Acousto-Optic Deflector Multi-Beam Phase Control
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Solution Overview
Problem
Acousto-optic devices face challenges with low diffraction efficiency and nonlinearities, leading to energy loss in undesired diffraction orders and poor control over power levels in multiple output beams, due to generation of harmonic waves and interference between signal frequencies.
Innovation Solution
The use of a drive signal with multiple frequency components, including fundamental and harmonic frequencies, applied to piezoelectric transducers with specific phase offsets to satisfy Bragg conditions and define a Golomb ruler, ensuring efficient splitting of input beams into multiple output beams with controlled intensities and reduced parasitic diffraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a multi-frequency drive signal is applied to an acousto-optic deflector to generate multiple output beams, then the quantity of output beams increases, but intermodulation interference between frequencies increases causing loss of energy in undesired diffraction orders
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating and applying phase offsets to each frequency component in the multi-frequency drive signal. These phase offsets are specifically designed to counteract the intermodulation interference that would otherwise occur between frequency components, thereby preventing energy loss in undesired diffraction orders before the interference can degrade performance
Solution Approach 2:
The patent changes the phase parameter of each frequency component in the drive signal. By adjusting the phase of individual frequency components relative to a common reference frequency, the system optimizes the constructive interference in desired diffraction orders while suppressing parasitic waves, thereby improving diffraction efficiency across all output beams
2Adaptability or versatility
If multiple frequency components are used to create multiple output beams, then beam steering capability improves, but control precision over power levels in each beam deteriorates due to interference
Solution Approach 1:
The patent achieves precise control over power levels by independently adjusting the phase parameter of each frequency component. The phase offset for each frequency is calculated based on its relationship to a common reference frequency, allowing precise control of energy distribution across multiple output beams while maintaining beam steering capability
Solution Approach 2:
The system employs feedback by continuously monitoring the actual power levels in each output beam and adjusting the phase offsets of the corresponding frequency components. This closed-loop control ensures that the desired power distribution is achieved and maintained despite variations in operating conditions
3Power
If high power levels are applied to the acousto-optic deflector to increase output beam intensity, then the power of output beams increases, but intermodulation interference increases causing distortion
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating phase offsets that specifically counteract intermodulation interference effects. These phase adjustments are applied before the high-power signal is driven into the acousto-optic deflector, preventing the generation of parasitic waves and minimizing distortion even at high power levels
Solution Approach 2:
The patent converts the harmful intermodulation interference into a beneficial effect by using the phase offset adjustments to reshape the interference pattern. The phase control transforms what would be destructive parasitic waves into constructive interference that enhances the desired output beams while suppressing unwanted diffraction orders
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 enhances diffraction efficiency, channels energy into desired output beams, and achieves precise control over power distribution among output beams, reducing intensity variations and parasitic waves, thereby improving the performance of acousto-optic devices in generating multiple beams.
Implementation Method 1
A transducer, such as a piezoelectric transducer, is attached to an acousto-optic medium, typically a suitable transparent crystal or glass. The transducer is driven by an electrical signal to vibrate at a certain frequency, and thus creates sound waves in the acousto-optic medium.
Implementation Method 2
The expansion and compression of the acousto-optic medium due to the sound waves modulate the local index of refraction and thus create a grating structure within the medium, with a period determined by the frequency of the drive signal. A beam of light that is incident on this grating will thus be diffracted as it passes through the device.
Implementation Method 3
Acousto-optic deflectors use the diffraction of the incident beam to steer the angle of the output beam. The angle of deflection of the output beam depends on the period of the grating structure in the acousto-optic material and may thus be adjusted by appropriately varying the drive signal frequency.
Implementation Method 4
Acousto-optic deflectors may be driven with a multi-frequency drive signal in order to diffract the incident beam into multiple output beams at different, respective angles. The relative phase of each frequency is also controlled so that a low maximum power is achieved for the combined signal that is presented to the acousto-optic deflector without decreasing the overall average power of the multiple signal frequencies.
Data Source
AI summary
Optical apparatus includes an acousto-optic medium and an array of multiple piezoelectric transducers attached to the acousto-optic medium. A drive circuit is coupled to apply to the piezoelectric transducers respective drive signals including at least first and second frequency components at different, respective first and second frequencies and with different, respective phase offsets for the first and second frequency components at each of the multiple piezoelectric transducers.