In optical systems, controlling not only the intensity of light but also its polarization state is essential for achieving high-precision optical performance.

Wave plates are widely used in laser optics, microscopy, optical communications, medical and industrial illumination systems, projectors, and astronomical observation. However, conventional wave plates generally have a wavelength-dependent retardance, making it difficult to maintain the desired polarization state over a wide wavelength range.

Luceo’s SB-RETAX (Super Broadband Wave Plate) was developed to address this challenge.

The 5-layer type of SB-RETAX covers an exceptionally wide wavelength range of 450 to 1100 nm, from visible light to near-infrared light, with a single wave plate.

In this article, we explain the technology behind SB-RETAX and the advantages it can provide for optical system design.

1. What Is a Wave Plate?

A wave plate is an optical component used to control the polarization state of light.

By introducing a specific amount of retardance (phase difference) between the orthogonal polarization components of light, a wave plate can change the polarization state.

Typical examples include:

Half-wave plate (λ/2): Rotates the polarization direction of linearly polarized light.
Quarter-wave plate (λ/4): Converts linearly polarized light into circularly polarized light, and vice versa.

For example, combining a quarter-wave plate with a polarizer can generate circularly polarized light. This configuration can also be used to create an optical isolator function that suppresses reflected light returning into an optical system.

2. The Challenge of Wavelength Dependence in Conventional Wave Plates

Conventional wave plates are generally designed to provide a specific retardance at a particular wavelength.

For example, a quarter-wave plate optimized for 550 nm may provide the desired quarter-wave retardance at 550 nm. However, when light at 450 nm or 650 nm passes through the same wave plate, the retardance can deviate from the target value.

As a result, the polarization state also changes depending on the wavelength.

This becomes a significant limitation in optical systems that use multiple wavelengths.

When different wavelengths need to be controlled independently, conventional optical designs may require multiple wave plates or a mechanism for switching between them.

This can increase the number of optical components and make the optical system more complicated.

3. SB-RETAX: One Wave Plate for a Wide Wavelength Range

Luceo developed SB-RETAX to overcome the wavelength dependence of conventional wave plates.

The key feature of SB-RETAX is its ability to provide a nearly constant retardance over a wide wavelength range with a single wave plate.

For example, the SB-RETAX-5L-1/4λ is designed to provide approximately 1/4-wave retardance over the wavelength range from 450 to 1100 nm.

This means that visible and near-infrared light can be controlled using a single optical component.

By eliminating the need to switch between wave plates for different wavelengths, SB-RETAX can provide greater flexibility in optical system design.

4. The Key Technology: Multilayer Lamination of Birefringent Resin Films

How can SB-RETAX maintain nearly constant retardance over such a wide wavelength range?

The key is Luceo’s multilayer technology using birefringent resin films.

Multiple birefringent films with carefully designed optical characteristics are laminated together and bonded between optical glass substrates.

Optically designed multilayer structure

Rather than relying on the optical characteristics of a single material, SB-RETAX uses multiple birefringent films with different optical characteristics.

Each layer contributes to the overall polarization control, and the optical design is optimized so that the combined structure provides the desired retardance over a broad wavelength range.

In other words, the technology is not simply based on using a “wideband material.”

Instead, Luceo combines multiple optical films with different characteristics and designs the multilayer structure so that the entire wave plate achieves the desired polarization performance.

This combination of optical design, film technology, and precision lamination technology is one of the key advantages of SB-RETAX.

5. Three-Layer and Five-Layer Configurations

SB-RETAX is available in different configurations depending on the required wavelength range.

3-Layer Type

The 3-layer type is designed for a wavelength bandwidth of approximately 300 nm.

Examples include:

450–700 nm
500–800 nm
600–900 nm
800–1100 nm
5-Layer Type

The 5-layer type provides an exceptionally broad wavelength range:

450–1100 nm

This range covers both visible light and near-infrared light with a single wave plate.

Rather than simply selecting the widest possible wavelength range, the appropriate configuration can be selected according to the light source and optical system requirements.

6. Wide Bandwidth and High Retardance Accuracy

For precision optical applications, wavelength coverage is not the only important factor.

The accuracy of the retardance is also critical.

For the SB-RETAX 5-layer type, the retardance tolerance is specified as:

λ/50 for 450–550 nm
λ/80 for 550–1100 nm

This combination of wide wavelength coverage and high retardance accuracy makes SB-RETAX suitable for demanding research and industrial optical applications.

7. Five Advantages of Using One Wave Plate

Using SB-RETAX in an optical system can provide several design advantages.

1. Reduction of optical components

Multiple wave plates for different wavelengths may be replaced by a single SB-RETAX wave plate.

This can help minimize the number of optical components.

2. Elimination of wavelength-switching mechanisms

If a conventional system requires wave plates to be switched according to wavelength, mechanical mechanisms may be necessary.

SB-RETAX can reduce the need for such switching mechanisms, contributing to a simpler optical system.

3. Potential for smaller and lighter equipment

Reducing the number of optical components and switching mechanisms can help create more compact and lightweight equipment.

4. Simplified optical-axis adjustment

When several wave plates are used, each optical component must be precisely aligned.

Using a single broadband wave plate can reduce the complexity of optical-axis alignment.

5. Easier integration into multi-wavelength systems

SB-RETAX is particularly useful for systems that use multiple wavelengths or broadband light sources.

A single optical component can provide polarization control across a broad wavelength range.

8. Large-Aperture Designs and Customization

Another advantage of SB-RETAX is the flexibility provided by its resin-film-based structure.

Because birefringent resin films are used as the optical functional material, SB-RETAX can be manufactured in sizes larger than conventional crystal wave plates.

Standard products are available in diameters such as:

φ20 mm
φ25 mm
φ30 mm

Larger sizes and various shapes can also be considered as customized products depending on the application.

SB-RETAX is also available in both 1/4-wave and 1/2-wave configurations, depending on the required polarization control.

Furthermore, combining SB-RETAX-1/4λ with a broadband polarizer can create a broadband circular polarizer for applications requiring circular polarization over a wide wavelength range.

9. Applications of SB-RETAX

SB-RETAX can be considered for a wide range of optical applications where multiple wavelengths or broadband light sources are used.

Laser Optics

A single broadband wave plate can be used for polarization control in systems using multiple laser wavelengths.

Microscopy and Imaging

SB-RETAX can be used for polarization observation and precision optical measurement.

Optical Communications

Broadband polarization control can be useful in optical systems operating across different wavelength bands.

Medical and Industrial Illumination

A single wave plate can simplify the optical configuration of multi-wavelength illumination systems.

Projectors and Displays

Broadband polarization control can contribute to optical systems that handle a wide range of visible wavelengths.

Astronomy and Space Observation

The ability to control polarization from visible wavelengths through near-infrared wavelengths can be useful in advanced observation systems.

10. Conclusion: From “One Wave Plate per Wavelength” to “One Wave Plate for Multiple Wavelengths”

SB-RETAX offers a different approach to broadband polarization control.

Its key advantages can be summarized as follows:

450–1100 nm coverage with a single wave plate
High retardance accuracy across a wide wavelength range
Multilayer optical design using birefringent resin films
Potential for larger apertures and customized sizes and shapes
Simplification of multi-wavelength optical systems

Instead of preparing a separate wave plate for each wavelength or using a mechanism to switch between multiple wave plates, SB-RETAX enables a single optical component to control polarization across a broad wavelength range.

This can contribute to optical systems that are simpler, more compact, and easier to integrate, while maintaining precise polarization control.

Luceo has developed its polarization-related technologies through many years of experience in optical films, lamination, and optical component manufacturing.

We can also discuss customized specifications according to your optical system, including wavelength range, size, shape, substrate material, thickness, and retardance.

If you are considering a multi-wavelength optical system or need a wave plate covering both visible and near-infrared wavelengths, please contact Luceo for technical consultation.

Learn more about SB-RETAX and our Super Broadband Wave Plate solutions.