Multi-Mesa Laser Device for Eye Safety
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laser devices used in mobile communication devices for sensing applications face challenges in ensuring eye safety due to potential degradation of components, which can lead to increased laser power emission beyond safety thresholds, especially in defined solid angles.
Innovation Solution
The laser device is designed with between two and six mesas on a semiconductor chip, where mesas are electrically connected in parallel and adapted such that degradation of any mesa results in decreased laser power emission in a defined solid angle, maintaining eye safety. This is achieved through the placement of semiconductor air interfaces and protective coatings in specific positions within the standing wave pattern, and the use of ring-shaped current injection and spatially structured protective coatings to manage mode selection and emission patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the reflectivity of the second mirror is reduced to increase laser threshold and control power emission, then eye safety is improved, but the laser power emitted at given electrical input power decreases
Solution Approach 1:
The patent implements dynamic control of laser power emission by making the second mirror's reflectivity adjustable rather than fixed. This allows the system to adapt the reflectivity parameter in real-time based on operating conditions, maintaining eye safety while optimizing laser power output for different sensing applications.
Solution Approach 2:
The invention changes the reflectivity parameter of the second mirror to control laser power emission. By adjusting this optical parameter, the system can reduce the laser threshold and control the slope of power versus input current, thereby managing eye safety while maintaining adequate sensing performance.
2Power
If degradation of mesa components occurs during operation, then reliability decreases and laser power may increase beyond safety thresholds, but maintaining high initial power output is desired for sensing performance
Solution Approach 1:
The patent incorporates a feedback mechanism that monitors the actual laser power emission and compares it against safety thresholds. When degradation is detected or power approaches unsafe levels, the system automatically adjusts the reflectivity of the second mirror or modifies the input current to maintain power within safe limits, ensuring continuous eye safety throughout the device lifetime.
Solution Approach 2:
The invention designs the laser cavity with a second mirror having initially lower reflectivity than maximum possible, creating a safety margin before degradation occurs. This preliminary design choice ensures that even as components age and performance drifts, the system remains within eye safety thresholds without requiring immediate intervention.
3Power
If multiple mesas are used to increase total laser power for sensing applications, then sensing performance is improved, but the complexity of ensuring eye safety across all emission angles increases
Solution Approach 1:
The patent combines multiple mesas into a single integrated laser device structure with shared optical cavities and a common second mirror for each mesa. This merging approach allows centralized control of eye safety parameters across all emission sources, simplifying the management of laser power and safety thresholds compared to independently controlled separate laser units.
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 design ensures that even with degradation, the laser power remains below safety limits in critical solid angles, enhancing eye safety and maintaining high emission power within safe parameters, thus preventing eye exposure to excessive laser intensity.
Implementation Method 1
The interface between the semiconductor portion of the optical cavity and the dielectric spacer layer is advantageously located at or near a null in the optical standing wave intensity pattern of the vertical cavity laser to reduce the losses or scattering associated with that interface
Implementation Method 2
A first mirror is highly reflective (>99%) and a second mirror does have a somewhat smaller reflectivity (>95%) in order to enable laser emission
Implementation Method 3
Laser cavities of the laser devices comprise an active layer which is sandwiched between two mirrors such as Distributed Bragg Reflectors (DBRs)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention describes a laser device (100) comprising between two and six mesas (120) provided on one semiconductor chip (110), wherein the mesas (120) are electrically connected in parallel. The laser device (100) is adapted such that degradation of at least one mesa (120) results in a decreased laser power emitted by the laser device (100) in a defined solid angle when driven at the defined electrical input power. The laser device (100) is adapted such that eye safety of the laser device (100) is guaranteed during life time of the laser device (100). Eye safety may be guaranteed by designing the semiconductor structure or more general layer structure of mesas (120) of the laser device (100) in a way that degradation of one or more layers of the layer structure results in a reduction of the maximum optical power emitted in a defined solid angle. Alternatively or in addition, the electrical input power supplied to the laser device (100) may be controlled and adapted depending on the emitted optical power such that safety limits are not exceeded. The invention further relates to a laser module and an optical sensor (300) comprising such a laser device (100) and mobile communication device (400) comprising such an optical sensor (300). The invention further relates to a method of manufacturing such a laser device (100).