Optical Modulator Shielding for Low-Frequency Detection
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Solution Overview
Problem
Compound semiconductor single crystals, such as ZnTe and GaAs, fail to accurately detect low-frequency electromagnetic waves due to carrier migration negating the electric field, leading to insufficient electro-optic effects, and external light further complicates this by generating carriers that interfere with electric field detection.
Innovation Solution
An optical modulator is designed with incidence limiting means, such as dichroic mirrors or pinhole shielding, and a low-permittivity light-blocking shielding member to restrict external light and reduce carrier generation, ensuring the electro-optic crystal can effectively modulate low-frequency electromagnetic waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a compound semiconductor single crystal is used as an electro-optic crystal, then high-frequency electromagnetic waves (exceeding 1 THz) can be detected, but low-frequency electromagnetic waves (10 kHz or less) cannot be accurately detected due to carrier migration negating the electric field
Solution Approach 1:
The patent changes the electrical parameters of the electro-optic crystal by adding donor impurities (such as In, Ga, or Ge) to reduce carrier concentration and increase resistance. This parameter change suppresses carrier migration at low frequencies, allowing the electro-optic effect to remain stable and enabling accurate detection of low-frequency electromagnetic waves while maintaining high-frequency detection capability
Solution Approach 2:
The patent applies preliminary anti-action by pre-compensating for the harmful carrier migration effect through controlled addition of donor impurities. This creates a balanced carrier concentration that prevents the electric field from being negated during low-frequency operation, thereby maintaining detection reliability across both low and high frequency ranges
2Measurement precision
If donor impurities are added to reduce carrier concentration, then electro-optic effect is improved at low frequency, but outside light entering the crystal generates carriers that negate the electric field
Solution Approach 1:
The patent extracts or removes the harmful outside light from reaching the electro-optic crystal by implementing a shielding structure. This eliminates the source of unwanted carrier generation while preserving the beneficial low-frequency electro-optic effect achieved through donor impurity addition
Solution Approach 2:
The patent introduces a shielding member as an intermediary element between the outside environment and the electro-optic crystal. This mediator blocks harmful light while allowing the desired electromagnetic waves to interact with the crystal, thus protecting the carefully balanced carrier concentration from disruption
3Reliability
If the electro-optic crystal is exposed to outside light, then carriers are generated that migrate and negate the electric field, but complete isolation may affect operational flexibility
Solution Approach 1:
The patent applies local quality by implementing shielding only where necessary - specifically protecting the electro-optic crystal from outside light while maintaining operational accessibility. The shielding is localized to the crystal region rather than the entire device, preserving usage flexibility in non-critical areas while ensuring detection stability where required
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 configuration significantly reduces external light entering the crystal, preventing carrier generation and enhancing the detection sensitivity of low-frequency electric fields, allowing reliable detection of low-frequency electromagnetic waves.
Implementation Method 1
an optical modulator using a compound semiconductor single crystal which generates an electro-optic effect
Implementation Method 2
a shielding member which is formed from a low-permittivity material having a light blocking effect
Implementation Method 3
the incidence limiting means may be a dichroic mirror, which is configured to permit the passage of only light of the same wavelength as the laser beam
Data Source
AI summary
In an optical modulator capable of modulating incident laser beam L by a compound semiconductor single crystal having a property of generating an electro-optic effect, the attenuation of the signal strength in a low frequency band is prevented without lowering the carrier concentration of the compound semiconductor.The optical modulator 23 comprises: incidence limiting means 25 which is provided on or near an incidence plane 24a, on which the laser beam L can be incident, of the compound semiconductor single crystal 24 so as to limit incidence of light other than the laser beam L on the incidence plane 24a; and a shielding member 26 which is formed from a low-permittivity material having a light blocking effect, and covers a surface 24c of the compound semiconductor single crystal 24 extending along a traveling direction of the laser beam L that entered the compound semiconductor single crystal 24.