VCSEL Array Laser Source for High-Power Lidar
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Solution Overview
Problem
LIDAR systems, particularly FMCW LIDAR, require high-power laser light sources to reliably detect objects at greater distances, which existing single-mode lasers cannot efficiently provide.
Innovation Solution
A laser light source comprising a first semiconductor laser emitting pump radiation and an array of surface-emitting semiconductor lasers that absorb and amplify the pump radiation, with a polarization-rotating element and elliptical apertures, capable of emitting high-power laser radiation of a single optical mode with frequency modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single-mode laser is used to maintain beam quality and coherence, then the laser radiation has good directional properties and low noise, but the available laser power is insufficient for detecting objects at greater distances
Solution Approach 1:
The laser system is segmented into multiple independent VCSELs arranged in an array, where each VCSEL operates as an individual emitter. This segmentation allows the system to combine the output of multiple low-power sources to achieve high total power while maintaining the single-mode characteristics of individual emitters, thereby resolving the contradiction between power and detection reliability.
Solution Approach 2:
Multiple VCSEL outputs are merged into a single beam path using optical combining techniques. The individual laser beams from each VCSEL are spatially and temporally synchronized to form a coherent combined beam, achieving high power output with maintained beam quality and coherence, thus enabling reliable long-distance object detection.
2Power
If an array of surface-emitting semiconductor lasers is used to increase power, then high-power laser radiation can be achieved, but maintaining single-mode emission and reducing noise becomes difficult
Solution Approach 1:
The system performs preliminary frequency locking and phase synchronization of all VCSELs before combining their outputs. By pre-establishing coherent relationships between individual emitters through external cavity locking and feedback mechanisms, the system ensures that when beams are combined, they interfere constructively rather than creating noise, thus achieving high power with low noise.
Solution Approach 2:
The system implements feedback control mechanisms where the combined beam characteristics are monitored and used to adjust the operating parameters of individual VCSELs. This feedback loop maintains optimal coherence and phase relationships, minimizing noise while maximizing power output, thereby resolving the contradiction between high power and low noise.
3Power
If multiple semiconductor lasers are combined to increase power, then high-power output is achieved, but the device structure becomes more complex
Solution Approach 1:
The VCSEL array structure serves multiple functions simultaneously: it provides power scaling, maintains beam quality, enables frequency modulation, and facilitates coherent combining. This multi-functionality reduces the need for additional separate components, thereby managing device complexity while achieving high power output.
Solution Approach 2:
The system employs a nested structure where individual VCSELs are integrated into a common substrate or housing, which itself is integrated into a larger optical assembly. This nesting approach consolidates multiple components into compact arrangements, reducing overall device complexity while maintaining the high-power capability of the multi-VCSEL configuration.
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 solution enables the production of high-power laser radiation with reduced noise, allowing for reliable object detection at greater distances while maintaining a simple and cost-effective structure.
Implementation Method 1
an array of surface-emitting semiconductor lasers adapted to absorb the pump radiation and emit laser radiation at a frequency of the pump radiation
Implementation Method 2
a polarization-rotating element, which is arranged between the first semiconductor laser and a part of the surface-emitting semiconductor laser
Data Source
AI summary
The invention relates to a laser light source (10), comprising an arrangement (120) of surface-emitting semiconductor lasers (1251, 1252, . . . 125n) to which a voltage is applied such that an operating current is below the threshold current and an intrinsic emission of the surface-emitting semiconductor laser is prevented. The laser light source also comprises a first semiconductor laser (100) which emits radiation (110) that enters the surface-emitting semiconductor laser such that induced emission takes place via the injection locking mechanism and the individual surface-emitting semiconductor lasers emit laser light having the same wavelength and polarisation direction as the irradiated radiation (110). The emission frequency of the first semiconductor laser can be changed by changing the operating current.