Interferometer Beam Guidance via Prism Deflection
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Solution Overview
Problem
Existing interferometer designs face challenges in implementing simple and efficient quadrature detection, particularly in monolithic structures, due to difficulties in aligning light sources and increased space requirements, as they often rely on λ/4 plates that complicate the optical path length difference measurement between s- and p-polarized light.
Innovation Solution
Incorporating prisms in the reference interferometer's beam path, either upstream or downstream of the beam splitter, to create a phase shift between x- and y-polarized or perpendicular and parallel polarized light through total internal reflection, allowing for precise and space-saving alignment of light sources and detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a λ/4 plate is inserted into the interferometer arm to achieve optical path length difference, then quadrature detection is enabled, but the device complexity and alignment difficulty increase
Solution Approach 1:
The patent removes the λ/4 plate from the interferometer arm and replaces it with a beam splitter configured at specific angles. This extraction of the problematic element simplifies the optical path while maintaining the quadrature detection capability through the beam splitter's inherent optical path length difference creation.
Solution Approach 2:
The beam splitter serves multiple functions: it splits the laser beam into reference and measurement beams, creates the optical path length difference through its angled configuration, and enables quadrature detection without requiring additional retardation elements. This multi-functionality reduces device complexity.
2Measurement precision
If light sources are aligned in the plane defined by optical axes, then measurement precision is improved, but the space requirement and alignment effort increase
Solution Approach 1:
The patent utilizes the angular dimension of the beam splitter to create the optical path length difference. By configuring the beam splitter at specific angles rather than relying on spatial separation in the plane of optical axes, the system achieves precise measurement with reduced setup space.
3Reliability
If the beam is directed onto upper and lower surfaces of the beam splitter, then total internal reflection occurs, but the light source orientation becomes tilted and alignment difficulty increases
Solution Approach 1:
The patent changes the geometric parameters of the beam splitter configuration, specifically the angles at which the beam is directed onto the upper and lower surfaces. This optimization allows total internal reflection to occur while maintaining easier alignment by adjusting the incidence angles to favorable values.
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
This approach results in a compact, robust, and cost-efficient reference interferometer that enables precise measurement of optical path length changes without the need for λ/4 plates, facilitating easier alignment and reduced space requirements while maintaining high precision and accuracy.
Implementation Method 1
Total internal reflection occurs at an interface between the hafnium dioxide layer and the air, which is accompanied by a specific phase shift between perpendicularly and parallel polarized (s- and p-polarized) light.
Implementation Method 2
the phase shift between the s- and p-polarized components of the reference beam is not achieved by a λ/4 plate, but by deflecting the beam onto an upper or lower surface of the reference interferometer coated with HfO2
Data Source
Figure 1a~1b
Figure 2
Figure 3~4
AI summary
The invention relates to a reference interferometer (1) for determining an optical path length change, more particularly a relative optical path length change in interferometer arms (2), comprising a beam splitter (3) and a laser light source (4), wherein the beam splitter (3) is embodied in such a way that a light beam (5) of the laser light source (4) is guidable by means of total-internal reflection over a first side face, in particular an upper side (61), and a second side, in particular a lower side (62), of the beam splitter (3), characterized in that a prism (16') is disposed upstream of the beam splitter (3) in the beam path, said prism allowing the light beam (5) entering into the beam splitter (1) to be deflected, and/or characterized in that a prism (16") is disposed downstream of the beam splitter (3) in the beam path, said prism allowing the light beam (5') emerging from the beam splitter (3) to be deflected. Moreover, the invention relates to an interferometer, a spectrometer and a method for determining an optical wavelength change on the basis of the reference interferometer according to the invention.