Optical Modulator Flexural Vibration Laser Frequency Shifting
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Solution Overview
Problem
Existing laser Doppler measurement devices face challenges in efficiently shifting the frequency of laser light due to the limitations of quartz crystal AT vibrators, leading to increased costs from high-frequency modulation signals that require complex processing circuits.
Innovation Solution
An optical modulator employing a vibrator with flexural vibration and a diffraction grating arranged in parallel to the vibration direction, allowing for efficient frequency shifting of laser light with lower resonance frequencies, reducing the complexity and cost of processing circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a quartz crystal AT vibrator with thickness-shear vibration is used, then the frequency of laser light can be shifted, but the resonance frequency is high which increases the complexity and cost of processing circuits
Solution Approach 1:
The invention changes the vibration mode parameter from thickness-shear vibration to flexural vibration, which fundamentally alters the resonance frequency characteristics. This parameter change enables the use of lower frequency vibrations while maintaining the frequency shifting capability, thereby simplifying the processing circuit requirements
Solution Approach 2:
Instead of using the conventional thickness-shear vibration mode that produces high frequency, the invention inverts the approach by utilizing flexural vibration mode. This inversion of the vibration mechanism achieves the same frequency shifting function but at lower frequencies, reducing circuit complexity
2Device complexity
If only a quartz crystal AT vibrator is used, then the structure is simple, but the inner product of wave number difference and vibration vector is substantially zero making frequency shifting inefficient
Solution Approach 1:
The invention introduces a diffraction grating as an intermediary element between the laser light and the vibrator. This mediator converts the vibration direction to be substantially perpendicular to the incident laser light, enabling efficient frequency shifting while maintaining structural simplicity
Solution Approach 2:
The invention adds a spatial dimension by introducing a diffraction grating with grooves arranged in a specific direction. This dimensional addition transforms the vibration vector orientation, creating a non-zero inner product with the wave number difference vector and enabling effective frequency shifting
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 solution enables a cost-effective laser interferometer with improved measurement accuracy and resistance to disturbances by utilizing in-plane flexural vibration, achieving higher phase shifts and signal-to-noise ratios.
Implementation Method 1
a diffraction grating disposed in the vibration unit and having a plurality of grooves arranged in parallel along the first direction. A frequency of laser light incident on the diffraction grating is shifted.
Implementation Method 2
a laser Doppler measurement device that grasps a movement of a moving object... a shift amount of a frequency of the laser light is obtained by using heterodyne interference
Implementation Method 3
a vibrator including a vibration unit configured to perform flexural vibration along a first direction
Implementation Method 4
a photodetector configured to receive the laser light including a sample signal derived from an object and the modulation signal, and to output a light reception signal
Data Source
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AI summary
An optical modulator includes: a vibrator configured to perform flexural vibration along a first direction; and a diffraction grating disposed in the vibrator and having a plurality of grooves arranged in parallel along the first direction. A frequency of laser light incident on the diffraction grating is shifted. In addition, it is preferable that the vibrator includes a base portion, a first vibration arm and a second vibration arm disposed side by side along the first direction and coupled to the base portion, the first vibration arm and the second vibration arm perform the flexural vibration along the first direction, and the diffraction grating is disposed on at least one of the first vibration arm and the second vibration arm.