Pr-Doped Green Pulse Amplifier Without SHG Crystal Degradation
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Solution Overview
Problem
Existing methods for generating ultrafast green laser pulses with high energy and short duration are costly, complex, and result in degraded optical quality of SHG crystals, with direct amplification in the visible region being limited to the red region and unavailable in the green region, and previous methods elongate pulse durations beyond 30 ps.
Innovation Solution
A laser amplifier system using a praseodymium (Pr)-doped gain medium pumped by a gallium nitride (GaN)-based diode laser, which directly amplifies green seed pulses with a peak wavelength between 520 nm and 540 nm, achieving spectral bandwidths over 0.6 nm, and employs regenerative amplification with pulse compression to achieve pulse durations less than 30 ps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If second harmonic generation (SHG) is used to generate green laser pulses from 1-μm ultrafast pulses, then green laser pulses can be produced, but the optical quality of the SHG crystal becomes degraded over time and replacement causes additional maintenance cost
Solution Approach 1:
The patent extracts the green laser generation process from the SHG method and implements direct amplification of green seed pulses using Pr3+-doped gain media. This removes the SHG crystal from the system, eliminating the degradation and maintenance issues while achieving the desired green laser pulse output.
Solution Approach 2:
The patent replaces the expensive, degradable SHG crystal with a more robust Pr3+-doped gain medium that can be pumped by GaN-based diode lasers. This substitution uses materials that are more resistant to degradation and have lower maintenance costs.
2Use of energy by moving object
If higher pulse energies are used for the fundamental wavelength to generate high energy ultrashort pulses in green via nonlinear process, then green pulse energy increases, but the design complexity and engineering efforts for the near infrared laser increase, resulting in high initial cost
Solution Approach 1:
Instead of generating green pulses through SHG from 1-μm pulses (conventional approach), the patent inverts the approach by directly amplifying green seed pulses using Pr3+-doped gain media pumped by blue/violet GaN-based diode lasers. This eliminates the need for complex high-energy 1-μm laser design.
Solution Approach 2:
The patent changes the operating parameters by using GaN-based diode lasers with wavelengths between 435 nm and 450 nm to pump the Pr3+-doped gain medium, which directly emits green light. This parameter change simplifies the overall system design compared to the conventional 1-μm laser approach.
3Productivity
If direct amplification is used in near infrared optical pulses or UV region, then amplification can be achieved, but the wavelength of frequency-doubling from the green pulse is still shorter than 290 nm and multiple photon absorption of green pulse is still used for internal micro-machining
Solution Approach 1:
The patent optimizes the pulse duration parameter by using regenerative amplification and pulse compression techniques to achieve pulse durations less than 30 ps (preferably less than 10 ps, more preferably less than 1 ps). This parameter optimization enables internal micro-machining while maintaining the benefits of direct green pulse amplification.
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 system achieves ultrafast green laser pulses with energies 10 times greater than the seed pulse, spectral bandwidths of 0.6 nm, and pulse durations as short as 0.94 ps, providing efficient and cost-effective amplification suitable for precision machining of wide-bandgap semiconductors.
Implementation Method 1
A laser amplifier system using a praseodymium (Pr)-doped gain medium pumped by a gallium nitride (GaN)-based diode laser, which directly amplifies green seed pulses
Implementation Method 2
gallium nitride (GaN)-based diode laser
Implementation Method 3
employs regenerative amplification with pulse compression to achieve pulse durations less than 30 ps
Data Source
AI summary
A laser amplifier for a green laser pulse includes at least one gain medium doped with praseodymium and at least one gallium nitride based diode laser for pumping the gain medium. A green seed laser pulse going through the gain medium becomes an amplified green laser pulse.