Ultrafast Pulse Laser Intensity Correction for Pulse Distortion
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Solution Overview
Problem
Ultrafast pulse lasers experience pulse distortion due to self-phase modulation, leading to increased pulse duration and reduced peak power, which is problematic for applications requiring high pulse energy and peak power.
Innovation Solution
The ultrafast pulse fiber laser system employs a fast intensity modulator driven by a corrected electrical signal to correct the spectral intensity profile of chirped pulses, using a Mach-Zehnder Lithium Niobate or Indium Phosphide Modulator and high-speed electronics to suppress pulse distortion and achieve a parabolic spectral shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high peak power pulses are used to increase pulse energy, then pulse energy is improved, but pulse distortion increases due to self-phase modulation
Solution Approach 1:
The patent applies preliminary action by pre-chirping the pulse before amplification, which stretches the pulse in time and reduces peak power during the nonlinear interaction with gain material. This preliminary stretching prevents excessive nonlinear phase accumulation while maintaining the ability to achieve high final pulse energy through subsequent compression
Solution Approach 2:
The patent changes the temporal and spectral parameters of the pulse by introducing chirp (frequency modulation across the pulse duration). This parameter transformation allows the pulse to tolerate higher energies by distributing the energy over a longer time period during amplification, then recompressing to achieve the desired high peak power and energy in the final output
2Object-affected harmful factors
If pulse duration is increased to reduce peak power and suppress SPM, then nonlinear effects are reduced, but pulse energy extraction capability is limited
Solution Approach 1:
The patent performs preliminary chirping to stretch the pulse before amplification, which temporarily increases pulse duration to suppress nonlinear effects during the amplification process. After amplification, the pulse is compressed back to its original short duration, thereby achieving both suppression of nonlinear effects during amplification and high pulse energy extraction in the final output
3Use of energy by moving object
If chirped pulse amplification is used to extract higher pulse energy, then pulse energy is improved, but pulse duration increases due to accumulated nonlinear phase shifts
Solution Approach 1:
The patent applies preliminary chirping with controlled dispersion to stretch the pulse before amplification. By carefully managing the amount of chirp and using appropriate compression elements afterward, the system achieves high pulse energy extraction while minimizing the final pulse duration, thus resolving the contradiction between energy extraction and pulse duration maintenance
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
This configuration effectively suppresses pulse distortion, maintaining high peak power and pulse energy by correcting spectral ripples and achieving near transform-limited pulses, suitable for applications requiring high pulse energies.
Implementation Method 1
an optoelectronic converter to convert the received second portion of light signal into an electrical signal
Implementation Method 2
The electrical signal is coupled into at least one radio-frequency (RF) generator scheme which processes the electrical signal applied to the intensity modulator
Implementation Method 3
In this method the pulse are stretched in time by adjusting the phase of each longitudinal mode within the spectral envelope. Bulk gratings, prisms, fiber, chirped fiber Bragg gratings or chirped volume Bragg gratings can be used to stretch the pulses by introducing this dispersion.
Implementation Method 4
Laser machining using ultrashort pulses work on the principle of cold ablation via multiphoton absorption
Implementation Method 5
When ultrashort optical pulses propagate through any material with a non-zero nonlinear index of refraction there is an accumulation of nonlinear phase shifts through the process of SPM
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3B
AI summary
The ultrafast pulse fiber laser system is configured with scalable output power and operative to reduce degradation of pulse integrity. The disclosed laser system is configured to suppress the pulse distortion through improvement of initial pulse contrast between main and side pulses and improved pulse shape using chirped pulse amplification and a fast intensity modulator driver by a corrected electrical signal that is generated from the original optical signal. The structure providing the improvement includes the photodiode, which is operative to measure the chirped optical pulse and convert it to the electrical signal, and analog electronics that quickly converts the electrical signal to the required signal that suppress the side pulses.