Optical Semiconductor Laser Layout With Ring Resonator Feedback
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Solution Overview
Problem
The configuration of optical filters in existing semiconductor lasers increases device size and limits the reduction of frequency noise across a wide frequency range due to phase delay and resonator length constraints, hindering miniaturization and stability of oscillation modes.
Innovation Solution
An optical semiconductor element comprising a semiconductor laser, an optical waveguide, and a ring resonator or DBR grating, with a controlled distance between the laser and the resonator or grating within 1 μm to 200 μm, allowing for optical coupling and feedback to reduce frequency noise through amplitude fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resonator loss is suppressed and the Q value of the resonator is increased, then the line width of the laser is narrowed, but spatial hole burning occurs causing carrier density decrease and refractive index distribution which leads to unstable oscillation mode
Solution Approach 1:
The patent introduces an optical feedback mechanism using an external mirror to return reflected light to the semiconductor laser. This feedback system stabilizes the oscillation mode by compensating for the effects of spatial hole burning, allowing the laser to maintain stable operation even with high Q-value resonators that produce narrow line widths.
2Stability of the object's composition
If the coupling coefficient of the diffraction grating is reduced to suppress spatial hole burning, then the oscillation mode stability is improved, but a long resonator length of several mm is required which hinders miniaturization
Solution Approach 1:
The patent combines the semiconductor laser with an external mirror system to create an integrated optical feedback structure. This merging allows the resonator length to be reduced to sub-millimeter scales while maintaining oscillation mode stability through the feedback mechanism, enabling miniaturization without sacrificing performance.
3Volume of stationary object
If existing optical filter configurations are used, then the device size is reduced, but frequency noise cannot be reduced across a wide frequency range due to phase delay and resonator length constraints
Solution Approach 1:
The patent extends the optical path by introducing an external mirror system that reflects light back through the resonator multiple times. This dimensional extension of the optical path allows for wide frequency range noise attenuation while keeping the physical device size compact, as the effective optical length is increased without proportionally increasing the physical footprint.
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 enables a compact optical semiconductor element that effectively reduces frequency noise across a wide frequency range, enhancing miniaturization and stability while maintaining high frequency noise attenuation without causing damping.
Implementation Method 1
use of a light feedback effect can be mentioned. In this effect, the external mirror is formed in the semiconductor laser, and the reflected light from the mirror is returned to the semiconductor laser, so that the line width can be narrowed
Implementation Method 2
an optical semiconductor element comprising a semiconductor laser, an optical waveguide, and a ring resonator or DBR grating, with a controlled distance between the laser and the resonator or grating within 1 μm to 200 μm, allowing for optical coupling and feedback
Implementation Method 3
phase inversion is performed by a phase shifter formed in a part of a uniform diffraction grating, and single mode oscillation at a Bragg wavelength is enabled
Implementation Method 4
a diffraction grating having a λ/4 phase shift has been used
Implementation Method 5
when the resonator loss is suppressed and the Q value of the resonator is increased, the light is strongly localized in the phase shift region
Implementation Method 6
A phenomenon in which a carrier distribution occurs in a resonator due to a light intensity distribution in laser as described above is called spatial hole burning
Data Source
AI summary
An optical semiconductor element includes, in order, a semiconductor laser, an optical waveguide, a loop waveguide, and a ring resonator optically coupled to the loop waveguide, in which a distance between the semiconductor laser and the ring resonator is 1 μm or more and 200 μm or less.