CN102928909B - A kind of phase delay device based on surface phasmon - Google Patents

Abstract

The present invention discloses a phase retarder based on surface plasmon polaritons. Most of the existing inventions and researches on optical phase modulators are based on traditional optical devices such as birefringent crystals and liquid crystals. These designs are only applicable to larger scales. Optical devices are not conducive to integration. The invention utilizes the surface plasmon properties of metals to shrink the phase retarder to the nanometer level, and can effectively achieve phase retardation for light of a specific wavelength by changing the size structure of the nanoparticles. This structure can be applied to various optical detection compact instruments.

Description

A phase retarder based on surface plasmons

technical field

The invention belongs to the field of optoelectronic technology, and relates to a noble metal nanostructure, in particular to a phase retarder based on surface plasmons.

Background technique

In the field of optical components, a phase retarder can produce an additional optical path difference for light with a specific polarization direction. The most common phase retarder is the wave plate. The basic principle used by the wave plate is the birefringence property of the material, that is, the refractive index of the material is different for light in different directions. Among them, the half-wave plate can change the polarization direction of linearly polarized light, and the quarter-wave plate can convert linearly polarized light into circularly polarized light. In addition, liquid crystal phase modulators can achieve adjustable phase changes. This series of basic components has been widely used in various optical precision instruments for spectrum, optical detection and other fields.

After searching the literature for traditional optical phase modulators, it is found that the smallest phase retardation wave plate can be as thin as hundreds of microns in size. With the rapid progress of integrated optics and modern precision processing technology, the scale of on-chip integrated optical devices has also been continuously miniaturized, reaching the nanometer scale. At this level, due to the limitations of the birefringence properties of the material itself and the size of the refractive index, the above-mentioned related design principles can no longer be realized, so no effective nanoscale phase delay elements have been manufactured yet.

Contents of the invention

The purpose of the present invention is to address the shortcomings of the above-mentioned existing concepts and technologies, and propose a phase retarder based on surface plasmons by utilizing the optical properties of metal nanostructures.

The technical scheme that the present invention solves its technical problem adopts is as follows:

The invention includes transparent substrates as well as metal nanoparticles.

The transparent substrate is mainly used to support metal nanoparticles, isotropic and low-dispersion optical glass is used, and does not modulate incident light.

The metal nanoparticles play a major role in modulating the incident light, and the shapes of the metal nanoparticles can be various, including disk, spherical, rod, and triangle; every three metal nanoparticles are a group, and each group of metal nanoparticles The shape is one of them or a combined structure composed of several of them, the distance between each group of metal nanoparticles is greater than 100 nanometers, and multiple groups of metal nanoparticles are distributed in a periodic array. Usually metal nanostructures are designed as disk structures. From the perspective of integrated optics and processing technology, disk structures can be realized by masking, etching, evaporation or sputtering.

The size of the metal nanoparticles is sub-wavelength level, the size is: 50 nanometers in diameter, 10 nanometers in thickness, and the distance between particles in each group of metal nanoparticles is 15 nanometers. The size and structure of metal nanoparticles mainly affect the magnitude of the phase modulation for incident light.

The beneficial effects that the present invention has are:

The invention utilizes the optical properties of metal nanoparticles, and compared with the existing components, the volume is greatly reduced (tens of nanometers to hundreds of nanometers in thickness), and the phase modulation can be completed on the material interface, which can be considered as a two-dimensional phase delay device. Such a structure is easy for large-scale optical integration and can be used as an important component of optical detection instruments.

Description of drawings

Fig. 1 is a schematic diagram of the overall structure of the present invention;

Fig. 2 is the unit schematic diagram of each group of metal nanoparticles of the present invention;

Fig. 3 is the phase delay spectrum of the present invention.

Detailed ways

The specific implementation of the present invention will be described in detail below in conjunction with the accompanying drawings: the case of this implementation is based on the phase retarder based on surface plasmons proposed by the present invention, but the scope of protection of the present invention is not limited to the following implementation and case.

As shown in FIG. 1 , a phase retarder based on surface plasmons includes a transparent substrate 1 and metal nanoparticles.

The transparent substrate is mainly used to support metal nanoparticles, isotropic and low-dispersion optical glass is used, and does not modulate incident light.

The metal nanoparticles play a major role in modulating the incident light, and the shapes of the metal nanoparticles can be various, including disk, spherical, rod, and triangle; every three metal nanoparticles are a group, and each group of metal nanoparticles The shape is one of them or a combined structure composed of several of them, the distance between each group of metal nanoparticles is greater than 100 nanometers, and multiple groups of metal nanoparticles are distributed in a periodic array. In the figure, the metal nanostructure is designed as a disk-shaped structure. From the perspective of integrated optics and processing technology, the disc structure can be realized by masking, etching, evaporation or sputtering.

As shown in Figure 2, in each group of metal nanoparticles, the shape of the metal nanoparticles is disk, and the materials are gold and silver, both of which have strong plasmon resonance effects in the visible band. Through the coupling effect of the two material particles, a phase-modulated window can be formed on the spectrum to achieve a specific phase delay function. By substituting the material of the metal nanoparticles, phase modulation can also be selectively performed for light in a certain wavelength range. The size of the metal nanoparticles shown in FIG. 2 is: 50 nanometers in diameter, 10 nanometers in thickness, and the particle-to-particle side spacing in each group of metal nanoparticles is 15 nanometers. The size and structure of metal nanoparticles mainly affect the size of the phase modulated by the incident light. The structure designed in the figure can realize the phase difference caused by the two orthogonal polarizations for the target wavelength. In addition, the material of the metal nanoparticle 2-2 in the middle of the figure is gold, and the material of the metal nanoparticle 2-2 on both sides is silver. The polarized light component 3 and the polarized light component 4 are orthogonal to each other, and are incident on the metal nanoparticles, and then plasmon resonance occurs when interacting with the metal nanoparticles, producing different phase delays for the polarized light components 3 and 4.

As shown in Fig. 3, it is a phase modulation characteristic under a specific structure size. In the short wavelength range (<500nm), the structure is essentially transparent to light. In the long wavelength range (590-650nm), the phase retardation of the nanostructures to the incident light reaches , and form a wide-band window, which can realize the function of a traditional quarter-wave plate, and can convert linearly polarized light and circularly polarized light into each other. The size of the metal nanoparticles is sub-wavelength.

The phase delay function of the phase retarder is determined by the metal nanostructure on the substrate. In specific use, the required structure can be manufactured according to the requirement. The parameters that can be adjusted include: shape, quantity, size, material, spacing, etc. of nanoparticles. Therefore, the size of the phase difference, the window position, and the window width change accordingly. In this way, a phase retarder based on surface plasmons is realized.

Claims (1)

1., based on a phase delay device for surface phasmon, comprise transparent substrates and metal nanoparticle; It is characterized in that:

Described transparent substrates is mainly used in support metal nano particle, adopts isotropy and the optical glass of low dispersion;

Described metal nanoparticle plays main modulating action for incident light, and the shape of metal nanoparticle is bar-shaped; Every three metal nanoparticles are one group of the linear alignment, and intermetallic metal nano-particle material is gold, and both sides metal nanoparticle material is silver; Often the back gauge organized between metal nanoparticle is greater than 100 nanometers, and many group metal nanoparticles are cyclic array distribution;

Described metal nanoparticle is of a size of sub-wavelength level, and it is of a size of: diameter 50 nanometer, thickness 10 nanometer, often organizes limit spacing 15 nanometer of metal nanoparticle and metal nanoparticle in metal nanoparticle; The maximum phase that described phase delay device obtains postpones 1.5 π, linearly polarized light can be converted into circularly polarized light.