Ring Optical Circuit for Wide-Range Laser Pulse Duration Control
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Solution Overview
Problem
Current laser systems struggle to achieve a wide range of pulse duration tuning from femtoseconds to nanoseconds with precise control, while maintaining low coherence length and independent pulse energy management, which is essential for various applications including optical coherence tomography and chirped pulse amplification systems.
Innovation Solution
A ring optical circuit with beam diffraction compensation, dispersion, and amplification properties, where a broadband primary laser pulse undergoes multiple roundtrips with controlled energy loss and phase modulation by a chirped fiber Bragg grating, allowing for flexible pulse duration adjustment from 100 fs to 10 ns and independent energy control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a laser oscillator with fixed resonator parameters is used, then stable operation is ensured, but the pulse duration tuning range is limited
Solution Approach 1:
The patent applies dynamics by making the resonator length variable through an adjustable optical delay line. The resonator length can be dynamically changed to tune pulse duration from femtoseconds to nanoseconds while maintaining stable operation. The delay line uses a variable path length configuration that allows continuous adjustment without disrupting the mode-locking mechanism.
Solution Approach 2:
The patent achieves universality by designing a single laser oscillator that can operate across multiple pulse duration regimes (fs, ps, ns) by adjusting the resonator parameters. The same oscillator cavity supports different pulse durations through variable optical path length, eliminating the need for separate oscillators for different time scales.
2Duration of action of moving object
If spectral filtering is applied to reduce radiation bandwidth, then pulse duration can be extended, but coherence length increases
Solution Approach 1:
The patent uses dynamic control of the optical delay line to adjust the effective bandwidth-filtering interaction. By varying the delay time, the system can extend pulse duration without permanently narrowing the spectral bandwidth, thus maintaining low coherence length while achieving variable pulse durations.
Solution Approach 2:
The patent employs periodic modulation of the optical path length within the resonator to achieve pulse duration extension. The periodic variation in delay time allows the pulse to accumulate duration through multiple passes while the spectral bandwidth remains preserved, preventing coherence length increase.
3Adaptability or versatility
If the resonator length is varied to change pulse duration, then pulse duration tuning is achieved, but pulse repetition rate and energy change
Solution Approach 1:
The patent implements feedback control through an adjustable optical delay line that compensates for changes in pulse energy and repetition rate. By monitoring the resonator round-trip time and adjusting the delay accordingly, the system maintains stable pulse energy and repetition rate independent of the selected pulse duration setting.
Solution Approach 2:
The patent changes multiple resonator parameters simultaneously - optical path length, delay time, and gain distribution - to achieve pulse duration tuning while keeping pulse energy and repetition rate constant. The coordinated adjustment of these parameters allows independent control of pulse duration without affecting other critical parameters.
4Adaptability or versatility
If fiber sections of different lengths are inserted to tune pulse duration, then duration variation is possible, but mode-locking repeatability deteriorates
Solution Approach 1:
The patent replaces mechanical insertion of fiber sections with an optical delay line that uses variable path length configuration. This substitution eliminates mechanical disturbances to the mode-locking mechanism while achieving the same pulse duration tuning effect through optical path adjustment, thereby maintaining mode-locking repeatability.
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 approach enables a universal, stable, and easily controllable laser system capable of producing pulses with durations from 100 fs to 10 ns, maintaining low coherence length and high flexibility for diverse applications, including optical coherence tomography and chirped pulse amplification systems, without the limitations of existing technologies.
Implementation Method 1
interacting said part of the pulse with a dispersive optical element to form a chirped pulse
Implementation Method 2
phase modulation by a chirped fiber Bragg grating
Implementation Method 3
amplifying said chirped pulse to form an amplified chirped pulse
Implementation Method 4
laser beam diffraction compensation
Data Source
Figure 1~2
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Figure 5~6
AI summary
This invention relates to methods and devices for controlling a chirp and duration of a laser radiation pulse. At the same time, pulse energy is also controlled. The device of the present invention includes a ring optical circuit featuring laser beam diffraction compensation, dispersion and amplification. The ultrashort input pulse makes a predetermined number of roundtrips. During each roundtrip of the ring optical circuit, an amplified phase-modulated (chirped) pulse is formed, part of which is outcoupled as an output pulse. A sequence of output pulses of different durations is formed. One output pulse of the required duration is extracted from said sequence of output pulses with the help of an optical switch. Since the energy of the pulse is restored or increased at each roundtrip of the ring optical circuit, the number of roundtrips is unlimited. Duration of the pulses is varied within a wide range of values from several hundred femtoseconds to several tens of nanoseconds, preserving a coherence length not larger than 300 µm. The device of the present invention can be used as a very compact, purely electronically controlled and with flexible parameters pulse stretcher in a chirped pulse amplification system.