Widely Tunable Laser Wavelength Calibration Using a Solid-State Etalon
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Solution Overview
Problem
Existing widely tunable lasers require external instruments for wavelength calibration, which is prone to mechanical instabilities and drifts, and lack cost-effective, maintenance-free methods for absolute wavelength control.
Innovation Solution
An all-solid state device using a solid-state etalon with a distinct wavelength-specific transmission/reflection function and a wavelength shift tracking device, such as a non-balanced interferometer, allows for absolute wavelength determination and tracking during a wavelength sweep, eliminating the need for external instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external instruments such as spectrometers or spectral analyzers are used for wavelength calibration, then absolute wavelength control is achieved, but the system becomes complex, costly, and prone to mechanical instabilities and drifts
Solution Approach 1:
The patent extracts the wavelength calibration function from external instruments and implements it using an integrated solid-state etalon within the laser system itself. The etalon provides wavelength-specific transmission/reflection characteristics that enable self-calibration, eliminating the need for external spectrometers or spectral analyzers and reducing system complexity while maintaining calibration precision
Solution Approach 2:
The laser system performs self-calibration using the integrated solid-state etalon and wavelength shift tracking device. The system monitors its own wavelength shifts and automatically corrects for drifts without requiring external calibration instruments, making the calibration process self-contained and eliminating mechanical instabilities associated with external devices
2Measurement precision
If complex and bulky etalons such as filters, gas cells or electronically tunable gratings are used, then wavelength calibration is achieved, but the device size and complexity increase
Solution Approach 1:
The patent replaces bulky mechanical etalons (filters, gas cells, electronically tunable gratings) with a solid-state etalon that has no moving parts. This solid-state implementation maintains the wavelength calibration function while dramatically reducing the physical size and eliminating mechanical complexity, making the system more compact and reliable
3Adaptability or versatility
If mechanical motors are used for cavity tuning, then wavelength tuning is achieved, but mechanical instabilities and drifts occur
Solution Approach 1:
The patent implements a feedback mechanism using the solid-state etalon and wavelength shift tracking device to monitor the laser wavelength in real-time. This feedback information is used to compensate for drifts and maintain accurate wavelength control, replacing reliance on mechanical motor stability with an optical feedback system that is inherently more stable and reliable
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 precise, low-cost, and virtually maintenance-free wavelength calibration of widely tunable lasers, applicable to both monolithic and hybrid architectures, facilitating applications like spectroscopic sensing and LIDAR without mechanical recalibration.
Implementation Method 1
an etalon such as an offset distributed Bragg reflector or any optical cavity... Due to the etalon's distinct, wavelength specific transmission/reflection function, the output signal at the etalon provides a distinct signal (either high or low) once the laser wavelength is tuned to the specific wavelength of the etalon
Implementation Method 2
the output of the wavelength shift tracking device, in the form of non-balanced interferometer records an oscillating periodic signal as a function of time
Implementation Method 3
Light emitted from the widely tunable laser is transmitted to the target object, the transmitted light interacting with molecules within the substance, and light-molecule interactions modifying spectral properties of the transmitted light
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3a
AI summary
Methods for wavelength determination of widely tunable lasers and systems thereof may be implemented with solid-state laser based photonic systems based on photonic integrated circuit technology as well as discrete table top systems such as widely-tunable external cavity lasers and systems. The methods allow integrated wavelength control enabling immediate system wavelength calibration without the need for external wavelength monitoring instruments. Wavelength determination is achieved using a monolithic solid-state based optical cavity with a well-defined transmission or reflection function acting as a wavelength etalon. The solid-state etalon may be used with a wavelength shift tracking component, e.g., a non-balanced interferometer, to calibrate the entire laser emission tuning curve within one wavelength sweep. The method is particularly useful for integrated photonic systems based on Vernier-filter mechanism where the starting wavelength is not known a-priori, or for compact widely tunable external cavity lasers eliminating the need for calibration of wavelength via external instruments.