Optical trap using a focused hollow beam of unequal axisymmetry and no angular momentum for trapping and rotating airborne particles
Inventors
Arnold, Jessica A. • Kalume, Aimable • Pan, Yongle • Videen, Gorden
Assignees
United States Department of the Army
Publication Number
US-12276593-B2
Publication Date
2025-04-15
Expiration Date
2042-03-14
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
Systems and methods for trapping and holding airborne particles using an orienting hollow beam are disclosed. In the various embodiments, an optical trap comprises: a light source for generating a beam of light; optics and/or mechanics for forming and shaping the beam of light into an orienting hollow beam having unequal axisymmetry with a substantially hollow ring geometry cross-section and no angular momentum; an optical focusing element for focusing the orienting hollow beam; and a trapping region where an airborne particle can be present to be trapped and held at or near a focal point of the focused optical focusing element. In this arrangement, the particle is trapped at or near the focal point of the focused orienting hollow beam. In this arrangement, the particle is trapped at or near the focal point of the focused orienting hollow beam. The orienting hollow beam may be made rotatable in some embodiments.
Core Innovation
Embodiments of the present invention disclose systems and methods for trapping and holding airborne particles using an orienting hollow beam. The optical trap comprises a light source for generating a beam of light, optics and/or mechanics for forming and shaping the beam into an orienting hollow beam with unequal axisymmetry, a substantially hollow ring geometry cross-section, and no angular momentum, an optical focusing element for focusing the orienting hollow beam, and a trapping region where an airborne particle can be trapped and held at or near the focal point of the focused beam. The orienting hollow beam may be rotatable in some embodiments.
The problem being solved arises from the existing limitations in optical trapping and measuring small airborne particles. Due to the complex shapes, varied sizes, and compositional inhomogeneity of aerosols, characterization requires techniques that consider particle orientation relative to the light source and detectors. Measurements based on light scattering are limited because scattering signals depend on aerosol orientation. Existing particle manipulation apparatuses mostly induce combined angular momentum resulting in periodic circular motion, with rotational periodicity dependent on fixed properties of the particle and beam configuration, which limits control over orientation and rotation speed. Improvements are desired to allow controlled rotation and orientation of trapped airborne particles for better measurement and analysis.
The invention addresses these issues by providing an optical trap that uses an orienting hollow beam with unequal axisymmetry and no angular momentum, enabling trapping, holding, and controlled manipulation of airborne particles' orientations. The beam can be rotated to apply controlled torque, enabling precise rotation or orientation holding of trapped particles. This allows for imaging and measurement of particles at multiple orientations, increasing the utility for analytical techniques such as Raman spectroscopy. The apparatus may include rotation means implemented through mechanical rotation stages or programmed spatial light modulators, providing controlled angular speed and direction, and the ability to pause rotation at any angular orientation.
Claims Coverage
The patent includes multiple independent claims covering two main categories of optical traps and methods for trapping and rotating airborne particles.
Optical trap using a spatial light modulator and computer-generated hologram to create and rotate an orienting hollow beam
An optical trap comprising a light source, a spatial light modulator (SLM) configured to generate a computer-generated hologram (CGH) of an orienting hollow beam with unequal axisymmetry and no angular momentum, an optical focusing element to focus the beam to a single focal point, a trapping region for airborne particles, and an imaging and/or measuring system. The SLM is programmed to rotate the CGH or is mounted on a rotating stage to rotate the beam about a fixed axis, thereby rotating the trapped particle.
Optics and/or mechanics for forming and shaping the light beam and providing controlled rotation
Optics and/or mechanics can include means for forming and shaping an intermediate beam from the beam of light, and the CGH forms the orienting hollow beam from the intermediate beam. The intermediate beam may be a cylindrical hollow beam and the orienting hollow beam an elliptical hollow beam. The first means can include holography, SLMs, phase and amplitude masks, biaxial crystals, diffraction patterns, aberrations, interference patterns, or a pair of axicon lenses. The CGH and rotating stage allow controlled angular speeds of rotation, including starting, stopping, speed changes, pausing at a given orientation, and reversing direction of rotation.
Optical trap using cylindrical lens and rotation stage to form and rotate elliptical hollow beam
An optical trap comprising a light source, optics for shaping and forming a circular hollow beam, a cylindrical lens (with focal length 5000 mm or longer) for deforming the circular hollow beam into an elliptical hollow beam, a rotation stage supporting and rotating the cylindrical lens in a controlled manner, an optical focusing element for focusing the elliptical hollow beam into a hollow elliptical cone, and a trapping region to trap particles near the focal point. The rotation of the cylindrical lens controls the rotation of the elliptical hollow beam and thus the trapped particle.
The claims cover inventive features related to generating orienting hollow beams with unequal axisymmetry and no angular momentum using spatial light modulators and mechanical optics, methods for rotating these beams to control particle orientation, and configurations involving cylindrical lenses and rotation stages to form and rotate elliptical hollow beams. These features enable trapping, holding, and controlled rotation of airborne particles for precise measurement and imaging.
Stated Advantages
Allows controlled rotation of trapped airborne particles at variable speed and direction, including pausing at any desired angular orientation.
Enables trapping and holding of airborne particles at low numerical aperture due to the use of hollow beams with reduced scattering forces.
Improves measurement and characterization of particles by enabling multi-orientation imaging and analysis, such as Raman spectroscopy and elastic light scattering.
Supports both absorbing and non-absorbing particles in air, enabling real-time airborne aerosol detection and characterization.
Integrates easily with various analytical tools due to the use of a single focused beam and low NA focusing optics, enhancing system versatility.
Documented Applications
In-vitro inspection and measurement of airborne particles in laboratory settings.
Real-time detection and identification of biological or chemical aerosols.
Measurement of particle properties including shape, size, internal structure, refractive index, absorption, molecular composition, and chemical reactions.
Imaging and analysis of airborne particles at multiple controlled orientations for detailed characterization.
Continuous sampling systems for airborne particles including trapping, measuring, releasing, and sorting particles based on measured properties.
Interested in licensing this patent?