Multi-Pass Bragg Grating Pulse Stretcher
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Solution Overview
Problem
Current systems for stretching and compressing laser pulses, such as those using fiber Bragg gratings, have limited adjustable range and can suffer damage from mechanical stress, restricting the extent of pulse length modification.
Innovation Solution
A CPA system employing multiple passes through various types of Bragg gratings, including fiber and volume Bragg gratings, with beam steering optics to control the number of passes and direction, allowing for greater flexibility and precision in stretching and compressing pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fiber Bragg grating is physically stretched to adjust pulse length, then pulse length adjustment is achieved, but optical fiber may suffer damage from physical stress and strain
Solution Approach 1:
The patent applies dynamics by making the Bragg grating adjustable through multiple passes instead of fixed physical dimensions. The system dynamically changes the effective grating length by controlling the number of passes (1, 2, or 4 passes) through the grating, allowing pulse stretching/compression ratios to be varied from 0.25 to 4 times without physically stressing the fiber.
Solution Approach 2:
The patent implements nesting by having the optical pulse pass through the same Bragg grating multiple times in sequence. Each pass through the grating accumulates additional dispersion, effectively nesting the grating's dispersive action within itself. This allows a single physical grating to provide variable stretching/compression by controlling the number of nested passes.
2Adaptability or versatility
If multiple passes through Bragg grating are used, then pulse stretching and compression capability is enhanced, but device complexity increases
Solution Approach 1:
The patent applies universality by designing a single Bragg grating that performs multiple functions: it can stretch pulses, compress pulses, and provide variable dispersion compensation. By controlling the number of passes (1-4 passes), the same grating system adapts to different pulse manipulation requirements, eliminating the need for multiple separate gratings of different sizes.
Solution Approach 2:
The patent merges multiple dispersive elements into a single physical Bragg grating by having the pulse pass through it multiple times. Instead of combining several separate gratings, the system combines the dispersive effect of one grating applied repeatedly, reducing the number of physical components while achieving the same cumulative effect.
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
Enables more significant and controlled stretching and compression of laser pulses, enhancing amplification capabilities while minimizing damage to optical components.
Implementation Method 1
the duration of the pulse is increased by first dispersing the ultrashort laser pulse temporally as a function of wavelength (a process called 'chirping')
Implementation Method 2
beam steering optics to control the number of passes and direction
Implementation Method 3
beam steering optics to control the number of passes and direction
Data Source
AI summary
A chirped pulse amplification (CPA) system and method is described wherein the pulse is stretched using multiple passes through a Bragg grating or compressed using multiple passes through a Bragg grating. A switch may be used to control the number of passes through the Bragg grating, thus, tuning the compressed or the stretched pulse width. The pulse may be directed through an amplifier between the multiple passes through the Bragg grating to apply amplification to the stretched pulse multiple times. The Bragg grating may include a fiber Bragg grating, a volume Bragg grating, or a Bragg waveguide.