Regenerative Amplifier Beam Axis Stabilization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current EUV light generation systems face challenges in achieving the high precision and power required for microfabrication at 32 nm or less, particularly in stabilizing the beam axis and amplifying pulsed laser beams with short pulse widths and high repetition rates for extreme ultraviolet light production.
Innovation Solution
A regenerative amplifier system is developed, incorporating a pair of resonator mirrors, a slab amplifier, and a multipass optical path, which includes concave high-reflection mirrors to stabilize the beam axis and efficiently amplify pulsed laser beams, using CO2-gas as a gain medium and Pockels cells for polarization control, allowing for the formation of a zigzag optical path that maintains beam stability and amplifies the laser to desired intensity and pulse width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-pass amplifier is used, then the device complexity is low, but the beam axis stability and amplification efficiency are insufficient for high-power EUV generation
Solution Approach 1:
The patent implements a nested optical configuration where a multipass amplifier is nested within a regenerative amplifier cavity. The multipass section with its folding mirrors and lenses is embedded inside the resonator formed by the regenerative amplifier mirrors, allowing the laser beam to undergo multiple amplification passes while maintaining beam axis stability through the nested structural arrangement.
Solution Approach 2:
The patent introduces a zigzag optical path using folding mirrors that change the spatial dimension of beam propagation. Instead of a simple linear pass through the amplifier, the beam is redirected multiple times through the gain medium in a zigzag pattern, increasing the effective interaction length and amplification efficiency without proportionally increasing the physical footprint of the device.
2Productivity
If the pulse width is shortened to achieve high repetition rates, then the productivity increases, but the amplification efficiency and beam stability deteriorate
Solution Approach 1:
The regenerative amplifier configuration enables continuous circulation of the laser pulse through the gain medium multiple times within the resonator cavity. This continuous action allows short pulses to be amplified repeatedly without losing beam stability, as the beam maintains its spatial coherence throughout multiple passes through the amplification medium.
Solution Approach 2:
The system employs periodic modulation of the Q-switch and Pockels cells to control the timing and duration of amplification cycles. By synchronizing the periodic switching of these components with the pulse circulation in the resonator, the system maintains stable beam axis control while achieving high repetition rates through rhythmic amplification cycles.
3Power
If the laser power is increased for high-power EUV generation, then the energy output increases, but the beam axis stability and pulse width control worsen
Solution Approach 1:
The patent employs dynamic control elements including Q-switches and Pockels cells that can be actively modulated during operation. These dynamic components allow real-time adjustment of the amplification process, enabling the system to maintain precise pulse width control even as the overall laser power increases through multiple passes in the regenerative amplifier.
Solution Approach 2:
The regenerative amplifier configuration provides inherent feedback as the laser beam circulates through the resonator cavity multiple times. This feedback mechanism allows the system to self-regulate the amplification process, maintaining stable pulse characteristics and beam axis control while building up high power through repeated passes through the gain medium.
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 effectively stabilizes the beam axis and amplifies pulsed laser beams to high power with short pulse widths and high repetition rates, enabling efficient EUV light generation suitable for advanced microfabrication applications.
Implementation Method 1
a slab amplifier provided between the pair of the resonator mirrors for amplifying a laser beam with a predetermined wavelength outputted from the laser device
Implementation Method 2
Pockels cells for polarization control
Implementation Method 3
concave high-reflection mirrors to stabilize the beam axis
Implementation Method 4
an optical system disposed to configure a multipass optical path along which the laser beam is reciprocated inside the slab amplifier, the optical system transferring an optical image of the laser beam at a first position as an optical image of the laser beam at a second position
Data Source
AI summary
A regenerative amplifier according to one aspect of this disclosure is used in combination with a laser device, and the regenerative amplifier may include: a pair of resonator mirrors constituting an optical resonator; a slab amplifier provided between the pair of the resonator mirrors for amplifying a laser beam with a predetermined wavelength outputted from the laser device; and an optical system disposed to configure a multipass optical path along which the laser beam is reciprocated inside the slab amplifier, the optical system transferring an optical image of the laser beam at a first position as an optical image of the laser beam at a second position.