DMD Laser Beam Shaping with Dispersion Compensation
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Solution Overview
Problem
Current laser beam shaping technologies, such as those using spatial light modulators and deformable mirrors, are limited by their shaping rate and resolution, particularly when dealing with ultrafast pulsed lasers, which are essential for advanced scientific and industrial applications like two-photon excited microscopy and micro machining.
Innovation Solution
A device comprising a digital micromirror device (DMD) and a dispersion compensation unit, which includes a diffraction component and lenses, is used to shape and scan ultrafast laser beams, enabling higher shaping and scanning rates and resolutions by neutralizing angular dispersion, allowing for arbitrary beam profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a digital micromirror device (DMD) is used to shape ultrafast laser beams, then the shaping rate and resolution are improved, but angular dispersion is introduced that limits the effectiveness for pulsed lasers
Solution Approach 1:
The dispersion compensation unit is configured to pre-compensate for the angular dispersion introduced by the DMD. By placing the compensation unit in the optical path before or after the DMD, the system counteracts the dispersion effect in advance, allowing the DMD to operate at high speeds without compromising beam shaping precision for ultrafast pulsed lasers
Solution Approach 2:
A dispersion compensation unit is introduced as an intermediary component between the laser source and the DMD. This unit includes optical elements that generate equal but opposite angular dispersion to cancel out the DMD-induced dispersion, enabling high-speed shaping of ultrafast pulses without the harmful dispersion effects
2Productivity
If conventional beam shaping methods using SLM or DM are used, then beam shaping is achieved, but the shaping rate is limited to below 100 Hz or 10,000 pixels resolution
Solution Approach 1:
The patent replaces conventional mechanical beam shaping systems (SLM with liquid crystal modulation or DM with physical deformation) with a DMD-based system. The DMD uses binary micromirror arrays that can be electronically controlled at much higher speeds (up to 32 kHz), substituting the slow mechanical/optical modulation mechanisms with faster electronic switching while maintaining high resolution through the large number of controllable micromirrors
3Adaptability or versatility
If DMD is used for CW laser shaping, then high pattern rate and resolution are achieved, but extension to ultrafast pulsed lasers is limited due to dispersion complexity
Solution Approach 1:
The patent addresses the transition from CW to ultrafast pulsed laser operation by introducing dispersion compensation that specifically targets the broadband spectral characteristics of ultrafast pulses. The compensation unit is designed to handle the wide spectral bandwidth of femtosecond lasers, adjusting the dispersion parameters to match the pulse duration and spectral width, thereby enabling DMD operation with ultrafast pulses without excessive 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
The solution provides high-speed, high-resolution beam shaping and scanning capabilities, overcoming the limitations of existing technologies by enabling precise control over pulsed laser beams, facilitating diverse applications including ultrafast z-scanning, random-access scanning, and omnidirectional imaging.
Implementation Method 1
the diffraction component is a component that disperses light, such as a grating, a prism, a hologram and another DMD
Implementation Method 2
a lens pair, configured to collimate and expand the pulsed laser beam and image the beam onto the DMD
Data Source
AI summary
A device and method are for shaping and scanning an ultrafast laser beam. The device includes a laser source configured to output a pulsed laser beam containing different frequency spectrum, a digital micromirror device (DMD) consisting of micromirrors, which are configured to receive the laser beam and shape the received laser beam with computer generated holograms, and a dispersion compensation unit, arranged before or after the DMD, which is configured to transfer the laser beam from the laser source to the DMD with a designated angular dispersion for neutralizing the first angular dispersion introduced by the DMD.