Abstract: A method for electric field measurement based on a levitated particle includes steps of (1) capturing a particle and levitating the captured particle; (2) adjusting a quantity of electric charge carried by the levitated particle; (3) measuring a charge number N of the levitated particle; (4) disposing the levitated particle in an electric field to be measured, measuring a displacement power spectral density Svxel of the levitated particle under the electric field and obtaining an electric field force Fel; and (5) according to a formula of E=Fel/Nqe, obtaining an electric field intensity E. An apparatus for electric field measurement based on a levitated particle includes a high-voltage DC (direct current) power supply, two bare wire electrodes, a vacuum chamber, a trapping laser, an objective lens, a pair of parallel electrodes, a collective lens, a quadrant photodetector, a lock-in amplifier, a signal generator and a power amplifier.

Abstract: The present application discloses a nanoparticle recognition device and method based on detection of scattered light with electric dipole rotation. According to the scattering model of nanoparticles, the in situ detection of particle morphology in an optical trap is realized by the methods of particle suspension control and scattered light detection and separation. Specifically, two linearly polarized laser beams are used, wherein the first laser beam suspends nanoparticles and rotates nanoparticles by adjusting the polarization direction; the polarization direction of the second linearly polarized light is unchanged, and scattered light in a specific dipole direction is excited; the change of the polarizability of the nanoparticles is deduced by monitoring the change of the light intensity of the scattered light excited by the second laser beam at the fixed position, so that particle morphology recognition is realized.

Abstract: An absolute gravimeter and a measurement method based on vacuum optical tweezers. The micro-nano particle releasing device is equipped with micro-nano particles, and is located above laser optical tweezers, and the laser optical tweezers have two capturing beams which pass through the respective convergent lenses and then converge at an intersection. An area where the intersection is located serves as an optical trap capturing region, and the micro-nano particles are stably captured by the two capturing beams in the optical trap capturing region. The optical interferometer is electrically connected to the signal processing device, the optical interferometer measures a displacement of the micro-nano particles in real time at the beginning of a free fall process from the optical trap capturing region and sends the displacement signal to the signal processing device. The signal processing device obtains a measured value of an absolute gravitational acceleration.

Abstract: A probe-based bidirectional electrophoretic force optical trap loading method includes steps of (1) detaching target particles from an upper electrode plate and capturing the target particles by a micro-scale probe based on a bidirectional electrophoretic force; (2) moving the probe with the target particles over an optical trap, applying a reverse electric field between the probe and the upper substrate electrode plate which is applied during a polar relaxation time of the target particles, and desorbing the target particles from the probe; and (3) turning on the optical trap, applying an electric field between the lower electrode plate and the upper electrode plate, adjusting the speed of the desorbed target particles through the electric field at which the optical trap is able to capture the desorbed target particles and the desorbed target particles moving to the effective capture range of the optical trap.

Abstract: A method for electric field measurement based on a levitated particle includes steps of (1) capturing a particle and levitating the captured particle; (2) adjusting a quantity of electric charge carried by the levitated particle; (3) measuring a charge number N of the levitated particle; (4) disposing the levitated particle in an electric field to be measured, measuring a displacement power spectral density Svxel of the levitated particle under the electric field and obtaining an electric field force Fel; and (5) according to a formula of E=Fel/Nqe, obtaining an electric field intensity E. An apparatus for electric field measurement based on a levitated particle includes a high-voltage DC (direct current) power supply, two bare wire electrodes, a vacuum chamber, a trapping laser, an objective lens, a pair of parallel electrodes, a collective lens, a quadrant photodetector, a lock-in amplifier, a signal generator and a power amplifier.

Abstract: A method for enhancing vacuum tolerance of optical levitation particles includes steps of: (1) turning on a trapping laser to form an optical trap, loading the particles to an effective capture region of the optical trap, and collecting scattered light signals; (2) turning on the preheating laser, and directing a preheating laser beam to the captured particles; (3) adjusting a power of the preheating laser until a particle heating rate is larger than a heat dissipation rate; (4) turning on the vacuum pump, and stopping evacuating when a vacuum degree is greater than a vacuum inflection point of a first reduction of the effective capture region of the optical trap; and (5) turning off the preheating laser when the scattered light signals collected by the photodetector no longer changes. The present invention improves a stable capture probability of the particles in high vacuum environment.

Abstract: A method for enhancing vacuum tolerance of optical levitation particles includes steps of: (1) turning on a trapping laser to form an optical trap, loading the particles to an effective capture region of the optical trap, and collecting scattered light signals; (2) turning on the preheating laser, and directing a preheating laser beam to the captured particles; (3) adjusting a power of the preheating laser until a particle heating rate is larger than a heat dissipation rate; (4) turning on the vacuum pump, and stopping evacuating when a vacuum degree is greater than a vacuum inflection point of a first reduction of the effective capture region of the optical trap; and (5) turning off the preheating laser when the scattered light signals collected by the photodetector no longer changes. The present invention improves a stable capture probability of the particles in high vacuum environment.

Abstract: A probe-based bidirectional electrophoretic force optical trap loading method includes steps of (1) detaching target particles from an upper electrode plate and capturing the target particles by a micro-scale probe based on a bidirectional electrophoretic force; (2) moving the probe with the target particles over an optical trap, applying a reverse electric field between the probe and the upper substrate electrode plate which is applied during a polar relaxation time of the target particles, and desorbing the target particles from the probe; and (3) turning on the optical trap, applying an electric field between the lower electrode plate and the upper electrode plate, adjusting the speed of the desorbed target particles through the electric field at which the optical trap is able to capture the desorbed target particles and the desorbed target particles moving to the effective capture range of the optical trap.

Abstract: Disclosed is an optical trap calibration apparatus and method based on variation of electric field by optical imaging of a nanoparticle. By means of a direct optical imaging method, a linear nanoparticle equilibrium position displacement under the action of a constant electric field is measured to realize calibration, thereby avoiding the introduction of error signals, and improving the reliability of differential calibration. The specific calibration method and apparatus of the present invention are not only suitable for calibration of electric field quantity, but also suitable for the calibration of other magnetic forces and the like. By means of the accurate calibration of mechanical quantity in the present invention, the development and application of the vacuum optical trap sensing technology can be promoted.

Abstract: Disclosed is a multi-dimensional optical tweezers calibration device based on electric field quantity calibration and a method thereof. The polarization-dependent characteristics of a tightly focused optical trap are utilized to realize triaxial electric field force calibration of particles through a one-dimensional electric field quantity calibration device. The method of the present application enables a particle electric field force calibration system to be compatible with particle delivery and particle detection systems; the device is simplified and calibration complexity is reduced.

Abstract: The present application discloses a nanoparticle recognition device and method based on detection of scattered light with electric dipole rotation. According to the scattering model of nanoparticles, the in situ detection of particle morphology in an optical trap is realized by the methods of particle suspension control and scattered light detection and separation. Specifically, two linearly polarized laser beams are used, wherein the first laser beam suspends nanoparticles and rotates nanoparticles by adjusting the polarization direction; the polarization direction of the second linearly polarized light is unchanged, and scattered light in a specific dipole direction is excited; the change of the polarizability of the nanoparticles is deduced by monitoring the change of the light intensity of the scattered light excited by the second laser beam at the fixed position, so that particle morphology recognition is realized.

Abstract: A method and a device for measuring light field distribution are provided; including steps of utilizing the optical trap to stably levitating particles, moving the optical trap to bring the particles close to the light field to be measured, and utilizing the photodetector to collect the scattered light signals of the particles at different positions in the three-dimensional space of the light field to be measured, and calculating the light field distribution of the light field to be measured according to the scattered light intensity which is proportional to the light intensity at that position. The device for measuring the optical field distribution includes a laser, an optical trapping path, particles, a photodetector, a control system and an upper computer; the laser emits a laser, passes through the optical trapping path, and emits highly focused captured light B to form an V optical trap to capture particles.

Abstract: A method and a device for measuring light field distribution are provided; including steps of utilizing the optical trap to stably levitating particles, moving the optical trap to bring the particles close to the light field to be measured, and utilizing the photodetector to collect the scattered light signals of the particles at different positions in the three-dimensional space of the light field to be measured, and calculating the light field distribution of the light field to be measured according to the scattered light intensity which is proportional to the light intensity at that position. The device for measuring the optical field distribution includes a laser, an optical trapping path, particles, a photodetector, a control system and an upper computer; the laser emits a laser, passes through the optical trapping path, and emits highly focused captured light B to form an V optical trap to capture particles.