External Resonator Laser Wavelength Stability via Grating Design
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Solution Overview
Problem
Existing external resonator type semiconductor lasers experience mode hopping and wavelength instability due to temperature changes, leading to deviations in optical power, which are typically addressed by using a Peltier device, increasing the complexity and cost of the system.
Innovation Solution
An external resonator type light emitting system with a grating device that includes a Bragg grating and an optical waveguide, where specific design parameters such as Bragg reflectance full width at half maximum, grating length, active layer length, and refractive index are optimized to reduce mode hopping and improve wavelength stability without the need for a Peltier device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Peltier device is used to control temperature and prevent mode hopping, then wavelength stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the temperature control function from the laser system by removing the Peltier device, and instead incorporates temperature compensation directly into the resonator structure through the specific refractive index material and optimized geometric parameters, thereby simplifying the device while maintaining wavelength stability
Solution Approach 2:
The patent changes the physical parameters of the resonator by selecting a specific refractive index range (1.30-1.60) and optimizing the ratio between resonator length and grating length, which fundamentally alters the temperature dependency characteristics of the system to eliminate mode hopping without active cooling
2Reliability
If a Peltier device is used to maintain wavelength stability, then optical power stability is improved, but the system becomes less compact and more expensive
Solution Approach 1:
The patent merges the temperature compensation function with the resonator structure itself by integrating the specific refractive index material and optimized geometric ratios directly into the optical path, eliminating the need for separate temperature control components and achieving a more compact design
3Reliability
If the resonator length and grating length are optimized with specific ratios, then mode hopping is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges (refractive index: 1.30-1.60, length ratio: 0.3-2.0) that provide a manufacturing window, allowing tolerance for variation while still achieving the desired temperature compensation effect and mode hopping reduction
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
The system achieves reduced mode hopping and improved optical power stability over a wider temperature range, reducing the deviation of optical power and eliminating the need for a Peltier device, resulting in a more compact and cost-effective resonator structure.
Implementation Method 1
a mirror utilizing Bragg reflection for realizing a resonator
Implementation Method 2
light component having only a single wavelength is reflected at a specific direction from the diffraction grating
Data Source
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 source. The light source includes an active layer oscillating 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.