Encyclopedia > letter B > beam collimators

Beam Collimators

Author: the photonics expert Dr. Rüdiger Paschotta (RP)

Definition: devices for collimating optical beams

Categories: article belongs to category general optics general optics, article belongs to category laser devices and laser physics laser devices and laser physics

DOI: 10.61835/az7 Cite the article: BibTex plain text HTML Link to this page! LinkedIn

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 focus close to the output aperture, or a mild focus somewhat away from it (see Fig. 1).

Essentially, a beam collimator contain 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 article on fiber collimators
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

collimated beam — Figure 1: Beam radius versus position in a set up 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:

fiber collimation — 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.

More to Learn

Collimated beams Fiber collimators Laser diode collimators Parabolic mirrors Rod lenses

Suppliers

The RP Photonics Buyer's Guide contains 59 suppliers for beam collimators. Among them:

TOPTICA Photonics

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).

Shanghai Optics

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.

PowerPhotonic

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.

Edmund Optics

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.

Avantier

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.

CSRayzer Optical Technology

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

DPM Photonics

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.

Questions and Comments from Users

Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

Please do not enter personal data here. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him, e.g. via e-mail.

By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.