CN101051166A - Method for reducing full light switch pump power, full light switch and its preparing method - Google Patents

Abstract

The invention provides a method for reducing the pumping power of an all-optical switch, which belongs to the technical field of all-optical switches. The method comprises: adding a laser dye to an organic conjugated polymer material to prepare a composite material, using the composite material to prepare a two-dimensional photonic crystal; coupling a detection laser to the above-mentioned two-dimensional photonic crystal, and the wavelength of the detection laser is located in the above-mentioned two-dimensional The edge of the photonic bandgap of the photonic crystal; the pump laser is used to excite the above-mentioned two-dimensional photonic crystal to realize the all-optical switch, and the wavelength of the pump laser is located in the linear absorption band of the optical dye of the above-mentioned two-dimensional photonic crystal. The invention can reduce the pumping power to hundreds of KW/cm ² to MW/cm ² . The present invention also provides an all-optical switch and a preparation method thereof. The all-optical switch is a two-dimensional photonic crystal, and the two-dimensional photonic crystal is an organic thin film etched with square lattice periodic air holes. Conjugated polymers are added with laser dyes.

Description

Method for reducing pumping power of all-optical switch, all-optical switch and preparation method thereof

technical field

The invention belongs to the technical field of all-optical switches, and in particular provides a two-dimensional organic photonic crystal all-optical switch with low pumping power and ultra-fast response.

Background technique

Photonic crystal is a new type of artificially designed photonic material formed by two or more materials with different dielectric functions arranged periodically in space. It has unique characteristics of controlling photon transmission state. It is used in optical communication, Optical computing and ultra-fast information processing and other fields have very important applications.

The photonic bandgap comes from the modulation of the spatially periodic dielectric function on the incident light wave, and the light whose wavelength (or frequency) falls within the photonic bandgap will be completely reflected back and cannot pass through the photonic crystal. In terms of physical mechanism, the interference effect between light waves strongly scattered by periodic dielectric structures creates a forbidden band for photon transmission. Therefore, the greater the dielectric constant contrast, the stronger the incident light will be scattered, and the more obvious the photonic bandgap effect; the better the periodicity of the spatial structure, the stronger the interference effect, and the more obvious the photonic bandgap effect (Document 1, J.D.Joannopoulos , R.D.Meade, and J.N.Winn, Photonic crystals: Molding the Flow of Light, Princeton University press, Princeton, 1995).

The all-optical switch controls the transmission state of another beam of light by one beam of light, and is a very important integrated photonic device. Fast switching time response, high switching contrast, and low pump power are important indicators of photonic crystal all-optical switches. At present, many experimental studies on photonic crystal all-optical switches are based on common semiconductor materials. The photonic crystal is pumped by fs laser to excite the semiconductor free carriers to change the refractive index of the material, thereby changing the effective refractive index of the photonic crystal, and the photonic band gap occurs. Move to realize femtosecond subpicosecond ultrafast response photonic crystal all-optical switch, but the required pump light intensity is in the order of GW/cm ² (document 2, M.Shimizu, T.Ishihara.Subpicosecond transmission change insemiconductor embedded photonic crystal slab: Toward ultrafastoptical switching.Appl.Phys.Lett.2002, 80:2836-2838); Documents 3 and 4 use polystyrene as a nonlinear optical material to prepare two-dimensional photonic crystals, using photonic bandgap migration and defects State shifting realizes the all-optical switching effect, however, the required pump light intensity is greater than 15GW/cm ² (document 3, XYHu, YHLiu, J.Tian, BYCheng, and DZZhang.Ultrafastall-optical switching in two-dimensionala organic photonic crystal.Appl.Phys.Lett., 2005, 86:121102; Literature 4, XYHu, QHGong, YHLiu, BYCheng, and DZZhang. All-optical switching of defectmode in two-dimensional nonlinear organic photonic crystals.Appl.Phys.Lett. , 2005, 87:231111). Documents 5 and 6 introduce defects into semiconductor photonic crystals, use the movement of defect states to realize photonic crystal all-optical switches, and improve the quality factor of defect modes by designing the structure of photonic crystals and defects, thereby greatly reducing the required The pump light intensity is high, and the picosecond fast response photonic crystal all-optical switch is realized by using the low pump light intensity of tens of KW/cm ² , but its transmittance is very low, only a few percent of the transmittance, and The preparation process is relatively complicated, and it is difficult to realize artificial regulation (document 5, F.Raineri, C.Cojocaru, P.Monnier, A.Levenson, R.Raj, C.Seassal, X.Letartre, and P.Viktorovitch, Ultrafastdynamics of the third -order nonlinear response in a two-dimensionalInP-based photonic crystal. Appl. Phys. Lett., 2004, 85: 1880-1882; Literature 6, T. Tanabe, Masaya Notomi, S. Mitsugi, A. Shinya, and E. Kuramochi, All-optical switches on a silicon chip realized using photonic crystal nanocavities. Appl. Phys. Lett., 2005, 87: 151112).

Patent 1 (Application No. 200610072799.0) uses polystyrene as a nonlinear optical material to construct a two-dimensional organic photonic crystal, and uses the third-order nonlinear optical Kerr effect of polystyrene to move the photonic band gap under the action of pump light. All-optical switch; Patent 2 (Application No. 03100044.4) uses ferroelectric materials as nonlinear optical materials to construct two-dimensional ferroelectric photonic crystals, using the third-order nonlinear optical Kerr effect of ferroelectric materials, photon bands under the action of pump light gap migration to realize all-optical switch; patent 3 (application number 02160207.7) uses semiconductor materials as nonlinear optical materials to construct two-dimensional photonic crystals with defect states, and utilizes the third-order nonlinear optical Kerr effect of semiconductor materials to pump The defect state moves under the action of light to realize the all-optical switch. The methods for realizing photonic crystal all-optical switches provided by these patents are realized by the use of common nonlinear optical materials. Due to the small nonlinear coefficient of these materials, very high pump light on the order of GW/ ^cm2 is required. powerful.

Contents of the invention

The object of the present invention is to provide a two-dimensional organic photonic crystal all-optical switch with low pump power and ultra-fast response.

Above-mentioned purpose of the present invention is achieved by following technical scheme:

A method for reducing the pumping power of an all-optical switch, the steps comprising:

(1) Prepare a composite material by doping an organic conjugated polymer with a laser dye, and use the composite material to prepare a two-dimensional photonic crystal;

(2) coupling the detection laser light into the above-mentioned two-dimensional photonic crystal, the wavelength of the detection laser light is located at the edge of the photonic band gap of the above-mentioned two-dimensional photonic crystal;

(3) Exciting the two-dimensional photonic crystal with a pump laser to realize the all-optical switch, the wavelength of the pump laser is located in the linear absorption band of the laser dye of the two-dimensional photonic crystal.

An all-optical switch, which is a two-dimensional photonic crystal, is characterized in that: the two-dimensional photonic crystal is an organic thin film etched with square lattice periodic air holes, and the organic thin film is an organic conjugated polymer doped with a laser dye.

The lattice constant of the two-dimensional photonic crystal ranges from 200nm to 1000nm.

The air hole radius of the two-dimensional photonic crystal is between 50nm and 500nm.

The laser dyes are: cyanine dyes, coumarin dyes, oxazine dyes or scintillation materials.

The organic conjugated polymer is: an organic conjugated polymer composed of chain molecules containing unsaturated covalent π bonds, and a large conjugated ring formed by alternately bonding unsaturated covalent π bonds and saturated covalent σ bonds Organic conjugated polymers composed of fullerene molecules or organic conjugated polymers composed of fullerene molecules.

The thickness range of the organic thin film is 250nm-500nm.

A method for preparing an all-optical switch, comprising:

(1) adding a laser dye to an organic conjugated polymer to obtain a composite organic polymer, and preparing the composite organic polymer into a solution with an organic solvent;

(2) preparing an organic film from the organic polymer solution;

(3) Periodic air holes in a square lattice are etched on the organic thin film to form a two-dimensional photonic crystal.

Using the chemical organic polymerization method, a laser dye molecule is connected to an organic conjugated polymer molecule through a chemical bond, and the laser dye is added to the organic conjugated polymer to obtain a composite organic polymer, which is mixed with an organic solvent. The composite organic polymer is prepared into a solution, and the concentration range of the composite organic polymer is 1% to 30%.

The method of physical organic polymerization is adopted, and the organic conjugated polymer and the laser dye are respectively prepared into solutions by using an organic solvent, and the organic conjugated polymer solution and the laser dye solution are mixed to realize adding the laser dye to the organic conjugated polymer. Among them, the organic conjugated polymer is prepared into a solution with an organic solvent, and the concentration of the organic conjugated polymer is in the range of 1% to 20%; the laser dye is prepared in a solution with an organic solvent, and the concentration of the laser dye is in the range of 10% to 30%. %.

Organic solvents are non-polar organic solvents, such as toluene, ethanol, benzene, ether, tetrahydrofuran, etc.

Principle of the invention

1. Third-order nonlinear optical Kerr effect

According to the third-order nonlinear optical Kerr effect, the nonlinear optical material is excited by the pump laser, and its refractive index n will change.

$\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&Delta;\; n</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 120</span>}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; cn</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, n ₀ is the linear refractive index of the material, c is the speed of light in vacuum, x ⁽³⁾ is the third-order nonlinear susceptibility of the material, _Re x ⁽³⁾ represents the third-order nonlinear susceptibility x ^{( 3)} The value of the real part of , I is the pump light intensity, and π is the constant 3.14 (Document 7, edited by Qian Shixiong and Wang Gongming, Nonlinear Optics—Principles and Progress, Shanghai: Fudan University Press, 2001 edition).

2. Mechanism of photonic bandgap migration

The photonic bandgap transfer mechanism utilizes the third-order nonlinear optical Kerr effect of the material. The probe light is selected to be located at the edge of the photonic band gap, and the probe light cannot pass through the photonic crystal at the beginning. According to the third-order nonlinear optical Kerr effect, the refractive index of the material is proportional to the pump light intensity. If the nonlinear material has a positive third-order nonlinear susceptibility, the refractive index of the material will increase under the action of pump light, which will increase the effective refractive index of the photonic crystal and move the photonic band gap to the long-wave direction. If the nonlinear material has a negative third-order nonlinear susceptibility, the refractive index of the material will decrease under the action of pump light, which makes the effective refractive index of the photonic crystal smaller, and the photonic band gap moves to the short-wave direction. At this time, the probe light is located in the conduction band and can pass through the photonic crystal. In this way, the photonic band gap is shifted through the excitation of the pump light, thereby realizing the on-off control of the probe light (document 8, Scalora M, Dowling JP, Bowden C M and Bloemer M J. Optical limiting and switching of ultrashort pulses in nonlinear photonic band gap materials. Phys. Rev. Lett., 1994, 73: 1368-1371).

3. Evanescent wave coupling method

The incident light is coupled into the photonic crystal by using the evanescent wave coupling method. This is a commonly used energy coupling method between incident light and thin-film waveguide in the field of integrated optics. As long as the incident angle of the incident light at the bottom of the prism is adjusted to be greater than the total reflection angle, the incident light can be coupled into the photonic crystal. Use a clamp to press the prism on the organic polymer waveguide, leaving only a very narrow air gap s between the two, which constitutes an evanescent wave coupling system (Document 9, edited by She Shouxian. Fundamentals of Guided Wave Optics and Physics. North Traffic University Press. 2002 edition). n _p , n ₁ , n ₂ and n ₃ in the figure represent the refractive index of prism, thin film waveguide, substrate and air gap respectively, and n _p >n ₁ >n ₂ >n ₃ ; h represents the thickness of thin film waveguide; s is the thickness of the air gap; θ _p is the incident angle of the laser beam at the bottom of the prism; θ ₁ is the incident angle of the zigzag light of the guided mode on the upper and lower interfaces of the film; W is the width of the incident beam. When the prism and the waveguide are close to each other, the gap becomes very small, so that the tails of the evanescent field of the prism mode in the air gap and the tails of the evanescent field of the guided wave mode overlap each other, thus forming a leaky waveguide with a distorted refractive index distribution system, leading to the coupling between the prism mode and the waveguide mode, coupling energy from the incident laser beam into the waveguide mode, thereby realizing the incoupling from the incident beam to the waveguide. Similarly, through the coupling effect of the evanescent wave field between the prism mode and the guided wave mode, the energy of the guided wave mode in the waveguide can also be coupled out of the waveguide, thereby realizing output coupling.

The advantages of the present invention are:

1. The third-order nonlinear coefficient of the composite material is 1 to 2 orders of magnitude larger than that of the undoped organic conjugated polymer material, which can effectively reduce the excitation power of the pump laser required to achieve the switching effect, and can achieve low pump power Photonic crystal all-optical switch, the pump power can be reduced to hundreds of KW/cm ² to MW/cm ² .

2. The time response of the two-dimensional organic photonic crystal all-optical switch is determined by the nonlinear time response characteristics of the composite material, in the order of picoseconds to sub-picoseconds.

3. Two-dimensional organic photonic crystals are prepared by focused ion beam etching micromachining technology, which is simple in preparation technology and easy to integrate.

Description of drawings

Fig. 1 is a schematic diagram of the connection between the all-optical switch and the waveguide of the present invention;

Fig. 2 is a schematic diagram of the all-optical switch of the present invention in the "on" state;

Fig. 3 is a schematic diagram of the all-optical switch of the present invention in the "off" state;

Fig. 4 is the two-dimensional photonic crystal prepared by the present invention;

Fig. 5 is a schematic diagram of a device for detecting photonic crystal optical switch characteristics of the present invention;

Fig. 6 is the long-wave band edge of the photonic crystal photonic band gap prepared by the present invention;

Fig. 7 is the time response curve of the photonic crystal optical switch prepared by the present invention;

Figure 8 shows the movement of the long-wave band edge of the photonic bandgap after adding pump light to the photonic crystal prepared by the present invention, the pump light energy (■)0.132nJ.(▲)0.197nJ.(●)0.395nJ.()0.527 nJ.(★)0.592nJ.(◆)0.658nJ;

Fig. 9 is a graph showing the variation curve of the migration amount of the long-wave band edge of the photonic bandgap of the photonic crystal prepared by the present invention as a function of pumping light energy.

Detailed ways

1. Preparation of two-dimensional photonic crystals:

1. Selection of laser dyes:

Laser dye of the present invention is divided into four classes according to chemical structure, (1) cyanine dye, its laser range is 540-1200nm; (2) coumarin dye, its laser range is 425-565nm; (3) oxazine class The dye has a laser range of 650-700nm; (4) the scintillation material is an aromatic compound containing oxazine, oxadiazole, and benzoxazole rings, and is a laser dye in the violet to ultraviolet region.

2. Selection of organic conjugated polymers:

Organic conjugated polymers composed of chain molecules containing unsaturated covalent π bonds: such as polydiacetylene (PDA), polyacetylene (PA), polythiophene (PT), polystyrene (PS), etc.;

Organic conjugated polymers composed of unsaturated covalent π bonds and saturated covalent σ bonds alternately bonded to form large conjugated cyclic molecules: such as phthalocyanine, bufen, etc.;

An organic conjugated polymer composed of fullerene molecules, carbon 60, carbon 70, etc.

3. Adding laser dyes to organic conjugated polymers:

(1) Chemical method:

A chemical organic polymerization method is used to connect a laser dye molecule to an organic conjugated polymer molecule through a chemical bond, so as to realize the addition of laser dyes to the organic conjugated polymer. This synthesis forms a new composite organic compound material. Chemical organic polymerization methods mainly include: sol-gel method, monomer in situ polymerization method, etc.

(2) Physical method:

The organic conjugated polymer and the laser dye are prepared into solutions using a chemical solvent, and the organic conjugated polymer solution and the laser dye solution are mixed to disperse the laser dye molecules in the middle of the organic conjugated polymer molecules. Strong interactions with no chemical bonds between them. The result is a mixed solution containing laser dye molecules and organic conjugated polymer molecules.

4. Preparation of organic polymer solution:

(1) If the laser dye is added to the organic conjugated polymer by chemical method, the obtained organic compound is made into a solution with a concentration of 1% to 30%. The organic solvent used is a non-polar organic solvent, such as toluene, ethanol, benzene, ether, tetrahydrofuran and the like.

(2) If the laser dye is added to the organic conjugated polymer by physical methods, first prepare the organic conjugated polymer solution with a concentration of 1% to 20%; secondly, prepare the laser dye solution with a concentration of 10% to 30% %, finally, the two solutions are mixed to prepare an organic polymer solution. The organic solvent used is a non-polar organic solvent, such as toluene, ethanol, benzene, ether, tetrahydrofuran and the like.

5. Prepare an organic thin film with the organic polymer solution:

Organic thin films were prepared by spin-coating method. That is, organic films with different thicknesses can be prepared by controlling the rotational speed. The equipment used is a plastic throwing machine.

The specific steps are:

1. Clean the quartz substrate with ethanol. The size of the quartz substrate can be 2cm in length, 2cm in width, and 180μm in thickness;

2. Fix the quartz substrate on the turntable, and drop 0.5ml of the prepared solution on the substrate;

3. Turn on the power to throw the film, parameter setting: speed 1000 ~ 3000 rpm;

The prepared organic polymer film has a thickness of 300 nm and a circular area with a diameter of 1 cm. An organic polymer film was prepared.

6. Etched with square lattice periodic air holes on the organic film to form a two-dimensional photonic crystal:

The organic polymer film was etched by focused ion beam (FIB) to form a two-dimensional square lattice photonic crystal.

2. Realization of two-dimensional organic photonic crystal all-optical switch:

The connection between the photonic crystal all-optical switch and the waveguide is shown in Figure 1:

The photonic crystal optical switch is connected between the waveguide 1 and the waveguide 2, and the incident light beam enters the photonic crystal optical switch from the waveguide 1.

If no control light (that is, pump light) is added, the photonic crystal all-optical switch is in an "on" state, as shown in FIG. 2 . At this moment, the waveguide 1 and the waveguide 2 are connected, and the incident light beam can continue to propagate in the waveguide 2 through the photonic crystal.

If control light (that is, pump light) is added, the photonic crystal all-optical switch is in the “off” state, as shown in FIG. 3 . The incident beam will be completely reflected by the photonic crystal and cannot pass through the photonic crystal. At this time, waveguide 1 and waveguide 2 are completely disconnected, and no light propagates in waveguide 2.

The implementation and test results of a two-dimensional organic photonic crystal all-optical switch with low pump power and ultra-fast response are given below.

1. Preparation of two-dimensional photonic crystal:

The organic polymer is selected from the high-polymerization polystyrene with a molecular weight of 8,000,000 provided by Fluka Chemie; to switch and control the light with a wavelength of about 800nm, the wavelength of the pump laser is located in the linear absorption band of the laser dye, and the laser dye is selected as 3. 3'-diethyl-5,5'-dichloro-11-diphenylamino-10,12-ethylidene salivatricarbonate perchlorate (IR140), the absorption peak of the IR140 laser dye is 810nm, using Toluene solvent, first determine the concentration of polystyrene solution:

The mass ratio of polystyrene to toluene is 1:14, and the weight ratio of laser dye to toluene is 1:1500.

A 300nm-thick composite film was prepared by spin coating, and the substrate material used for the preparation of the film was a clean quartz plate with a length and width of 2 cm and a thickness of 180 μm. After the thin film is made, focused ion beam etching (FIB) is used to prepare a two-dimensional square lattice photonic crystal. The 800nm probe light needs to be controlled, the lattice constant is 284nm, and the air hole radius is 110nm. The area of the entire photonic crystal is 3um*100um. Because polystyrene is an insulating material, it cannot be etched directly with a focused ion beam. Therefore, a gold film with a thickness of 10 nm must be evaporated on the polystyrene film before etching. After the etching is completed, the photonic crystal is removed with water. gold film on it. The prepared photonic crystal is shown in Fig. 4 .

2. Measuring device:

As shown in Figure 5, the laser is a titanium-doped sapphire laser system pumped by a semiconductor laser. The pulse width is 120 femtoseconds, the repetition frequency is 76MHz, and the wavelength is tunable in the range of 790-860nm. The laser beam is divided into two beams by a 1:1 beam splitter 2, one beam is used as pump light, and the other beam is used as probe light.

The pumping optical path includes a delay line 3, a 45° total reflection mirror 4, an attenuation plate 5, and a focusing lens 6; the beam splitter 2 is located between the laser 1 and the delay line 3, and forms an angle of 45° with the pumping optical path, and delays 3 pairs The pump laser is 180° non-collinear total reflection, the 45° total reflection mirror 4 is on the reflection optical path of the delay line 3, and the attenuator 5 for adjusting the intensity of the pump laser light is placed between the half mirror 4 and the focusing lens 6 ;

The detection optical path includes a 45° total reflection mirror 7, a pair of aperture apertures 8, an evanescent wave coupling system 9, and a focusing lens 11; the beam splitter 2 is located between the laser 1 and the total reflection mirror 7, and the diameter of the aperture aperture pair 8 is 1 mm, located between the total reflection mirror 7 and the input coupling prism of the evanescent wave coupling system 9 to collimate and attenuate the detection beam, the detection light enters the input coupling prism of the evanescent wave coupling system 9, passes through the photonic crystal 10 and then passes through another A prism coupling output;

The signal processing system includes a synchronous detection fiber optic spectrometer 11 and a computer 12; the fiber optic spectrum 11 collects and detects laser signals and inputs them into the computer 12 for data collection and processing;

3. Determine the position of the long-wave band edge of the photonic band gap of the photonic crystal:

Block the pump light, adjust the incident angle of the probe light at the bottom of the prism to be greater than the total reflection angle, couple the probe light into the photonic crystal, and measure the relationship between the transmittance of the probe light and the wavelength. Perform data processing to determine the position of the long-wave band edge of the photonic bandgap. As shown in Figure 6, the entire band edge is very steep and distributed within the range of 1.5nm. The wavelength of the probe light for determining the all-optical switching effect is 801.8nm.

4. Time response characteristics of all-optical switches:

Adjust the band-pass attenuator to set the pump laser energy passing through the photonic crystal to 0.35nJ; adjust the delay line 3, measure the change curve of the transmittance of the probe laser with time delay, and perform a fitting, as shown in Figure 7: The probe laser transmittance decreases with the overlapping of the pump pulse and the probe pulse, and its transmittance reaches a minimum at the position of zero time delay, indicating that the photonic bandgap shifts to the long-wave direction. The falling edge of the signal curve is about 200 fs, which is equivalent to the pulse width of the pump light. The rising edge has a relaxation time of 1 ps, and the FWHM of the response signal is about 1.0 ps. It can be seen that the response time of the photonic crystal all-optical switch has reached ps class. The relaxation time of the ps order is determined by the vibrational relaxation on the potential energy surface of the excited state of the laser dye IR140 and the photoconversion process from cis to trans.

5. Optical switch comparison:

When there is no pumping light, the maximum transmittance of the probe light is 89%. When the energy of the pump light is about 0.5nJ, the transmittance of the probe light reaches the minimum value of 30%, and the switching process can be realized, and the switching contrast is 59%.

6. Pump light intensity:

In this experimental system, the pulse width of the pump light is 120 femtoseconds, and the spot area focused on the photonic crystal is about 0.01cm ² , so the pump power to realize the optical switch is determined to be hundreds of KW/cm ² to MW/cm ² . It can be seen from the experimental results that the third-order nonlinear coefficient of the composite material is 1-2 orders of magnitude larger than that of the undoped organic conjugated polymer material, and a photonic crystal all-optical switch with low pump power can be realized.

7. This method can also determine the migration of the photonic bandgap:

Adjust the band-pass attenuator so that the energy of the pump laser increases continuously from 0 to 1nJ, and measure the position of the long-wave band edge of the photonic bandgap of the two-dimensional organic photonic crystal with the change curve of the pump laser energy. As shown in Figure 8, as the energy of the pump light increases, the refractive index of the material increases, and the band edge moves to the long-wave direction. When the energy of the pump light is 0.658nJ, the band edge moves by 2.2nm. Calculate the migration amount of the photonic bandgap, and draw the change curve of the migration amount of the photonic bandgap with the intensity of the pump light, as shown in Figure 9, with the increase of the energy of the pump laser, the photonic bandgap is continuously adjustable.

The above is a detailed description of the process steps of the preferred embodiment of the present invention, but obviously, researchers in the technical field of the present invention can make non-essential changes in form and content according to the above steps without departing from the essential protection of the present invention. Therefore, the invention is not limited to the exact forms and details described above.

Claims (13)

1. A method for reducing the pumping power of an all-optical switch, the steps comprising: (1) Prepare a composite material by doping an organic conjugated polymer with a laser dye, and use the composite material to prepare a two-dimensional photonic crystal; (2) coupling the detection laser light into the above-mentioned two-dimensional photonic crystal, the wavelength of the detection laser light is located at the edge of the photonic band gap of the above-mentioned two-dimensional photonic crystal; (3) Exciting the above-mentioned two-dimensional photonic crystal with a pump laser to realize an all-optical switch, the wavelength of the pump laser is located in the linear absorption band of the optical dye of the above-mentioned two-dimensional photonic crystal. 2. An all-optical switch, which is a two-dimensional photonic crystal, is characterized in that: the two-dimensional photonic crystal is an organic thin film etched with square lattice periodic air holes, and the organic thin film is organic conjugated polymer doped Miscellaneous laser dyes. 3. The all-optical switch according to claim 2, wherein the lattice constant of the two-dimensional photonic crystal ranges from 200nm to 1000nm. 4. The all-optical switch according to claim 2 or 3, characterized in that the air hole radius of the two-dimensional photonic crystal is between 50nm and 500nm. 5. The all-optical switch according to claim 2, wherein the laser dyes are cyanine dyes, coumarin dyes, oxazine dyes or scintillation materials. 6. The all-optical switch as claimed in claim 2 or 5, characterized in that: the organic conjugated polymer is an organic conjugated polymer composed of chain molecules containing unsaturated covalent π bonds, and is composed of unsaturated Covalent π bonds and saturated covalent σ bonds are alternately bonded to form organic conjugated polymers composed of large conjugated ring molecules or organic conjugated polymers composed of fullerene molecules. 7. The all-optical switch according to claim 2, wherein the thickness of the organic thin film is in the range of 250nm-500nm. 8. A method for preparing an all-optical switch, comprising: (1) adding a laser dye to an organic conjugated polymer to obtain a composite organic polymer, and preparing the composite organic polymer into a solution with an organic solvent; (2) preparing an organic film from the organic polymer solution; (3) Periodic air holes in a square lattice are etched on the organic thin film to form a two-dimensional photonic crystal. 9. The method for preparing an all-optical switch as claimed in claim 8, characterized in that: in step (1), a chemical organic polymerization method is used to connect a laser dye molecule to an organic conjugated polymer molecule through a chemical bond Above, realize the incorporation of laser dyes in organic conjugated polymers. 10. The method for preparing an all-optical switch as claimed in claim 8, characterized in that: in step (1), a physical organic polymerization method is used to prepare solutions of organic conjugated polymers and laser dyes with organic solvents, and the organic The conjugated polymer solution and the laser dye solution are mixed to realize adding the laser dye to the organic conjugated polymer. 11. The method for preparing an all-optical switch according to claim 9, characterized in that: the composite organic polymer is prepared into a solution with an organic solvent, and the concentration of the composite organic polymer ranges from 1% to 30%. 12. The method for preparing an all-optical switch according to claim 10, characterized in that: the organic conjugated polymer is prepared into a solution with an organic solvent, and the concentration range of the organic conjugated polymer is 1% to 20%; The solvent prepares the laser dye into a solution, and the concentration of the laser dye ranges from 10% to 30%. 13. The method for preparing an all-optical switch according to claim 8, 9, 10, 11 or 12, characterized in that the organic solvent is a non-polar organic solvent, such as toluene, ethanol, benzene, ether, tetrahydrofuran.

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