Pre-distorted Laser Signal for High-Energy Optical Pulse Generation
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Solution Overview
Problem
Existing methods for generating high-energy optical pulses with arbitrary waveforms suffer from signal distortion due to the non-linear nature of optical amplifiers and frequency converters, limited energy storage, and limitations from stimulated Brillouin scattering, making it difficult to produce pulses with desired energy and waveform.
Innovation Solution
A system and method that pre-distorts a laser signal seed pulse before amplification and frequency conversion to compensate for expected distortions, using a combination of direct and indirect modulation of the laser signal, and a chain of amplifiers including broadband and narrowband stages to reduce gain clamping and ASE effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If optical amplifiers and frequency converters are used to increase energy level, then pulse energy is improved, but signal waveform distortion occurs
Solution Approach 1:
The patent applies pre-distortion to the input signal before it enters the nonlinear amplification and frequency conversion stages. By calculating and applying the inverse of the expected distortion in advance, the signal is pre-shaped to compensate for the nonlinear effects that will occur during amplification, thereby maintaining waveform accuracy while achieving high pulse energy
Solution Approach 2:
The pre-distortion process intentionally applies an opposite distortion to the input signal that counteracts the expected nonlinear distortion from the amplifier and frequency converter. This preliminary anti-action ensures that when the signal passes through the nonlinear stages, the cumulative effect results in the desired waveform shape at the output
2Use of energy by moving object
If amplifier energy storage is increased, then pulse energy is improved, but amplified spontaneous emission and parasitic coupling limit the storage capability
Solution Approach 1:
The patent employs a pulsed amplification scheme where the amplifier operates in discrete pulses rather than continuous operation. This allows the amplifier to be pumped and store energy between pulses, then release it in controlled bursts, achieving high pulse energy while managing the inherent limitations of amplifier energy storage through periodic operation
3Use of energy by moving object
If transmission capabilities are increased, then pulse energy is improved, but stimulated Brillouin scattering limits the transmission
Solution Approach 1:
The patent applies pre-distortion to the input signal that includes compensation for stimulated Brillouin scattering effects. By pre-shaping the signal waveform and frequency content, the system anticipates and counteracts the SBS limitations that will occur during high-energy transmission, enabling higher pulse energies to be achieved despite the presence of SBS
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 pre-distortion technique allows for the generation of high-energy optical pulses with desired waveforms and frequencies, reducing distortion and increasing pulse energy while mitigating stimulated Brillouin scattering, thereby achieving improved pulse contrast ratios.
Implementation Method 1
an intensity modulator configured to receive the laser output; and a second waveform generator configured to apply a second signal to the intensity modulator, the intensity modulator being configured to generate a pre-distorted laser signal based on the second signal and the laser output
Implementation Method 2
an amplifier coupled to the intensity modulator and configured to amplify the pre-distorted laser signal for generating the optical signal having the pre-selected waveform
Implementation Method 3
a frequency converter coupled to the intensity modulator and configured to convert a frequency of the pre-distorted laser signal for generating the optical signal having the pre-selected waveform
Implementation Method 4
The first waveform generator may be configured to apply the first signal to the laser source through a laser source driver configured to directly modulate a current applied to the laser source
Implementation Method 5
The laser source driver may be configured to directly modulate the current applied to the laser source by ramping the current applied to the laser source to generate a frequency chirp in the pre-selected waveform
Implementation Method 6
The pre-distorted laser signal may compensate for distortion caused by the amplifier and frequency converter
Implementation Method 7
The amplifier may include an optical gate between the stages to reduce gain clamping
Data Source
AI summary
A system for generating an optical signal having a preselected waveform includes: a laser source; a first waveform generator configured to apply a first signal to the laser source to create a laser output; an intensity modulator configured to receive the laser output; a second waveform generator configured to apply a second signal to the intensity modulator, the intensity modulator being configured to generate a pre-distorted laser signal based on the second signal and the laser output.