External Cavity Tunable Laser with Matched Resonator FSR
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Solution Overview
Problem
Existing tunable lasers with external cavities face limitations in speed and power loss due to the need to tune phase shifters of linear resonators during wavelength tuning, which slows down the process and results in power loss.
Innovation Solution
A tunable laser design where the first resonator's resonance frequency is tuned while the second resonator's frequency is kept fixed, with the FSR of the second resonator matching the FSR of the entire cavity, allowing for fast wavelength tuning without power loss and eliminating the need to tune the phase shifter of the linear resonator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phase shifters of linear resonators are tuned during wavelength tuning, then wavelength can be adjusted across the cavity, but tuning speed is reduced and power loss occurs
Solution Approach 1:
The patent extracts the phase shifting function from the linear resonator system by introducing a dedicated phase shifter in the external cavity. This separates the wavelength selection function (performed by the tunable resonator in the external cavity) from the phase adjustment function (performed by the dedicated phase shifter), allowing fast wavelength tuning without requiring phase shifter operation during the tuning process itself.
Solution Approach 2:
The patent introduces an external cavity with a tunable resonator as an intermediary element between the linear resonator and the output. This external cavity acts as a wavelength-selective filter that can be tuned independently, allowing the linear resonator to maintain its phase settings while still achieving wavelength tuning through the external cavity's resonator.
2Adaptability or versatility
If phase shifters of linear resonators are tuned during wavelength tuning, then wavelength can be adjusted, but power loss occurs
Solution Approach 1:
The patent extracts the wavelength selection function from the linear resonator phase adjustment process and relocates it to a dedicated tunable resonator in the external cavity. This separation allows wavelength tuning to occur through resonator frequency adjustment rather than phase shifter operation, eliminating the associated power loss while maintaining full wavelength tuning capability.
3Speed
If the FSR of the second resonator is matched to an integer multiple of the cavity FSR, then fast tuning without power loss is achieved, but the design complexity increases
Solution Approach 1:
The patent applies parameter matching between the second resonator's FSR and the cavity's FSR (specifically, the second resonator's FSR is set to an integer multiple of the cavity FSR). This parameter relationship creates a synchronized tuning mechanism where the resonators' frequency responses align, enabling fast wavelength switching without power loss while maintaining a manageable design through systematic parameter relationships.
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 fast and efficient wavelength tuning across a wide range without power loss, as the second resonator's fixed frequency ensures consistent output power, overcoming the bottleneck of phase shifter tuning speed.
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
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
Data Source
AI summary
Examples include a tunable laser, in particular, an external cavity type laser. Examples also include a method of operating the tunable laser. The tunable laser is designed for fast and repeatable wavelength tuning over a wide wavelength range. The tunable laser includes a cavity and a gain medium arranged in the cavity. The gain medium is configured to generate light by stimulated emission and to emit the light into the cavity. The tunable laser also includes 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. A resonance frequency of the first resonator is tunable. A free spectral range (FSR) of the second resonator is an integer multiple of an FSR of the cavity.