Features

• 30 mm Cage System- and SM1 Lens Tube-Compatible Cubes
• Build 2D and 3D Cage and Lens Tube Systems

The 30 mm cage cubes offered here are ideal for building optical setups involving prisms, beamsplitters, and other optics that cause a 90° deviation of the beam path. They are compatible with the accessories sold below, those featured in the table below, as well as our selection of 30 mm Cage Accessories and Cage Components. The Application Ideas tab shows how to use our cage cubes and accessories to construct a beam combiner with a dichroic mirror as well as a variable attenuation beamsplitter with a polarizing beamsplitting cube.

Thorlabs offers a wide and growing complement of accessories for 30 mm cage cubes, including optic mounts, platforms, rotating platforms, and cover plates. These tools provide a complete family of versatile building blocks suited for virtually any 30 mm cage cube optomechanical setup.

We also offer smaller 1.5" cage cubes that are ideal for mounting prisms and cube-shaped optics, as well as a dichroic cage cube with a built-in FFM1 mount.

30 mm Cage Cubes and Accessories
Cage Cubes	Optic Mounts	Platforms	Rotating Platforms	Cover Plates

Combining Two Beams

Our cage system can be used to build an easily adjustable beam combiner. This setup is based on the use of an appropriate dichroic mirror for the wavelengths that need to be combined. One beam needs to be in the transmission band of the dichroic mirror, while the other needs to be in the reflection band. For this application the reflection band laser is 405 nm and the transmission band laser is 635 nm. The DMLP567 is an appropriate dichroic mirror for the two selected wavelengths.

The dichroic mirror is mounted in a B5C Ø1" optic mount and attached to a B4C kinematic platform. The kinematic platform allows for positioning of the beam that is within the reflection band of the dichroic mirror. This assembly is placed within a C4W cage cube with ER cage rods attached to two adjacent faces. One set of cage rods holds a collimator for the reflection band's fiber coupled laser, while the other set of cage rods holds a collimator for the transmission band's fiber coupled laser.

A more complex setup can be built to combine more than two beams by using multiple dichroic mirrors together.

Variable Attenuation Beamsplitter

In normal operation, the variable beamsplitter/attenuator utilizes a half-wave plate to rotate the polarization of a previously linearly polarized beam of light. At the beamsplitter interface, p-polarized light will be transmitted, while s-polarized light will be reflected. By choosing the correct orientation with the half-wave plate, one can determine the amount of p-polarized and s-polarized light incident upon the interface (as shown in Figure 1 below).

Figure 1. Normal Variable Beamsplitter Operation

The variable attenuation beamsplitter is a common component in many large optical systems and can serve as the basic building block for various applications just as; beam sampling, beam combining, beam splitting, power balance, and reflection isolation. Due to the modular design of the 30 mm cage cube system, this device can be easily integrated into a larger cage cube system. A variable attenuation beamsplitter can function at any wavelength supported by the optics of the system. For this application the optics were chosen for a 670 nm variable beamsplitter.

The polarization beamsplitting cube sits upon a B4CRP precision rotation platform and is held in place with a B6C cage cube clamp. The precision rotation platform allows for precise alignment of the polarization beamsplitting cube relative to the incident laser beam and also yields control over output beam alignment. This assembly is mounted within a C6W 30 mm cage cube with ER cage rods attached to hold a half-wave plate and rotation mount. The rotation mount is a CRM1P which is designed for integration into a 30 mm cage system. The precision control over the rotation is particularly useful when attempting to maximize or minimize a beam throughput. The zero-order mounted half-wave plate threads directly onto this rotation mount.

Click to Enlarge

An example of the standard cage
plate measurements determining
cage system compatibility.

Cage System Overview

The Cage Assembly System provides a convenient way to construct large optomechanical systems with an established line of precision-machined building blocks designed for high flexibility and accurate alignment.

16 mm, 30 mm, and 60 mm Cage System Standards

Thorlabs offers three standards defined by the center-to-center spacing of the cage assembly rods (see image to right). The 16 mm cage, 30 mm cage, and 60 mm cage standards are designed to accomodate Ø1/2", Ø1", and Ø2" optics, respectively. Specialized cage plates that allow smaller optics to be directly inserted into our larger cage systems are also available.

Standard Threads

The flexibility of our Cage Assembly System stems from well-defined mounting and thread standards designed to directly interface with a wide range of specialized products. The three most prevalent thread standards are our SM05 Series (0.535"-40 thread), SM1 Series (1.035"-40 thread), and SM2 Series (2.035"-40 thread), all of which were defined to house the industry's most common optic sizes. Essential building blocks, such as our popular lens tubes, directly interface to these standards.