Pulsed Laser Pulse Blanking via Polarization Rotation
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Solution Overview
Problem
In optically pumped solid-state pulse lasers used for MALDI, interrupting the sequence of laser pulses leads to an increase in energy density of subsequent pulses, causing instability in mass resolution and ion yield, especially at high pulse frequencies, and existing solutions are either complex or costly.
Innovation Solution
A rapidly switchable polarization rotator, comprising a Pockels cell and λ/4 wave plate, is used to rotate the polarization plane of laser light, allowing for the interruption of laser pulses without increasing energy density, by using a polarization filter to absorb and destroy the rotated light, maintaining constant energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If laser pulses are interrupted at high pulse sequence frequencies, then the ability to realign targets on sample support is improved, but the energy density of subsequent pulses increases due to continued pumping
Solution Approach 1:
The polarization rotator is switched to the blanking position before the laser pulse is generated, preventing the buildup of population inversion during the blanking period. This preliminary action ensures that when pulsing resumes, the energy density returns to normal levels without multiplication effects.
Solution Approach 2:
The polarization rotator acts as an intermediary element that controls the polarization state of the laser beam. By rotating the polarization plane, it enables or disables the laser output without affecting the pump diode operation, thus mediating between the need for pulse interruption and energy density stability.
2Stability of the object's composition
If the pumping process is controlled to prevent energy increase, then the energy density constancy is improved, but the service life and efficiency of the pump diode deteriorates at high pulse frequencies
Solution Approach 1:
The solution extracts the control function from the pumping system and places it in the optical path via the polarization rotator. This allows pulse blanking to be achieved independently of the pump diode control, preventing damage to the pump diode while maintaining energy density constancy.
3Adaptability or versatility
If mechanical arrangements or electro-optical methods are used to blank out pulses, then the pulse interruption capability is improved, but the device complexity and cost increase
Solution Approach 1:
The polarization rotator serves multiple functions: it enables pulse blanking, controls laser output, and maintains energy density stability. This multi-functionality eliminates the need for separate mechanical blanking devices or complex electro-optical systems, reducing overall device complexity.
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 method enables low-cost, non-complex blanking of laser pulses, maintaining energy constancy and extending the service life of the pump diode, even at high pulse frequencies, thereby improving mass resolution and ion yield stability.
Implementation Method 1
A rapidly switchable polarization rotator, comprising a Pockels cell and λ/4 wave plate, is used to rotate the polarization plane of laser light
Implementation Method 2
A rapidly switchable polarization rotator, comprising a Pockels cell and λ/4 wave plate, is used to rotate the polarization plane of laser light
Implementation Method 3
allowing for the interruption of laser pulses without increasing energy density, by using a polarization filter to absorb and destroy the rotated light
Data Source
AI summary
The invention relates to optically pumped and pulsed solid-state lasers which are used in mass spectrometers in particular for ionization by matrix-assisted laser desorption (MALDI) and which operate at pulse frequencies of up to 10 kilohertz or even higher. The invention proposes that, instead of interrupting the clocked sequence of the laser operation, individual light pulses or groups of light pulses are blanked out so that subsequent light pulses do not have a higher energy density, in accordance with the requirements for LDI processes. Methods and devices for the blanking out of light pulses are provided which are, in particular, low cost and considerably less complex than other methods.