Edge Emitting Semiconductor Laser Phase Structure
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Solution Overview
Problem
Edge emitting semiconductor lasers in the infrared spectral range face challenges in producing phase structures that effectively suppress higher lateral laser modes due to the concentration of laser radiation in the waveguide region and thick cladding layers, making it difficult to achieve efficient coupling of laser light into optical elements.
Innovation Solution
The design includes a phase structure with cutouts extending into the second cladding layer, incorporating intermediate layers of different semiconductor materials to facilitate precise etching and reduce refractive index abruptness, allowing for targeted suppression of higher modes and promotion of the lateral fundamental mode, thereby improving beam quality and coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase structures are formed by etching into the second cladding layer to suppress higher lateral laser modes, then beam quality and coupling efficiency are improved, but the etching depth must be very precisely defined which increases manufacturing difficulty
Solution Approach 1:
An intermediate layer with different etching properties is introduced between the second cladding layer and the waveguide region. This intermediate layer serves as a mediator that stops the etching process at a predetermined depth, eliminating the need for very precise etching depth control while still achieving the desired phase structure effect for suppressing higher lateral laser modes.
2Ease of operation
If deep etching structures are produced to achieve effective phase structures for infrared lasers, then mode selection is improved, but the requirements for etching depth precision and structure production become very difficult to fulfill simultaneously
Solution Approach 1:
The intermediate layer is prepared in advance during semiconductor layer formation, creating a predetermined etching stop depth before the actual phase structure etching is performed. This preliminary action ensures that when etching is performed later, the process automatically stops at the correct depth without requiring extreme precision, thus facilitating easier manufacture while maintaining effective mode selection.
3Power
If the active region width is increased to achieve high output power, then power output is improved, but a large number of lateral laser modes commence oscillation which worsens coupling efficiency
Solution Approach 1:
Phase structures are introduced locally in the second cladding layer above the active region to create position-dependent refractive index variations. These localized phase structures selectively suppress higher lateral laser modes while allowing the active region to maintain its broad width for high power output, thus resolving the contradiction between power and coupling efficiency.
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 approach enables high beam quality and efficient coupling of the lateral fundamental mode into optical fibers, even for semiconductor lasers emitting in the infrared range, by reducing coupling losses and promoting single-mode operation.
Implementation Method 1
The phase structures are regions of the semiconductor body in which the effective refractive index deviates from the effective refractive index of the regions of the semiconductor body that adjoin in a lateral direction
Data Source
AI summary
An edge emitting semiconductor laser includes a semiconductor body including a waveguide region, the waveguide region including first and second waveguide layers and an active layer arranged between the first and second waveguide layers, that generates laser radiation; the waveguide region is arranged between a first and second cladding layers disposed downstream of the waveguide region; a phase structure for selection of lateral modes of the laser radiation emitted by the active layer, wherein the phase structure includes at least one cutout extending from a top side of the semiconductor body into the second cladding layer; at least one first intermediate layer composed of a semiconductor material different from that of the second cladding layer embedded into the second cladding layer; and the cutout at least partly extends from the top side into the first intermediate layer; the second cladding layer contains a first partial layer adjoining the waveguide region.