CN103605247B - Double-layer cascade connection optical limiter - Google Patents

Abstract

A multi-layer cascaded optical limiter is composed of a dimethylformamide dispersion of single-walled carbon nanotubes and a double-layer hollow transparent container carried by a dimethylformamide solution of zinc phthalocyanine. The adjustment of the optical limiting curve can be realized by adjusting the order and concentration of the nonlinear medium. The invention can be applied in the field of laser protection to protect the human body or sensors from strong light damage.

Description

Double layer cascaded optical limiter

technical field

The invention relates to an optical limiter, in particular to a double-layer cascaded optical limiter

Background technique

Due to its high intensity, coherence, collimation and other advantages, laser is playing an increasingly important role in the fields of manufacturing, medicine, science and technology, and safety. However, laser is also a dangerous light source, which has a devastating effect on sensitive optical devices, human eyes, skin, etc. Therefore, how to enhance the safety of laser use has become a hot spot of concern. In order to effectively control the energy density of laser projection, the concept of an optical limiter has been proposed, which has the characteristics of low optical transmittance at high optical energy density and high transmittance at low optical energy density. This device allows light beams below a preset light intensity to pass through, but when the light intensity is higher than the preset light limiting device will block the passage of the light beam, thereby preventing subsequent target objects from being damaged by excessively high-energy laser light. Optical limiting devices can be used for the protection of optical sensors, the safety protection of human eyes in laser laboratories, etc., and have broad application prospects.

In recent years, people have made a lot of efforts in finding materials with strong nonlinear response and wide response spectrum in order to make practical optical limiters. At present, nonlinear optical materials used in optical limiters can be roughly divided into nonlinear scattering (NLS) and reverse saturable absorption (RSA) according to the nonlinear extinction mechanism. The former, such as carbon nanotubes and graphene, are currently very representative nonlinear scattering materials. Relevant documents such as "Carbon nanotubes for optical limiting" published in the SCI journal "Carbon" (2002, No. 10, Volume 40, pages 1789-1797), which propose an optical limiting device based on carbon nanotube dispersion liquid, and use Z-scan and pump-probe methods for detailed performance characterization; and the US patent "BROADBAND OPTICALLIMITER BASED ON NANO-GRAPHENE AND METHOD OF FABRICATINGSAME" (No. US20110304934A1) based on single-layer, few-layer graphene and nano-gold Optical limiter for particle dispersions. The above optical limiter based on nonlinear scattering has a strong nonlinear response and can work in a wide band from ultraviolet to infrared; and the new nanomaterial is not easy to agglomerate compared with the traditional carbon black suspension, and the stability of the device is improved. Big improvement. However, due to the limitation of the nonlinear scattering mechanism, these single-mechanism simple devices can only respond significantly to lasers with significant thermal effects (nanosecond or longer pulse width), but respond to ultrashort pulses (picoseconds and below) Very weak or even no optical limiting effect, which is limited in practical applications. The latter, such as "Molecular Engineering of Peripherally And Axially Modified Phthalocyanines" published in the SCI magazine "Advanced Materials" (No. 15, March 2003, pages 22-32) and "Porphyrins and phthalocyanines as materials for Optical limiting" (Vol. 141, Issue 3, 2004, pages 231-243), the phthalocyanines, porphyrins and their metal derivatives studied in this paper are typical nonlinear absorbing materials with large nonlinear absorption coefficient and very Fast response time, can be used for ultra-short pulse laser protection. However, nonlinear absorbing materials rely on the transition between energy levels of molecules, and the working wavelength is generally narrow. For example, phthalocyanine works in the visible light band (420nm-650nm), and cannot be used alone to manufacture broadband optical limiters.

The commonality of the above single material and single system is that the characteristics of optical limiting are determined by the characteristics of the material itself, which greatly limits the adjustment space. However, in practical applications, the light intensity allowed by the target is uncertain.

To make up for the shortcoming of a single mechanism in a single material, conjugated and nonconjugated hybrids of two different nonlinear materials have also been investigated. In Advanced Materials, Enhanced Optical Limiting Effects in Porphyrin-Covalently Functionalized Single-Walled Carbon Nanotubes (2008, Issue 20, pp. 511–515) and in Chemical Physics letters, Linear and nonlinear spectroscopic studies of phthalocyanine-carbonine-endblon "(2008 Issue 465, pp. 265-271), the nonlinear properties of porphyrin-functionalized carbon nanotube solution (conjugated mixing) and carbon nanotube phthalocyanine mixture (non-conjugated mixing) were respectively characterized. Porphyrin-functionalized carbon nanotubes exhibit good nonlinear properties due to the electron transfer between porphyrin molecules and carbon nanotubes. However, this method is complicated to prepare, requires precise reaction conditions, and the types of materials used are also limited. Although the carbon nanotube phthalocyanine mixture (non-conjugated mixture) can partially adjust the optical limiting curve, nonlinear tests show that its optical limiting performance is not good enough to meet the requirements of practical applications.

Contents of the invention

In view of the shortcomings and deficiencies of the above methods, the present invention proposes a double-layer cascaded optical limiter, which can adjust the optical limiter curve, and can realize a wide working band and a wide response time domain.

Technical solution of the present invention is as follows:

A double-layer cascaded optical limiter, including a nonlinear medium and a transparent container carrying the medium, is characterized in that: the transparent container is a double-cavity structure arranged adjacently; There are nonlinear scattering materials and inverse saturable absorbing materials.

The nonlinear scattering material is a dispersion of single-walled carbon nanotubes in dimethylformamide.

The reverse saturated absorption material is a solution of 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine zinc in dimethylformamide.

The arrangement sequence of the nonlinear media is arranged according to requirement.

Compared with the prior art, the present invention has the following advantages:

1. It can broaden the working range of the device. If the organic dispersion of single-walled carbon nanotubes and zinc phthalocyanine solution are contained at the same time, the device has optical limiting effect on the wide band from ultraviolet to near infrared, and wide time domain laser from long pulse to ultrashort pulse (ps).

2. By changing the type and material concentration of each nonlinear medium, the adjustment of the optical limiting curve can be realized.

Description of drawings

Fig. 1 is the structural representation of double-layer cascaded optical limiter of the present invention

Figure 2 is the experimentally measured relationship between the effective nonlinear absorption coefficient and the light intensity of the optical limiter, which is a double-layer optical limiter.

Fig. 3 is the optical limiting curve of the optical limiter calculated according to the experimental data, that is, the relationship between the light transmittance and the incident light intensity, and the optical limiter is the same as that in Fig. tube (SWNT) and zinc phthalocyanine (ZnPc) double-layer optical limiter.

Fig. 4 is the optical limiting curve of the optical limiter measured experimentally, that is, the relationship between light transmittance and incident light intensity. Double layer optical limiter for cyanine solution.

detailed description

The present invention will be further described below in conjunction with accompanying drawing and example, but these explanations can not be interpreted as limiting the scope of the present invention, and the protection scope of the present invention is defined by the claims, and any modification on the basis of the claims of the present invention is protection scope of the present invention.

Please refer to FIG. 1 first. FIG. 1 is a schematic diagram of the structure of the double-layer cascaded optical limiter of the present invention. In the figure, the nonlinear medium 1 is loaded in the cavity in the transparent glass container 2, and the number of the cavity is determined according to the need.

This example illustrates that a double-layer cascaded optical limiter can be formed by using two materials, carbon nanotubes and zinc phthalocyanine, and the adjustment of nonlinear response can be realized by changing the concentration and the type of medium in each layer. The performance of the optical limiter obtained in this embodiment is measured using the aperture z-scanning method, and the laser used in the experiment is 532 nm, 6 ns. The preparation method of the double-layer cascaded optical limiter is as follows:

(1) Add carbon nanotube (SWNT) powder into dimethylformamide (abbreviated as DMF) with an initial concentration of 0.05g/l. The resulting mixture was dispersed by ultrasonication for 2 min with a high-energy ultrasonic rod, then placed in an ultrasonic pool for 4 h, and finally ultrasonicated for 1 min with an ultrasonic rod. The obtained product was centrifuged at 5500 rpm for 90 min to remove aggregates to obtain a stable non-settling dispersion, which was diluted with DMF to different concentrations for use. Zinc phthalocyanine (2,9,16,23-tetra-tert-butyl-29H,31H-zinc phthalocyanine) was also dissolved in DMF at different concentrations.

(2) A quartz glass container as shown in FIG. 1 is manufactured, and the number of cavities is two. A 0.033 mg/mL single-walled carbon nanotube (SWNT) dispersion and a 0.1 mg/mL zinc phthalocyanine (ZnPc) solution were injected into two cavities of a quartz glass container to obtain an optical limiter containing the two materials . According to the sequence of light passing through the medium, it can be divided into two cases. If the laser passes through the SWNT dispersion first and then through the ZnPc solution, it is recorded as SWNT-ZnPc, and vice versa. The results of the nonlinear test are shown in Figure 2 and Figure 3. It can be seen from the figures that changing the order of nonlinear media can affect the nonlinear performance and optical limiting curve of the device.

(3) By changing the concentration of the solution, optical limiters with different performances can be obtained. The results of the nonlinear test are shown in Figure 4. It can be seen that the concentration matching and the sequence of the media can change the optical limiting curve of the device.

Claims (1)

1. a double-layer cascade connection optical limiter, including nonlinear dielectric and the transparent vessel of this medium of carrying, its feature It is: be the double cavity structure of arranged adjacent in described transparent vessel；It is respectively provided with single wall carbon in described two-chamber to receive Mitron dispersion liquid in dimethylformamide and 2,9,16,23-tetra-tert-29H, 31H-Phthalocyanine Zinc is at dimethyl methyl Solution in amide；Putting in order of described nonlinear dielectric arranges as required.