Diffractive Beam Splitter for Thinner Wavelength Selective Switches

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Solution Overview

Problem

Existing optical wavelength selective switches face challenges in reducing device size due to the thickness of beam splitters, which require precise positioning and high-precision polishing, limiting the miniaturization of optical communication systems.

Innovation Solution

The use of a diffractive beam splitter with a liquid crystal diffractive element and a twisted structure, combined with a retardation plate, to split and collimate light efficiently, allowing for a thinner design that reduces the overall device size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional beam splitter material (MgF2, YVO4, calcite) is used, then the light splitting function is achieved, but the element thickness increases

Engineering Contradiction:

Improvelight splitting functionVSAvoidelement thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent changes the fundamental parameter of the beam splitter material from conventional bulk materials (MgF2, YVO4, calcite) to a liquid crystal diffractive element. This parameter change enables the beam splitter to achieve the same light splitting function with significantly reduced thickness, as liquid crystal diffractive elements can be fabricated as thin films while maintaining optical functionality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/optical system based on bulk material refraction and birefringence with a diffractive optical system. The liquid crystal diffractive element uses diffraction principles to split light into multiple beams, substituting the conventional mechanism that relies on thick material layers for total internal reflection and polarization separation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a conventional beam splitter is used, then light splitting is achieved, but position adjustment space is required which increases device size

Engineering Contradiction:

Improvelight splitting functionVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent changes the operational parameters of the beam splitter by using a liquid crystal diffractive element that can be precisely positioned and controlled. The thin-film nature of liquid crystal elements allows for reduced positioning tolerances and smaller adjustment spaces compared to thick conventional beam splitters, thereby reducing the overall device volume.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If high-precision polishing is applied to conventional beam splitter surfaces, then surface smoothness is improved, but the manufacturing process becomes complicated

Engineering Contradiction:

Improvesurface smoothnessVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical polishing process with a photolithographic fabrication process for creating the liquid crystal diffractive element. Instead of mechanically polishing thick material surfaces to achieve the required smoothness, the diffractive structure is directly patterned using standard semiconductor manufacturing techniques, which inherently provide the necessary surface precision without complex polishing steps.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the manufacturing approach from subtractive (polishing) to additive/pattern-based (photolithography). The liquid crystal diffractive element is fabricated with precise surface characteristics through deposition and patterning processes, eliminating the need for high-precision mechanical polishing that complicates the manufacturing of conventional beam splitters.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The proposed solution enables a compact optical wavelength selective switch system by thinning the beam splitter, facilitating a reduction in the overall device size while maintaining effective light splitting and collimation capabilities.

Implementation Method 1

the light splitting element is a diffractive element

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

the liquid crystal diffractive element has a twisted structure of liquid crystals

Methodology Applied

Scientific EffectLiquid crystal twisting: Liquid Crystals

Implementation Method 3

The polarization state of one beam is rotated by a retardation plate to obtain linearly polarized light components whose polarization directions are parallel to each other

Methodology Applied

Scientific EffectRetardation: Birefringence

Implementation Method 4

a light collimating member for collimating the split light components

Methodology Applied

Scientific EffectCollimation: Lens

Data Source

PatentUS20260036820A1Beam splitter and optical wavelength selective switch system

Publication Date: 2026.02.05 FUJIFILM CORP

AI summary

Provided are a thin beam splitter and an optical wavelength selective switch system including the beam splitter. The beam splitter includes: a light splitting element that splits incident light in two directions; and a light collimating member for collimating the split light components, in which the light splitting element is a diffractive element, and a splitting angle of the light splitting element is 20° or more.