External Cavity Tunable Laser for Fast Wavelength Switching
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Solution Overview
Problem
Existing tunable lasers with external cavities face a bottleneck in tuning speed due to the need to phase-tune a linear resonator for each wavelength, leading to power loss and impractical switching from lowest to highest wavelengths.
Innovation Solution
A tunable laser design where the second resonator's free spectral range is an integer multiple of the entire cavity's free spectral range, allowing the first resonator to be tuned while keeping the second resonator stationary, eliminating the need for phase-shifting the linear resonator and enabling fast wavelength tuning without power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phase tuning of the linear resonator is performed for each wavelength, then wavelength tuning is achieved, but tuning speed is reduced and power loss occurs
Solution Approach 1:
The patent extracts the wavelength tuning function from the linear resonator phase shifter and concentrates it in the ring resonator phase shifter. By removing the tuning requirement from the linear resonator, the bottleneck in tuning speed is eliminated while maintaining full wavelength tuning capability through the ring resonator alone.
Solution Approach 2:
The patent introduces an intermediary mechanism (the specific FSR relationship between second resonator and cavity) that allows the first resonator to be tuned independently without requiring simultaneous adjustment of the linear resonator. This intermediary relationship mediates between the tuning action and the power loss problem.
2Reliability
If phase tuning of the linear resonator is performed for each wavelength, then wavelength fitting in cavity is achieved, but power loss occurs
Solution Approach 1:
The patent extracts the wavelength fitting function from the linear resonator and transfers it to the ring resonator. The condition that the FSR of the second resonator is an integer multiple of the cavity FSR ensures that wavelengths selected by the ring resonator automatically fit the linear resonator without requiring active phase tuning, thereby eliminating power loss.
3Adaptability or versatility
If multiple phase shifters are used for tuning, then wavelength control is improved, but device complexity increases
Solution Approach 1:
The patent removes the phase shifter from the linear resonator path, reducing the total number of phase shifters required. The wavelength control function is extracted and consolidated in the ring resonator phase shifter, simplifying the overall device architecture while maintaining precise wavelength control.
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 design allows for rapid and efficient wavelength tuning across a wide range without power loss, as the first resonator can be tuned independently, enhancing the overall speed and practicality of the tunable laser system.
Implementation Method 1
a gain medium arranged in a region of the cavity, the gain medium being configured to generate light by stimulated emission and to emit the light into the cavity
Implementation Method 2
a first resonator and a second resonator that are optically coupled to each other, wherein a resonance frequency of the first resonator is tunable
Implementation Method 3
The external cavity allows making use of the well-known Vernier effect, which can effectively increase the tunability of the laser, while decreasing the linewidth and further enhancing the spectral purity
Data Source
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AI summary
The present disclosure relates to a tunable laser, in particular, an external cavity type laser. The disclosure also relates to a method of operating the tunable laser. The tunable laser of this disclosure is designed for fast and repeatable wavelength tuning over a wide wavelength range. The tunable laser comprises a cavity, a gain medium arranged in a region of the cavity, the gain medium being configured to generate light by stimulated emission and to emit the light into the cavity, and a laser output configured to output a portion of the light in the cavity as a laser beam. The cavity includes a first resonator and a second resonator that are optically coupled to each other, wherein a resonance frequency of the first resonator is tunable. A free spectral range (FSR) of the second resonator is an integer multiple of a FSR of the cavity.