External Resonator Light Emitting Device Wavelength Stability
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Solution Overview
Problem
Existing external resonator type light emitting systems face challenges with mode hopping, leading to instability in wavelength and optical power deviation due to temperature changes, requiring complex temperature control mechanisms like Peltier devices, which increase size and cost.
Innovation Solution
The design incorporates a grating device with a ridge type optical waveguide and a Bragg grating formed on a substrate, where the reflectance of the Bragg grating is higher than the antireflection films, and the length of the grating and active layer is optimized to minimize temperature-dependent wavelength changes, allowing for stable operation without a Peltier device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Peltier device is used for temperature control, then wavelength stability is improved, but device complexity and size increase
Solution Approach 1:
The patent extracts the temperature control function from the laser system by removing the Peltier device, achieving temperature-independent operation through optical design. The external resonator and grating configuration inherently compensates for temperature effects without active cooling/heating mechanisms.
Solution Approach 2:
The patent changes the operational parameters by designing the external resonator length and grating characteristics to provide temperature compensation. The resonator length and refractive index are selected such that the temperature coefficient of the resonant wavelength becomes zero, eliminating the need for active temperature control.
2Reliability
If a Peltier device is used for temperature control, then wavelength stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the Peltier device from the system, eliminating its cost while maintaining wavelength stability through passive optical design. The external resonator configuration with carefully selected parameters provides inherent temperature compensation.
Solution Approach 2:
The patent replaces expensive active temperature control components with a simple, passive optical resonator structure that provides temperature compensation at minimal cost, using only standard optical components.
3Reliability
If the resonator length is increased to improve wavelength stability, then mode hopping is reduced, but the device size increases
Solution Approach 1:
The patent optimizes the resonator length parameter to achieve temperature compensation. By selecting a specific resonator length that satisfies the temperature-independent condition, the system achieves wavelength stability without requiring excessive resonator length, thus avoiding unnecessary size increase.
Solution Approach 2:
The patent uses a composite structure combining the semiconductor laser with an external resonator containing a diffraction grating. This composite configuration enables temperature compensation through the combined optical path, achieving wavelength stability in a compact form factor.
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 configuration reduces mode hopping, enhances wavelength stability, and maintains optical power consistency across a broader temperature range, achieving a compact and cost-effective resonator structure.
Implementation Method 1
concaves and convexes are formed on a surface of a waveguide extended from a waveguide of the active layer to provide a mirror utilizing Bragg reflection for realizing a resonator
Implementation Method 2
a part of the propagating light is reflected by the diffraction gratings, returned into a current injection part and then amplified. As light component having only a single wavelength is reflected at a specific direction from the diffraction grating, the wavelength of the laser light is made constant.
Data Source
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AI summary
An external resonator type light emitting system includes a light source oscillating a semiconductor laser light and a grating device providing an external resonator with the light soruce. The light source includes an active layer oscillaing the semiconductor laser light. The grating device includes an optical waveguide having an incident face to which the semiconductor laser is incident and an emitting face of emitting an emitting light of a desired wavelength, a Bragg grating formed in the optical waveguide, and a propagating portion provided between the incident face and the Bragg grating. Formulas (1) to (4) are satisfied.