Single Aspheric Lens Research Articles

Optical levitation in high vacuum using a 0.9-numerical-aperture lens

Nanoparticles levitated in high vacuum are isolated from the surrounding environment and thus can be used in various applications, including quantum physics research. We demonstrated optical levitation of a nanoparticle, which was trapped without cooling at a pressure of 4.5 × 10−3 Pa, using a single aspheric lens with a large numerical aperture (= 0.9) and 1030-nm laser. We also activated parametric feedback cooling to trap the particle at a pressure of 5.8 × 10−4 Pa. This experimental system will be useful for studying nanoparticles in ultrahigh vacuum and for building a mixed system with laser-cooled atoms.

Design of a single aspheric beam homogenizer for accurate particle sizing application.

Understanding, detection, and accurate monitoring of particles are of utmost importance in various industrial fields and environmental science. Optical sensors allow for real-time monitoring of particles at the single species level by analyzing the elastically scattered light intensities. Nevertheless, since most laser diodes employed for illuminating the particle generally follow a Gaussian-type intensity distribution, the non-uniform energy distribution across the aerosol channel causes considerable errors in the conversion of the scattered light intensities into the actual particle sizes. In order to achieve uniform illumination of particles across the aerosol channel and improve the particle sizing and classification accuracy, we design and customize a single aspheric lens, which efficiently converts the divergent Gaussian beam profile of a TO packaged laser diode into a one-dimensional flattop beam profile along the fast axis at the desired working distance. A beam uniformity better than 5% has been achieved. Furthermore, we demonstrate a practical sensing application using the designed lens for accurate particle sizing, and an obvious improvement in the accuracy has been achieved compared to that based on off-the-shelf aspheric lenses. The singlet beam homogenizer developed in this work has many appealing features (e.g., high uniformity and energy efficiency, compactness, and low stray light), which is especially relevant for building portable particle sensors in order to address various industrial applications where on-site or remote metrology and classification of particles are required.

High-resolution imaging of Rydberg atoms in optical lattices using an aspheric-lens objective in vacuum.

We present a high-resolution, simple, and versatile system for imaging ultracold Rydberg atoms in optical lattices. The imaging objective is a single aspheric lens [with a working distance of 20.6 mm and a numerical aperture (NA) of 0.51] placed inside the vacuum chamber. Adopting a large-working-distance lens leaves room for electrodes and electrostatic shields to control electric fields around Rydberg atoms. With this setup, we achieve a Rayleigh resolution of 1.10 μm or 1.41λ (λ = 780 nm), limited by the NA of the aspheric lens. For systems of highly excited Rydberg states with blockade radii greater than a few μm, the resolution achieved is sufficient for studying many physical processes of interest.

An optimization method of dynamic patterns based on aspheric microlens array

An optimization method is proposed to improve the image quality of dynamic patterns in this paper. In order to obtain parallel emergent beam of high quality, aspheric microlens array is used in the optical system. Besides, an analytical model of the substrate and a single aspheric lens of MLA is presented based on the principle of ray tracing which is used in optical design for virtually tracing rays through an optical system. Moreover, how do the parameters influence the image quality is analyzed and the relationship between the conic constant and the divergence angle of emergent beam is derived. Preliminary optimization results with a second order aspheric lens are compared with the simulation results obtained by ZEMAX. The ray tracing method in this article helps improve the image quality of dynamic patterns and has the potential to be used in designing aspheric surface because it offers a way to improve the parallel rays and optimize the parameters of the optical system.

Aberration correction of a single aspheric lens with particle swarm algorithm

In order to design a single aspheric lens to meet the requirements of spherical aberration, the particle swarm algorithm is applied to the aberration correction for a single aspheric lens. A mathematical model is constructed, and a program code is developed. Merit functions in an optical system are employed as fitness functions, which combined coefficients of a higher order polynomial equation, a reciprocal of radius of curvature, the conic constant, thicknesses among lens surfaces and refractive indices regarding an optical system. By using this function, the automatic correction of spherical aberration is carried out. The example for a single aspheric lens design using particle swarm algorithm shows that PSO as a tool of the spherical aberration correction for a single aspheric lens is simple and effective, and easy to find a series of good design results. The asphere's more complex surface profile can reduce or eliminate easily spherical aberration at different incidence heights at one time. The automatic design and analysis of a single aspheric lens using this method from the view of a particular optical design problem are presented.

2P9-1 Precision measurement of convergence characteristic of single aspheric acoustic lens(Poster Session)

2P9-1 Precision measurement of convergence characteristic of single aspheric acoustic lens(Poster Session)

A simple bi-convex refractive laser beam shaper

This paper describes a novel bi-convex single aspheric lens that converts a spatially non-uniform laser beam into one with a uniform intensity distribution. The basis for this new lens is derived theoretically and lens performance is evaluated using detailed simulation under different conditions. This new design leads to a simple single-aspheric-lens configuration that substantially reduces fabrication difficulty. A method for compensating profile distortion induced by non-ideal factors is introduced. In addition, the limitations for practical applications are also discussed.

Confocal reader for biochip screening and fluorescence microscopy

We developed a fluorescence reader for the sensitive detection of surface-generated fluorescence. The system is applicable for high resolution imaging as well as for the readout of large biochips. The surface of a microscope coverslip is scanned with a laser beam focused to a waist diameter of 500 nm (FWHM) by means of a single aspheric lens. Scanning large areas with a focused beam usually evokes the need of automatic control elements to adjust the laser spot to the designated position at the surface. Due to the special design of the reader, the focus keeps at the plane of the surface even when scanning large areas, obviating the requirement of any real time control. Thus the instrument is straightforward and inexpensive. Nevertheless it features a high sensitivity and high optical resolution. The versatility of the instrument is demonstrated by imaging cells and reading out a DNA-chip. The excellent sensitivity is shown by detecting single fluorescently labeled antibodies.

The Analysis Of The Form Of Aspheric Lens Surfaces

Recent developments in high precision machining have allowed for the design and manufacture of precision aspheric lenses. These have the advantage over conventional spherical lenses in that a multiple element lens can be replaced by a single aspheric lens. There are however difficulties both in the measurement of the lens surface after machining and the assessment of the quality of the lens. In this paper an aspheric lens surface is measured using a 3D Form Talysurf. The data are then analysed using an analytical least-squares technique to fit the points to an exponential function. The methods developed show that the machining methods can now be complemented by an analysis technique.

Achromatic and sharp real imaging of a point by a single aspheric lens

By a single lens (two refracting surfaces, one dispersive medium) an achromatic real point image can be obtained. We show how such a lens brings a large aperture bundle of axial-parallel rays to the same sharp focus for two wavelengths, that is, for two refractive-index values. The normal of one of the two refracting surfaces is, in general, discontinuous at the axis. The numerical aperture which is practically attainable can be enhanced by off-axis steps in the refracting surfaces. The design principles for such lenses, computational formulas, and examples of results are given. Limitations and further possibilities are discussed.