Injection-Locked Laser Diode Amplifier Stabilization for Low-Noise Power
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Solution Overview
Problem
Existing systems for ultra-high precision interferometric measurements, such as multiple axes distance metrology in lithography, face challenges with low phase noise laser sources and shot noise limited detection, often requiring higher output power lasers which can increase system cost and complexity.
Innovation Solution
A system comprising a laser diode, an interferometer, and a controller that stabilizes the output of the laser diode by adjusting the driving current and maintaining the laser diode in an injection-locked regime, using an active feedback mechanism to ensure stable and low noise optical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple lasers are used to increase output power, then the output power level is improved, but the system cost and complexity increase
Solution Approach 1:
The patent combines a laser diode amplifier with an injection-locked laser to create a hybrid system. The injection-locked laser provides stable frequency and low phase noise, while the laser diode amplifier boosts the output power. This merging of two different laser technologies resolves the contradiction by achieving high power output without requiring multiple separate laser systems.
Solution Approach 2:
The patent introduces an optical amplifier as an intermediary component between the injection-locked laser and the final output. This amplifier takes the low-power, stable-frequency light from the injection-locked laser and amplifies it to the required power level, thereby achieving high output power without the complexity of multiple lasers.
2Power
If multiple lasers are used to increase output power, then the output power level is improved, but the reliability of the system deteriorates
Solution Approach 1:
By merging the frequency stability of the injection-locked laser with the power amplification capability of the laser diode amplifier, the system achieves high output power while maintaining reliability. The injection-locked laser acts as a stable reference that reduces phase noise, and the amplifier simply boosts power without introducing additional frequency instability.
3Measurement precision
If higher output power lasers are used to meet shot noise limit, then the shot noise limit is improved, but the system cost increases
Solution Approach 1:
The optical amplifier serves as an intermediary that takes the low-power output of the injection-locked laser and amplifies it to the required level for meeting shot noise limits. This approach is more cost-effective than purchasing and integrating multiple high-power lasers, as the amplifier is a simpler, more economical component.
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 system achieves stable and low noise optical signals with increased power, maintaining the laser diode in the injection-locked regime while reducing system complexity and cost compared to using multiple lasers.
Implementation Method 1
a laser diode adapted to output an optical signal
Implementation Method 2
an interferometer adapted to receive a portion of the optical signal from the laser diode
Data Source
AI summary
A system includes a laser diode adapted to output an optical signal having a wavelength; an interferometer adapted to receive a portion of the optical signal from the laser diode; and a controller comprising a processor and coupled to the laser diode and the interferometer. The controller is connected to a memory that stores instructions, which when executed by the processor cause the processor to: receive the optical signal from the interferometer; determine a first amplitude peak of the optical signal received from the interferometer; compare the first amplitude peak to a previous amplitude peak; increase an driving current to the laser diode; determine a second amplitude peak of the optical signal received from the interferometer; compare the second amplitude peak to the first amplitude peak; and based on the comparison of the second amplitude peak to the first amplitude peak, increase or decrease the driving current to the laser diode so the optical signal received from the interferometer is maintained in a desired wavelength.