback sensitivity (especially single-mode diode lasers), even -30 dB back-reflection can cause mode hopping and intensity noise. Use beam expanders with optimized AR coatings (R < 0.2% per surface) and consider adding an optical isolator after the laser source.

Component Selection Quick Reference

Operation	Component	PhotonEdge Product	Key Spec
Beam expansion	Beam expander	Laser Beam Expanders	2×-10×; AR at laser wavelength
Beam circularization	Cylindrical lens pair	BK7 PCyl Lenses	Match f-ratio to divergence ratio
Diode collimation	Aspherical lens	Aspherical Lenses	NA matched to diode divergence
Line generation	Plano-concave cylindrical	BK7 PCcyl Lenses	FL determines line angle at working distance
90° beam deflection	Mirror or prism	Al Mirrors / RA Prisms	Coating R% at laser wavelength
Beam offset (periscope)	Two mirrors/prisms	RA Prism pair	Match aperture to beam diameter
Precision rotation	Kinematic mount	360° Rotation Mount	Angular resolution, locking mechanism

PhotonEdge Beam Delivery Optics Portfolio

• Laser Beam Expanders — 2× to 10× magnification, AR coated for common laser lines
• BK7 Plano-Convex Cylindrical Lenses — For anamorphic beam shaping and line generation
• UV Fused Silica Cylindrical Lenses — For UV laser beam shaping below 350 nm
• Aspherical Lenses — High-NA collimation for diode lasers
• BK7 Plano-Concave Cylindrical Lenses — Beam expansion in one axis for line generation
• Protected Aluminum Mirrors — UV through NIR beam steering
• Laser Line HR Mirrors — >99.5% reflectance at specific laser wavelengths
• BK7 Right-Angle Prisms — Precision 90° beam deflection and periscopes
• 360° Rotation Mounts — Precision mounts for polarization and steering optics
• BK7 Plano-Convex Lenses — Final focusing optics for laser material processing

Conclusion

Laser beam expansion, shaping, and steering are not afterthoughts — they are the foundation of any functional laser system. A well-designed beam delivery chain ensures that the right beam diameter, divergence, profile, and direction reach the workpiece or detector. By systematically selecting beam expanders, cylindrical lens pairs, aspherical collimators, steering mirrors, and prisms based on your laser parameters and application requirements, you can transform a raw, imperfect laser output into a precision tool.

PhotonEdge manufactures beam delivery optics with tight tolerances, laser-grade surface quality, and application-specific AR coatings. Whether you are building a diode laser marking system, a LiDAR scanner, a laser microscopy station, or an industrial cutting head, we provide the optical components to make your beam delivery work as intended.

引言

每一台激光器的输出光束都不尽如人意。半导体激光二极管输出椭圆形的、大发散角的光束；固体激光器产生的圆形光束直径可能太大，无法适配下游光学元件；而在几乎所有系统中，光束都需要被重新定向——折叠、抬升或倾斜以匹配机械布局。如果没有适当的光束扩束、整形和转向，您将面临孔径截断、强度分布不均匀、指向不稳定和光功率浪费等问题。

好消息是，光束控制是应用光学中最成熟的领域之一。少量几类元件——扩束器、柱面透镜、非球面透镜、反射镜和棱镜——就能将几乎任何原始激光输出转变为匹配应用需求的光束。挑战在于知道该用哪种元件、以什么顺序使用、需要什么规格参数。

本指南详细介绍激光光束传输中的三个基本操作：扩束（改变光束直径）、整形（校正椭圆度、圆化二极管光束、生成线形图案）和转向（用反射镜和潜望镜改变光束路径）。对于每个操作，我们解释基本光学原理、需要考虑的关键规格、工程师常犯的错误，以及恒鼎光专为此任务设计的元器件。

第一部分：光束扩束——为什么要扩束以及如何扩束

为什么要扩束？

光束扩束在激光系统中起着几个关键作用：

• 减小发散角：较大的光束直径意味着较小的角发散角（发散角与光束直径成反比）。将1 mm光束扩展到10 mm可使远场发散角减小10倍。这对于激光雷达、自由空间通信和激光测距等远距离应用至关重要。
• 匹配下游孔径：空间光调制器、振镜扫描仪和衍射光学元件都有特定的输入光束直径要求。光束扩束使激光输出与这些孔径匹配，避免能量浪费。
• 降低光学元件上的功率密度：在光束到达反射镜或透镜之前扩束可降低辐照度（W/cm²），保护下游光学元件免受激光损伤。这在高功率激光系统中尤为重要——靠近激光输出的反射镜承受最高的通量。
• 改善聚焦性能：被透镜聚焦的准直扩束光产生更小的焦点。光斑直径与f数（焦距/光束直径）成正比，因此更大的输入光束可获得更紧密的焦点，适用于激光切割、焊接和显微镜。

扩束器类型

扩束器有两种基本设计：

折射式扩束器（透镜式）

折射式扩束器使用两个透镜——短焦距输入透镜和长焦距输出透镜——排列成开普勒式（有内部焦点）或伽利略式（无内部焦点）结构。放大倍率为输出透镜焦距与输入透镜焦距之比：

放大倍率 (M) = f_输出 / f_输入 ；输出直径 = M × 输入直径

• 伽利略式扩束器使用负输入透镜和正输出透镜。结构更短（无内部焦点），更轻，避免了高功率时内部焦点处的空气击穿风险。是高功率激光系统的首选。
• 开普勒式扩束器使用两个正透镜，中间有焦点。焦点处可插入空间滤波器（针孔）来改善光束轮廓，但在高能量下会产生高功率密度点，可能导致空气击穿。

恒鼎光激光扩束器提供2×、3×、5×和10×放大倍率，AR镀膜针对常用激光波长（532 nm、633 nm、1064 nm）优化。在工作波长下提供衍射极限性能，波前误差 < λ/4。

反射式扩束器（反射镜式）

对于极高功率激光器或宽波段（波长可调谐）系统，反射式扩束器使用曲面反射镜代替透镜。它们完全消除了色差和材料吸收，适用于超快飞秒激光器和CO2激光系统——在这些系统中透射光学元件会被损坏或吸收能量。

扩束器选型标准

参数	检查内容	重要性
放大倍率	输出直径必须匹配下游孔径	扩束不足浪费能量；过度扩束截断孔径
输入光束直径范围	扩束器必须接受激光的光束直径	输入光束过大在输入透镜处被截断
AR镀膜波长	必须匹配激光波长（±5%）	错误镀膜导致反射损失和潜在损伤
波前质量	精密工作 < λ/4；一般 < λ/2	波前质量差导致焦点和光束轮廓退化
损伤阈值	必须超过系统通量	LIDT不足导致光学元件失效

第二部分：光束整形——圆化、线形生成和轮廓校正

2.1 二极管激光器的问题：椭圆形光束

半导体激光二极管是工业和科学系统中最常用的激光光源——用于激光雷达、条形码扫描、流式细胞术、固体激光器泵浦源及无数其他应用。但二极管激光器有一个根本性的光束质量问题：从半导体结区出射的光束是高度像散的和椭圆形的。

快轴（垂直于结区方向）具有极短的发射孔径（约1 μm），发散迅速（半角30-40°）。慢轴（平行于结区方向）具有较宽的孔径（约100-200 μm），发散较慢（半角5-10°）。结果是一个椭圆光束，长短轴比2:1到4:1，且两个轴的发散角不同。

这种椭圆度会导致问题：强度分布不均匀、焦点不对称、以及无法高效耦合到光纤和扫描仪等圆形孔径中。

2.2 使用柱面透镜对进行变形光束扩束

圆化二极管激光光束的标准解决方案是使用一对柱面透镜进行变形光束扩束（anamorphic beam expansion）。概念很直接：

1. 放置一个柱面透镜，使其仅影响光束的快轴
2. 将快轴扩展到与慢轴直径匹配
3. 结果是两个轴发散角匹配的圆形光束

所需扩束比取决于二极管激光器的快轴和慢轴发散角。对于典型的快轴36°慢轴8°的二极管，快轴需要约4.5倍扩束：

扩束比 = θ_快轴 / θ_慢轴 = 36° / 8° = 4.5×

恒鼎光BK7平凸柱面透镜焦距从20 mm到500 mm可选，可轻松为任何标准二极管激光器设计变形透镜对。对于紫外二极管激光器（350 nm以下），使用紫外熔融石英平凸柱面透镜确保充分透过。

2.3 扫描和照明用线形生成

许多应用需要激光线而非光点：TDI线阵检测、激光三角测量传感器、结构光投影和机器视觉激光照明。单个平凹柱面透镜在一个轴上发散光束，在给定的工作距离处形成一条线。线宽由该轴在工作距离处的光束直径决定。

对于更均匀的线形轮廓，Powell透镜或多元件柱面透镜中继系统是更好的选择，但对于许多工业应用，单个柱面透镜以低得多的成本提供足够的线形均匀度。

2.4 非球面透镜用于二极管准直

虽然柱面透镜校正椭圆度，但您仍需要在两个轴上准直高度发散的光束。非球面透镜是准直二极管激光输出的标准选择，因为它们可消除球差——否则球差会降低光束质量。

典型的二极管准直组件使用：

• 快轴准直器（FAC）——高NA非球面透镜或柱面透镜，准直快轴
• 慢轴准直器（SAC）——柱面透镜，准直慢轴
• 变形透镜对——在两个轴都准直后圆化光束

恒鼎光非球面透镜提供常用二极管波长（635 nm、780 nm、808 nm、980 nm、1064 nm）的AR镀膜，数值孔径高达0.55，覆盖几乎所有标准激光二极管准直需求。

第三部分：光束转向——反射镜、棱镜和潜望镜

3.1 平面反射镜用于光束偏转

重定向激光束最简单的方法是使用平面反射镜。单个45°反射镜将光束偏转90°。两个反射镜形成潜望镜（垂直或水平偏移光束）。三个反射镜形成光束中继，在保持光束方向的同时改变位置。

反射镜镀膜的选择取决于激光波长和功率：

• 保护铝反射镜：从紫外（300 nm）到近红外反射率>90%。适用于低至中功率系统的通用选择。保护膜防止氧化导致的紫外反射率下降。
• 激光线高反射镜：在特定激光波长处反射率>99.5%。针对目标波长最大反射率优化的介质膜镀膜。是激光谐振器和高效率光束传输的必备。
• 宽波段介质反射镜：在宽波长范围内反射率>99%。用于可调谐激光系统、超快激光器和多波长设置——在这些场景中单波长HR镀膜不够用。

3.2 使用直角棱镜的潜望镜

对于精密光束转向，BK7直角棱镜比平面反射镜有优势。当使用全内反射（TIR）模式时，直角棱镜将光束精确偏转90°，无需镀膜——反射效率接近100%。与反射镜不同，棱镜不会随时间倾斜或旋转，因为90°角由玻璃几何形状固定。

两个直角棱镜排列成潜望镜结构，将光束垂直偏移同时保持水平方向不变。这常用于：

• 在光学平台层之间传输光束
• 避开光束路径中的障碍物
• 调整光束高度以匹配下游光学元件的输入孔径

对于紫外激光系统，使用紫外熔融石英直角棱镜代替BK7，以保持350 nm以下的透过率。

3.3 光束转向稳定性的光学支架

即使是最好的反射镜或棱镜，如果支架漂移也毫无意义。振动、热循环和机械蠕变都会导致随时间推移的指向不稳定。激光光束转向的关键支架规格：

• 运动学调节：精密微调螺丝，每格分辨率1-2角分，实现精确角度对准
• 锁定机构：对准后，锁定装置防止振动引起的漂移。一些支架使用推拉螺丝，另一些使用锁紧螺母。
• 热稳定性：对于在温度范围内工作的系统，使用殷钢或低热膨胀系数支架

恒鼎光360°旋转波片/偏振器支架为偏振光学元件提供精密旋转，而标准运动学反射镜支架（可从光学元件供应商处获得）处理光束转向反射镜的对准。

第四部分：系统设计——综合应用

典型光束传输链

完整的激光光束传输系统通常遵循以下顺序：

1. 光源准直：非球面透镜准直原始二极管输出
2. 光束圆化：变形柱面透镜对校正椭圆度
3. 光束扩束：扩束器增大直径以减小发散
4. 光束转向：反射镜或棱镜对将光束重定向到目标
5. 最终聚焦：平凸或消色差透镜将光束聚焦到工作光斑

每个阶段必须按顺序设计——前一个阶段的输出是下一个阶段的输入。首先确定最终聚焦需求（光斑尺寸、工作距离），然后反向通过光束传输链选择扩束器、整形器和转向光学元件。

设计实例：二极管激光打标系统

考虑一个808 nm二极管激光器（快轴发散角36°，慢轴8°，初始光束1 mm × 3 mm），用于激光打标，配备200 mm焦距f-θ透镜，要求6 mm输入光束：

• 步骤1——准直：3 mm焦距非球面透镜（NA 0.55）准直快轴
• 步骤2——圆化：4.5×变形透镜对，使用25 mm和112.5 mm 柱面透镜
• 步骤3——扩束：2× 扩束器（1064 nm AR镀膜，808 nm兼容）将光束扩展到6 mm
• 步骤4——转向：保护铝反射镜45°将光束导向打标头
• 步骤5——聚焦：200 mm f-θ透镜产生约20 μm光斑

第五部分：五个常见的光束传输错误

1. 使用球面透镜准直二极管激光器

球面透镜无法独立控制快轴和慢轴的发散。快轴会被过度准直（或欠准直），而慢轴则相反。结果是产生不对称的、不可用的光束轮廓。对于二极管激光准直，始终使用非球面透镜或分离的FAC/SAC柱面透镜。

2. 忽视扩束器的输入直径限制

如果输入光束对于扩束器的输入透镜孔径来说太大，光束会被截断，产生衍射环和功率损失。始终验证扩束器的输入孔径至少比您的光束直径大20%的余量。

3. 在紫外系统中使用裸铝反射镜

裸铝在空气中迅速氧化，形成透明氧化层，随时间改变反射率。对于反射裕量已经很紧张的紫外系统，这种氧化可能使系统总吞吐量降至可接受水平以下。对于紫外到可见光应用，始终使用保护铝反射镜或保护银反射镜。

4. 忘记柱面透镜有方向轴

柱面透镜仅在一个方向上有光焦度。如果柱面轴即使只偏差1°，光束也会产生像散或圆化不完美。使用精密旋转支架，用光束轮廓仪验证对准——而不是仅靠目视检查。

5. 忽视扩束器的背向反射

扩束器中的每个空气-玻璃表面都会将少量光反射回光源方向。在对光学反馈敏感的激光系统中（尤其是单模二极管激光器），即使-30 dB的背向反射也会导致跳模和强度噪声。使用具有优化AR镀膜（每面R < 0.2%）的扩束器，并考虑在激光源后添加光隔离器。

元件选择快速参考

操作	元件	恒鼎光产品	关键规格
光束扩束	扩束器	激光扩束器	2×-10×；AR镀膜匹配激光波长
光束圆化	柱面透镜对	BK7平凸柱面透镜	焦距比匹配发散角比
二极管准直	非球面透镜	非球面透镜	NA匹配二极管发散角
线形生成	平凹柱面透镜	BK7平凹柱面透镜	焦距决定工作距离处的线角
90°光束偏转	反射镜或棱镜	铝反射镜 / 直角棱镜	镀膜反射率匹配激光波长
光束偏移（潜望镜）	两个反射镜/棱镜	直角棱镜对	孔径匹配光束直径
精密旋转	运动学支架	360°旋转支架	角度分辨率、锁定机构

恒鼎光光束传输光学元件产品组合

• 激光扩束器 — 2×到10×放大倍率，针对常用激光线镀膜
• BK7平凸柱面透镜 — 用于变形光束整形和线形生成
• 紫外熔融石英柱面透镜 — 350 nm以下紫外激光光束整形
• 非球面透镜 — 二极管激光器高NA准直
• BK7平凹柱面透镜 — 单轴扩束用于线形生成
• 保护铝反射镜 — 紫外到近红外光束转向
• 激光线高反射镜 — 特定激光波长反射率>99.5%
• BK7直角棱镜 — 精密90°光束偏转和潜望镜
• 360°旋转支架 — 偏振和转向光学元件的精密支架
• BK7平凸透镜 — 激光材料加工最终聚焦光学元件

结论

激光光束的扩束、整形和转向不是事后考虑——它们是所有功能性激光系统的基础。设计良好的光束传输链确保正确的光束直径、发散角、轮廓和方向到达工件或探测器。通过根据您的激光参数和应用需求系统地选择扩束器、柱面透镜对、非球面准直器、转向反射镜和棱镜，您可以将原始、不完美的激光输出转变为精密工具。

恒鼎光制造具有严格公差、激光级表面质量和应用特定AR镀膜的光束传输光学元件。无论您是在搭建二极管激光打标系统、激光雷达扫描仪、激光显微镜工作站还是工业切割头，我们都提供使您的光束传输按预期工作的光学元件。

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