beam collimators (original) (raw)

Definition: devices for collimating optical beams

Categories: general optics, laser devices and laser physics

• optical elements
  • achromatic optics
  • adaptive optics
  • aspheric optics
  • custom optics
  • diffractive optics
  • fiber optics
  • flat optics
  • large diameter optics
  • laser optics
  • nonlinear optics
  • optical elements for imaging
  • polarization optics
  • refractive optical elements
  • reflective optical elements
  • beam splitters
  • beam collimators
  • beam expanders
  • beam homogenizers
  • diffusers
  • group velocity delay compensation plates
  • optical apertures
  • optical attenuators
  • optical filters
  • optical modulators
  • optical windows
  • phase corrector plates
  • (more topics)

Related: collimated beamsfiber collimatorsfiber lenseslaser diode collimatorsparabolic mirrorsrod lensesball lenses

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📦 For purchasing beam collimators, use the RP Photonics Buyer's Guide — an expert-curated directory for finding all relevant suppliers, which also offers advanced purchasing assistance.

Contents

What are Beam Collimators?

The purpose of a beam collimator is essentially to transform a strongly diverging light beam into a collimated beam, i.e., a beam where light propagates essentially only in one direction, and the beam divergence is weak. The output beam may have its beam waist close to the output aperture, or a mild focus somewhat away from it (see Fig. 1).

Essentially, a beam collimator contains some kind of focusing lens, or sometimes a curved mirror, and usually some opto-mechanics for stable mounting and possibly adjustment.

Typically, beam collimators are applied in conjunction with the following types of light sources:

• optical fibers — see the articles on fiber collimators and fiber lenses
• laser diodes of different kinds, e.g. single-mode emitters, broad-area laser diodes and devices such as diode bars (diode arrays) with multiple emitters — see the article on laser diode collimators
• other waveguide devices, for example in integrated optics
• free-space laser sources, e.g. diode-pumped solid-state lasers

Figure 1: Beam radius versus position in a setup where a tightly focused beam is collimated with a lens, generating a mild focus somewhat behind it.

In many cases, the collimation is done in both directions perpendicular to the beam, but there are also beam collimators working in one direction only — for example, fast axis collimators made as rod lenses, which are attached to certain laser diodes.

Typical Requirements

The requirements on a beam collimator can be very different, depending on the light source with which it is used:

Figure 2: Fiber collimator with an aspheric doublet lens, not including the mechanical mount.

• Some light sources exhibit a strong beam divergence, and it is then often necessary to use aspheric optics to avoid significant beam quality deterioration due to spherical aberrations.
• In some cases, the beam is strongly asymmetric, with much stronger divergence in one direction than the other. A simple beam collimator may then produce an elliptical beam, but one may apply additional elements such as an anamorphic prism pair for obtaining a circular beam profile.
• While some collimators can be used with a fixed alignment, others need to be adjustable, at least concerning the focus, which can be modified through the distance between light source and collimation lens.
• The beam pointing stability of the generated beam depends on how mechanically stable the setup is. Note that tiny thermal drifts, for example, may cause significant changes in beam direction particularly in cases where the focal length of the collimating lens is small.
• Some devices need to work with very high optical powers, so that one needs to minimize propagation losses and avoid thermal effects. For the highest power levels, purely reflective telescopes (i.e., with curved mirrors instead of lenses) must be used.

Frequently Asked Questions

What is the purpose of a beam collimator?

A beam collimator is an optical device used to transform a diverging light beam into a collimated beam, having a low beam divergence.

Which light sources typically need a beam collimator?

Beam collimators are commonly used with sources that have a high output divergence, such as optical fibers, various types of laser diodes, and other waveguide devices from integrated optics.

When are aspheric lenses used in beam collimators?

Aspheric lenses are used in collimators for light sources with a strong beam divergence. This is to avoid significant degradation of the beam quality which would be caused by spherical aberrations of a simple spherical lens.

How can one circularize the elliptical beam from a laser diode?

After collimating the output of a laser diode, which often results in an elliptical beam, one can use additional elements like an anamorphic prism pair to create a circular beam profile.

Suppliers

Sponsored content: The RP Photonics Buyer's Guide contains 63 suppliers for beam collimators. Among them:

⚙ hardware

The Model 02-M010 is a three-element, air-spaced anastigmat designed specifically for collimating the output of large diameter silica fibers used in high power medical and industrial applications. It is equally suitable for collimating the output of Large Mode Area (LMA) or Photonic Crystal (PC) fibers with smaller numerical apertures. The mechanical assembly allows a precise translation of the lens (without rotation) relative to the fiber face.

The unique design of the Model 02-M010 prevents retroreflections near the fiber face or within the core material. All elements are fused silica (the exception being the 1800–2000 nm collimator optics that are Infrasil) with either V-type or broadband coatings, depending on the operating wavelength range. When used for imaging purposes, the three-element design ensures the output mode from the fiber is preserved, without distortion, even at high throughput powers.

⚙ hardware

Shanghai Optics provide many different types of standard collimating lenses, including aspheric and achromatic lenses for many different light sources such as highly divergent laser diodes. Our standard collimating lenses can convert divergent laser beams to well-collimated laser beams that enter beam expanders for interferometry, laser material processing and laser scanning applications.

We also provide custom collimating lenses for projecting a source at infinity for infinite conjugate testing of optical systems. The collimating lenses can consist of several optical elements. The selection of optical materials and optical configuration depends on the entrance pupil diameter, wavelength, focal length, and field of view of the optical system under test.

⚙ hardware

CSRayzer provides different kinds of sing mode or polarization-maintaining fiber pigtail collimators, large beam collimators, and fixed focus collimators.

⚙ hardware

Avantier offers a wide range of standard collimating lenses, which includes aspheric and achromatic lenses suitable for various light sources such as laser diodes with high divergence. These standard collimating lenses have the ability to convert divergent laser beams into well-collimated laser beams. These collimated beams can then be utilized for laser material processing, laser scanning applications, and interferometry by entering beam expanders.

⚙ hardware

Collimation of single mode fibres can be made simple with the use of a PowerPhotonic fiber collimating micro lens array. We design and manufacture standard and custom in 1D and 2D arrays. All products are made in high grade fused silica and capable of both high efficiency and high power handling and our unique process minimises channel cross talk due to extremely low scatter. Lenses can spheric, aspheric or freeform due to our unique manufacturing process.

⚙ hardware

Edmund Optics offers a wide range of laser accessories, including different kinds of beam collimators and expanders. In particular, we have fiber-coupled collimators which are suitable for FC/PC, FC/APC and SMA connectors. They are easy to integrate and are designed to collimate light exiting a fiber to a desired beam diameter or spot size or to focus light into a fiber when used in reverse.

⚙ hardware

The FiberOut fiber collimator transforms the divergent beam emitted at the end of an optical fiber into a collimated one. It can be equipped with a variety of lenses, matching different fiber mode-field diameters and output beam sizes. The rugged, inexpensive collimator can be used for both FC/PC and FC/APC-type connectors. It can be easily mounted on post or into optical mounts (25 mm diameter).

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