Optical Amplifier Inspection for High-Frequency Jitter Detection
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Solution Overview
Problem
Existing inspection apparatuses struggle to accurately detect minute phenomena, particularly jitter of about 10 ps, in high frequency bands due to limitations in photodetectors with multiplication layers, which are unsuitable for high-speed signal detection.
Innovation Solution
The apparatus includes an optical amplifier separate from the photodetector, amplifying input light without saturation, using a photodetector without a multiplication layer, and ensuring a linear output to enhance detection accuracy in high frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photodetector with a multiplication layer is used to amplify returned light, then detection accuracy is improved, but the device capacity increases making it unsuitable for high frequency band measurement
Solution Approach 1:
An optical amplifier is introduced as an intermediary component between the semiconductor device and the photodetector. The optical amplifier amplifies the returned light before it reaches the photodetector, allowing the use of a simple photodetector without multiplication layers while maintaining high detection accuracy. This mediator resolves the contradiction by providing signal amplification without increasing photodetector complexity.
2Reliability
If the light amount irradiated to the semiconductor device is reduced to prevent destruction, then device safety is improved, but detection accuracy deteriorates due to reduced returned light amount and increased noise influence
Solution Approach 1:
The optical amplifier performs preliminary amplification of the returned light signal before it reaches the photodetector. By amplifying the weak signal in advance, the system can use reduced light irradiation amounts for device safety while maintaining sufficient signal strength for accurate detection, thus resolving the contradiction between device safety and detection accuracy.
3Power
If saturation occurs in the optical amplifier, then amplification gain increases, but minute signals disappear and detection accuracy deteriorates
Solution Approach 1:
The optical amplifier operates in a partial amplification mode where it provides sufficient gain to amplify weak returned light signals detectably without reaching saturation. This partial action approach maintains the ability to detect minute signals while avoiding the distortion that would occur at full saturation, resolving the contradiction between amplification gain and detection accuracy.
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
Enables accurate detection of phenomena in a wide band, including high frequency bands up to 20 GHz, by preventing signal loss and maintaining detection accuracy through linear amplification and noise dominance.
Implementation Method 1
an optical amplifier configured to amplify input light and output the amplified light
Implementation Method 2
a photodetector configured to detect the light output from the optical amplifier
Data Source
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AI summary
An inspection apparatus includes a light source that emits light, an optical amplifier that amplifies input light and outputs the amplified light, an optical system (an objective lens, an imaging optical system, and a scanning optical system) that irradiates a semiconductor device with the light from the light source and guides light from the semiconductor device to the optical amplifier, and a photodetector that detects the light output from the optical amplifier, and the optical amplifier amplifies the input light so that saturation does not occur.