Electrooptic Crystal Beam Deflection via Space-Charge Field
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Solution Overview
Problem
Conventional optical deflection techniques, such as polygon mirrors, galvano mirrors, acousto-optic deflectors, and MEMS, face limitations in speed, size, power consumption, and deflection angle, making them unsuitable for high-speed and high-resolution applications like laser printers and video apparatuses.
Innovation Solution
Employing an electrooptic crystal with a large Pockels or Kerr constant, such as KLTN, and utilizing a parallel-plate or horizontal electrode configuration to generate a space-charge limited electric field, which tilts the refractive index and enhances beam deflection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a polygon mirror is used for beam deflection, then the deflection mechanism is simple, but the rotational speed is limited and cannot achieve high-speed operation
Solution Approach 1:
The patent replaces the mechanical rotation system of polygon mirrors with an electro-optic system. An electro-optic crystal modulates the refractive index through applied voltage, deflecting the laser beam without any moving mechanical parts. This substitution enables response speeds in the GHz range, dramatically exceeding the rotational speed limits of mechanical polygon mirrors.
2Speed
If a galvano mirror with machine winding is used, then rapid operation is achieved, but downsizing is difficult and power consumption is large
Solution Approach 1:
The patent replaces the electromagnetic drive system (coil and magnet) of galvano mirrors with an electro-optic modulation system. The electro-optic crystal responds to voltage changes without requiring large magnetic components, enabling significant size reduction while maintaining rapid response capability in the MHz to GHz range.
Solution Approach 2:
The patent changes the operating parameters by using electro-optic materials with high electro-optic coefficients and applying optimized voltage waveforms. This allows achieving the same deflection speed with much smaller device dimensions compared to conventional galvano mirrors that rely on mechanical inertia and electromagnetic forces.
3Ease of operation
If acousto-optic deflection is used, then optical diffraction is achieved, but power consumption is large and deflection angle is limited
Solution Approach 1:
The patent replaces the acousto-optic diffraction mechanism with direct electro-optic refraction. Instead of using sound waves to modulate the refractive index (which requires high power), the electro-optic crystal directly changes its refractive index through applied voltage, eliminating the need for high-power acoustic drivers while achieving larger deflection angles.
4Volume of moving object
If MEMS electrostatic drive is used, then miniaturization is achieved, but response is limited to several tens of μm
Solution Approach 1:
The patent replaces the electrostatic drive mechanism of MEMS, which moves physical mirror structures, with an electro-optic modulation system. The electro-optic crystal changes its optical properties through voltage without moving mechanical parts, eliminating the response limitations imposed by mechanical inertia and electrostatic actuation distances.
5Ease of operation
If conventional electro-optic crystal with small Pockels constant is used, then beam deflection is achieved, but deflection angle is small
Solution Approach 1:
The patent changes the material parameter by selecting electro-optic crystals with large Pockels or Kerr constants (such as KLTN, BTO, or PZT). These materials exhibit much stronger refractive index changes under applied voltage, producing significantly larger deflection angles while maintaining ease of operation through voltage control.
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 achieves a significantly larger deflection angle and faster response frequency compared to conventional methods, enabling efficient beam deflection and phase modulation while reducing device size and power consumption.
Implementation Method 1
a phenomenon such that, upon the application of a voltage to an electrooptic crystal, the refractive index of the crystal is changed by the electrooptic effect
Implementation Method 2
utilizing a parallel-plate or horizontal electrode configuration to generate a space-charge limited electric field, which tilts the refractive index and enhances beam deflection efficiency
Data Source
Figure 1
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AI summary
An electrooptic device having a simple structure that can efficiently increase deflection of a beam is provided. The device includes: an electrooptic crystal (11) having an electrooptic effect; an electrode pair of a positive electrode (12) and a negative electrode (13) for generating an electric field inside the electrooptic crystal; and a power source for applying a voltage between the electrode pair so as to generate a space charge inside the electrooptic crystal. With this arrangement, by using a simple structure, a change in a deflection angle is temporally rapid, and a large deflection angle that can not be obtained by a conventional electrooptic crystal prism can be acquired at a low applied voltage.