Multi-Section Laser Pre-Biasing for Broad Linewidth Pulses
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Solution Overview
Problem
Conventional mixed-reality systems face challenges in providing high-quality virtual images due to fringe image artifacts caused by narrow spectral linewidth of traditional lasers, which impair user experience and require improved resolution.
Innovation Solution
A multi-section laser with a gain/modulation section and a pre-bias section, controlled by laser driver circuitry, is used to reduce turn-on delay and increase spectral linewidth, generating laser light with a broadened spectral range to reduce fringe artifacts and enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional lasers with narrow spectral linewidth are used, then laser coherence is maintained, but fringe image artifacts (Newton Rings) are introduced into virtual images
Solution Approach 1:
The laser is divided into multiple independent sections (first section, second section, third section) along the waveguide. Each section can be independently controlled with different current levels, allowing the first section to operate below threshold (reducing coherence) while the second and third sections provide gain and output. This segmentation enables independent optimization of coherence and artifact reduction.
Solution Approach 2:
Different sections of the laser are assigned different operational characteristics. The first section operates below threshold with lower current to reduce coherence and minimize fringe artifacts, while the second and third sections operate above threshold with higher current to provide optical gain and maintain necessary laser performance. Each section has optimized current levels tailored to its specific function.
2Productivity
If traditional single-section lasers are used, then device complexity is low, but turn-on delay is excessive for high-resolution virtual image rendering
Solution Approach 1:
The laser structure is segmented into multiple independently controllable sections with separate current control circuits. This allows the first section to be pre-biased below threshold to prepare photons in advance, enabling faster turn-on when the second section is activated. The segmentation enables parallel preparation and rapid switching.
Solution Approach 2:
The first section is pre-biased with a current below the threshold level before the laser pulse is needed. This preliminary action prepares photons in the waveguide in advance, so that when the second section is activated above threshold, the laser pulse can start immediately without the usual turn-on delay, achieving faster response for high-resolution rendering.
3Power
If traditional lasers operate above threshold continuously, then sufficient optical power is available, but power consumption is high
Solution Approach 1:
The laser is segmented into multiple sections with independent current control, allowing only the necessary sections to operate above threshold. The first section operates below threshold consuming minimal power, while the second and third sections provide gain and output only when needed. This segmentation enables selective activation to reduce overall power consumption.
Solution Approach 2:
Instead of operating the entire laser above threshold continuously, only the second and third sections are activated above threshold when optical output is needed, while the first section remains below threshold. This partial action approach provides sufficient optical power for virtual image rendering while minimizing power consumption by keeping part of the laser inactive.
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 significantly reduces turn-on delay to less than 1 nanosecond, achieves a broader spectral linewidth, and decreases power consumption, resulting in improved virtual image quality and user experience by minimizing fringe artifacts and increasing resolution.
Implementation Method 1
Applying this pre-bias current causes photons to be spontaneously emitted
Implementation Method 2
laser driver circuitry... applies current to the pre-bias section... applies the gain current to the gain section to generate a seeded pulse of laser light
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
Multi-section laser systems are configured with a gain/modulation section and a pre-bias section. Both sections are electrically connected to a diode laser resonator and both sections are independently controllable via laser driver circuitry. The multi-section laser can be used to provide pulsing optimizations that include reducing the turn-on delay of the laser while also ensuring that the resulting laser light's spectral linewidth satisfies a threshold linewidth requirement. During use, a pre-bias current is applied to the pre-bias section. This current causes some photons to be spontaneously emitted. During this time, a gain current is refrained from being applied to the gain section until the resonator is seeded with a spectrum of photons from the pre-bias section. Once the resonator is sufficiently seeded, the gain current is applied to the gain section, thereby producing a seeded pulse of laser light having a desired spectral linewidth.