Gain Chip Characterization via Tunable Probe Laser
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Solution Overview
Problem
Existing methods cannot effectively measure the gain profile of a gain chip as a function of wavelength without integrating it into an external cavity laser, limiting the characterization and prediction of tunable laser behavior.
Innovation Solution
A system and method utilizing a tunable quantum cascade laser as a probe light source to vary wavelengths and measure light intensity with and without the gain chip powered, focusing light through a transparent face of the gain chip, and positioning the light to scan across the chip to determine the gain profile, including the use of a reflectivity standard and polarization alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain chip is integrated into an external cavity laser to measure gain profile, then the measurement can be performed, but the device complexity and measurement procedure become cumbersome
Solution Approach 1:
The patent extracts the gain chip from the external cavity laser system and characterizes it as a standalone component. By removing the gain chip from the complex laser assembly, the measurement process is simplified while still enabling gain profile characterization through direct optical coupling to the waveguide facet.
Solution Approach 2:
The measurement system is segmented into separate functional components: a probe laser source, optical coupling elements, and a detector. This segmentation allows the gain chip to be characterized independently without requiring the entire external cavity laser assembly, reducing device complexity.
2Device complexity
If the gain chip is characterized without integration into external cavity laser, then the device complexity is reduced, but the ability to measure gain profile as function of wavelength is limited
Solution Approach 1:
The patent employs a universal optical coupling approach that can characterize the gain chip independently while still providing wavelength-dependent gain profile measurements. The probe laser can be tuned across wavelengths and coupled to the waveguide, enabling comprehensive characterization without permanent integration into a specific laser configuration.
Solution Approach 2:
The patent changes the operational parameters by using a tunable probe laser to sweep through different wavelengths and measuring the optical response at each wavelength. This parameter variation enables the construction of a complete gain profile as a function of wavelength, achieving measurement precision comparable to integrated methods.
3Measurement precision
If light is focused into the waveguide to characterize gain chip, then the measurement accuracy is improved, but the alignment precision required increases
Solution Approach 1:
The patent introduces intermediary optical elements (lenses, coupling optics) between the probe laser and the waveguide facet. These intermediaries facilitate precise light coupling by focusing and directing the probe beam onto the waveguide, improving measurement accuracy while managing the alignment requirements through optical design rather than direct mechanical precision.
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 characterization of gain chips to simulate their behavior in external cavity lasers, predicting tunable laser performance across a range of wavelengths without the need for integration, improving the understanding and optimization of gain chip performance.
Implementation Method 1
an optical system that focuses the output light signal into the waveguide through the transparent face
Implementation Method 2
a waveguide having a reflective face on a first surface of the gain chip
Data Source
AI summary
A system adapted for characterizing gain chips and a method for characterizing gain chips are disclosed. The system includes a probe light source that generates an output light signal characterized by a wavelength that can be varied in response to a wavelength control signal and a mounting stage adapted for receiving a gain chip characterized by a waveguide having a reflective face on a first surface of the gain chip and a transparent face on a second surface of the gain chip. The system also includes an optical system that focuses the output light signal into the waveguide through the transparent face; and a controller that causes the probe light source to generate the output light signal and measures an intensity of light both with and without the gain chip being powered for each of a plurality of different wavelengths to form a gain profile for the gain chip.