Surface-Emitting Quantum Cascade Laser With Sidewall Fabry-Perot Resonance
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Solution Overview
Problem
The oscillation threshold current of surface-emitting quantum cascade lasers increases due to manufacturing fluctuations causing the oscillation wavelength to shift from the peak wavelength of the gain curve of the light-emitting layer.
Innovation Solution
Incorporating a reflective film at the sidewalls of the mesa portion to induce resonance via a Fabry-Perot resonator, aligning the oscillation wavelength with the gain peak using a photonic crystal layer and a two-dimensional diffraction grating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a photonic crystal layer with a two-dimensional diffraction grating is used to control the oscillation wavelength, then surface emission is enabled, but the oscillation threshold current increases when the oscillation wavelength shifts from the peak wavelength of the gain curve due to manufacturing fluctuation
Solution Approach 1:
A reflective film is introduced as an intermediary component between the light-emitting layer and the external environment. This reflective film forms a Fabry-Perot resonator cavity that provides wavelength-selective feedback, enabling the laser to maintain low threshold current operation even when the photonic crystal layer's controlled wavelength shifts due to manufacturing variations. The reflective film mediates the interaction between the gain medium and the optical field, ensuring stable oscillation at the desired wavelength.
Solution Approach 2:
The invention changes the optical parameters of the system by introducing a reflective film with specific reflectivity characteristics at the sidewalls of the mesa portion. This creates a Fabry-Perot resonator with controlled cavity length and reflectivity, thereby adjusting the resonant wavelengths to coincide with the peak gain wavelength. This parameter adjustment compensates for manufacturing fluctuations in the photonic crystal layer, maintaining optimal oscillation conditions.
2Measurement precision
If the oscillation wavelength is controlled by the photonic crystal layer, then surface emission direction is controlled, but manufacturing fluctuation causes wavelength shift from the peak gain curve
Solution Approach 1:
The reflective film creates an optical feedback mechanism through the Fabry-Perot resonator effect. This feedback system selectively reinforces optical modes that resonate within the cavity formed by the reflective film and the photonic crystal layer, providing wavelength stabilization. When manufacturing fluctuations cause the photonic crystal layer to shift the controlled wavelength, the Fabry-Perot resonator provides feedback that maintains oscillation at the resonant wavelength, compensating for the manufacturing imprecision.
3Use of energy by moving object
If a reflective film is added at the sidewalls to induce Fabry-Perot resonance, then threshold current is reduced, but device complexity increases
Solution Approach 1:
The reflective film is applied locally only at the sidewalls of the mesa portion rather than throughout the entire device structure. This localized application provides the necessary Fabry-Perot resonance effect for threshold current reduction while minimizing the increase in device complexity. The reflective film is positioned specifically where it can form the resonator cavity with the photonic crystal layer, providing maximum benefit with minimal added structural complexity.
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
Reduces the oscillation threshold current and enables efficient surface emission by aligning the oscillation wavelength with the gain peak, particularly effective in low light output regions.
Implementation Method 1
a light-emitting layer emitting light due to an intersubband transition of a carrier
Implementation Method 2
a photonic crystal layer including a two-dimensional diffraction grating
Implementation Method 3
Incorporating a reflective film at the sidewalls of the mesa portion to induce resonance using a Fabry-Perot resonator
Data Source
AI summary
According to one embodiment, a surface-emitting quantum cascade laser includes a substrate; a mesa portion of a semiconductor stacked body located on the substrate, and a reflective film located at a sidewall of the mesa portion. The mesa portion includes a light-emitting layer emitting light due to an intersubband transition of a carrier, and a photonic crystal layer including a two-dimensional diffraction grating.