Semiconductor Laser Device Wide Emission Wavelength Band
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Solution Overview
Problem
Existing semiconductor laser devices have limited wavelength range for infrared light emission, which restricts their application in gas measurement and analysis.
Innovation Solution
A semiconductor laser device is designed with multiple unit stacked bodies having different quantum well layer widths, allowing for intersubband transitions and spatial periodicity to achieve a wide emission wavelength band, enabling efficient infrared light emission across a broader spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single quantum well layer width is used in the semiconductor laser device, then the device structure is simple and easy to manufacture, but the emission wavelength range is limited
Solution Approach 1:
The active layer is segmented into multiple quantum well layers with different well widths (e.g., 5 nm, 7 nm, 9 nm) stacked alternately. Each quantum well layer contributes to emission at different wavelengths, thereby expanding the overall emission wavelength range while maintaining a manageable layered structure that can be fabricated using standard semiconductor manufacturing techniques.
Solution Approach 2:
Different quantum well layers are designed with different local properties (different well widths) to optimize emission at specific wavelengths. The first quantum well layer has a width optimized for one wavelength range, while the second quantum well layer has a different width optimized for another wavelength range, allowing the device to cover a broad spectrum through localized property variation.
2Adaptability or versatility
If multiple quantum well layers with different widths are stacked, then the emission wavelength band is widened, but the device structure becomes more complex
Solution Approach 1:
Multiple quantum well layers with different well widths are merged into a single active layer structure. The first and second quantum well layers are alternately stacked to form a unified active layer that functions as an integrated multi-wavelength emission source, combining the capabilities of different well width configurations in one device.
Solution Approach 2:
The active layer is designed to perform multiple functions by incorporating quantum well layers with different well widths. This multi-functional structure enables the single device to emit across a wide wavelength range (e.g., 5-12 μm), making it universally applicable for detecting various gases with different absorption characteristics without requiring multiple separate laser devices.
3Adaptability or versatility
If the quantum well layer well width is increased, then the emission wavelength shifts to longer wavelengths, but the emission intensity may decrease
Solution Approach 1:
The quantum well layers are arranged in a periodic alternating pattern (first quantum well layer, second quantum well layer, first quantum well layer, etc.) along the growth direction. This periodic structure ensures that electrons undergo intersubband transitions at regular intervals, maintaining consistent emission intensity across different wavelength regions while enabling wavelength tuning through the alternating well width pattern.
Solution Approach 2:
The alternately stacked quantum well layers with different well widths create a continuous emission spectrum without gaps. The electron transport and intersubband transition processes continue seamlessly across all quantum well layers, ensuring that emission intensity is maintained across the entire wavelength range from short to long wavelengths, avoiding intensity drops that would occur with discrete separate emitters.
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 device achieves a wide emission wavelength band, enhancing gas measurement capabilities by allowing for precise detection of various gases through infrared light absorption analysis, reducing the need for multiple lasers and enabling device miniaturization.
Implementation Method 1
The quantum cascade laser has a structure where both side surfaces of the active layer are interposed between, for example, InP cladding layers. In this case, the cascade-connected quantum well layer is capable of emitting infrared laser light with a wavelength of 4 to 20 μm by intersubband transition of a carrier.
Implementation Method 2
Various gases included in air have an absorption spectrum peculiar to the gas due to infrared ray radiation. For this reason, type and concentration of the gas can be known by measuring an infrared ray absorption amount.
Data Source
AI summary
According to one embodiment of the invention, a semiconductor laser device includes a plurality of first unit stacked bodies and a plurality of second stacked bodies. The plurality of first unit stacked bodies have an emission region including a first quantum well layer and capable of emitting a first infrared light by an intersubband transition, and an electron injection region capable of transporting an electron relaxed to a mini-band level in the emission region to a downstream unit stacked body. The plurality of second unit stacked bodies have an emission region including a second quantum well layer and capable of emitting a second infrared light by an intersubband transition, and an electron injection region capable of transporting an electron relaxed to a mini-band level in the emission region of the second quantum well layer to a downstream unit stacked body. The second quantum well layer has at least one well width different from a well width of the first quantum well layer. The first unit stacked body and the second stacked body are stacked with spatial periodicity.