Passively Mode-Locking Semiconductor Disk Laser Resonator Field Area
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Solution Overview
Problem
Existing passively mode-locking semiconductor disc lasers lack stability in generating ultra short pulses, as they rely on saturable absorber mechanisms that are not always self-starting and require precise adjustments, leading to instability in pulse generation.
Innovation Solution
A passively mode-locking semiconductor disc laser design with a resonator configuration where the cross sectional area of the intra cavity resonating field on the intensity saturable mirror is greater than or equal to that on the multilayer semiconductor gain medium, utilizing a saturable Bragg reflector to clip pulse edges and enhance gain saturation, thereby increasing stability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a saturable absorber mechanism is used for passive mode locking, then ultra short pulse generation is achieved, but the system lacks stability and is not self-starting
Solution Approach 1:
The patent changes the physical parameters of the saturable absorber by using a saturable Bragg reflector with specific reflectivity characteristics. The reflectivity is modulated through the saturable absorption effect in the quantum well layer, creating intensity-dependent loss modulation that enables stable passive mode locking without requiring precise manual adjustment.
Solution Approach 2:
The patent employs a composite structure combining a Bragg reflector with a saturable absorber layer (quantum well) to create a saturable Bragg reflector. This composite component integrates the high reflectivity of the Bragg mirror with the intensity-dependent absorption of the quantum well, achieving both self-starting capability and stable pulse generation.
2Reliability
If the cross sectional area of the intra cavity resonating field on the gain medium is increased, then gain saturation is reduced, but the mode locking stability deteriorates
Solution Approach 1:
The patent applies local quality by creating different field distribution characteristics in different parts of the cavity. The saturable Bragg reflector is positioned to experience higher intensity than the gain medium, creating local intensity enhancement at the mirror location. This localized intensity difference enables the saturable absorber to effectively modulate losses while maintaining adequate gain saturation in the amplification region.
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 achieves increased stability and reliability in generating ultra short pulses, with pulse widths ranging from 100 ps to 100 fs, by ensuring the intensity saturable mirror effectively clips pulse edges and adjusts gain saturation, outperforming conventional systems.
Implementation Method 1
Passive mode locking generally relies on a saturable absorber mechanism, which produces decreasing loss with increasing optical intensity
Implementation Method 2
An SBR is a nonlinear mirror that comprises one or more semiconductor quantum wells within a standard distributed Bragg reflector (DBR)
Data Source
AI summary
A passively mode-locking laser and corresponding method is described. The laser comprises a resonator (2) terminated by first (3) and second (4) mirrors and folded by a third (5) and fourth (6) mirror. The third mirror comprises a reflector (14) surmounted by a multilayer semiconductor gain medium (15) including at least one quantum well layer while the second mirror (4) comprises an intensity saturable mirror. The resonator is configured to provide a cross sectional area of an intra cavity resonating field on the intensity saturable mirror that is greater than or equal to a cross sectional area of the intra cavity resonating field on the multilayer semiconductor gain medium. This arrangement provides a passively mode-locking laser that exhibits increased stability when compared to those systems known in the art.