CN106324743A - Polarization beam splitter based on metal raster - Google Patents

Abstract

The invention belongs to the technical field of the optical device, and relates to a polarization beam splitter based on a metal raster. The main structure of the polarization beam splitter based on the metal raster comprises a covering film layer, a raster structure, a raster groove and a substrate. The upper surface of the raster structure is fixedly covered by the covering film layer, and the covering film layer is capable of realizing the function of a waveguide layer in the diffraction process of the raster structure and protecting the raster structure. The silver raster structure is used for preparing the parallelly distributed raster grooves through the etching technology. The raster groove is 300 nm in depth, the duty ratio of the raster is 0.21, and the raster period of the raster structure is 180 nm. The substrate of the SiO2 material is fixedly positioned on the lower surface of the raster structure. The polarization beam splitter based on the metal raster is on the basis of the silver raster structure, and has advantages of high diffraction efficiency, high extinction ratio, good polarization performance, good technology tolerance, simple main structure, convenient use, good market application prospect and friendly application environment. The spectral bandwidth is wide, and up to 207 nm. The performance can satisfy the requirements to the polarization beam splitter in the field of the optical device.

Description

A kind of polarization beam apparatus based on metal grating

Technical field:

The invention belongs to field of optical device technology, relate to a kind of polarization beam apparatus, particularly a kind of based on metal grating Polarization beam apparatus, should polarization beam apparatus based on metal grating on the basis of rigorous couple-wave analysis, using argent as The material of polarization beam-splitting grating, performance is better than tradition beam splitter, is the optical element of a kind of function admirable.

Background technology:

Along with arriving and the development of science and technology of information age, we are the most slowly marched toward by era of electronic Information communication era, people obtain the demand of bulk information the most rapidly and promote electromagnetic theory and micro-processing technology Fast development, makes us have been able to by light wave as carrier wave, utilizes light wave to have high time, space-bandwidth product, high The concurrency of degree and non interference, it is possible to while high-speed transfer information, accomplish that light loss is little, the distortionless feature of signal, Carry out information transmission expeditiously.During utilizing light to carry out information transmission, for increasing bandwidth and reducing different interchannels Crosstalk need to use the different polarization states of light.And polarization beam apparatus is the indispensable photonic modulator in optical-fiber network assembly Part, it can split the light into the two orthogonal polarized light of bundle polarization mode, in order to adjust the polarization state of light, at polarization beam apparatus In, there is High Extinction Ratio, wide spectrum, wide viewing angle, the polarization beam apparatus of high-diffraction efficiency are then preferable photonic modulation devices.And Traditional polarization beam apparatus is to be broadly divided into two kinds, a kind of natural birefringence effect such as Thomson ribs based on some crystal Mirror and Nicol prism etc., this kind of beam splitter not only cost of manufacture is high, and bulky, and practicality is poor；Another kind is multilamellar The polarization beam apparatus of deielectric-coating, this polarization beam apparatus bandwidth of operation is little, and the thin film number of plies is the most, complex manufacturing technology degree pole Height, needs high uniformity and well-balanced property, and processing and manufacturing is extremely difficult, it is difficult to industrialized production, at the same time in terms of delustring Performance is the most not enough；Above two beam splitter is all difficult to reach the requirement of ideal photon modulation device.And sub-wave length metal grating tool There is at a relatively high optical property, be a kind of preferably photonic modulation device, sub-wavelength metal light compared to above two beam splitter Grid have the special nature that traditional raster does not has, and its absorbance and extinction ratio height, spectral width width, polarization property are good, Sub-wavelength optical elements application occupies critical role, and there is the advantages such as volume is little, easy of integration, thus by people's Extensive concern.In the prior art, there is no produce for the wave band that centre wavelength is 800nm based on metal polarization grating point Bundle device, therefore, relates to preparing a kind of polarization beam apparatus based on metal grating, using argent as the material of polarization beam-splitting grating Material, it is possible to keep high polarization beam splitting ability in the wide spectral range near 800nm wave band.

Summary of the invention:

It is an object of the invention to the shortcoming overcoming prior art to exist, for 800nm wave band, seek design a kind of based on The polarization beam apparatus of metal grating, this invention has high diffraction efficiency at 0 grade, simultaneously to the light wave of centre wavelength 800nm Light wave angle of incidence is when-27 ° to 27 ° of changes, and grating transmission and reflected extinction ratio are both greater than 20dB, diffraction efficiency and extinction ratio all Disclosure satisfy that the performance parameter of high-performance polarization beam apparatus.

To achieve these goals, the polarization beam apparatus agent structure based on metal grating that the present invention relates to includes: cover Epiphragma layer, optical grating construction, grating groove and pedestal, SiO₂The cover layer of material is flat film structure, the thickness of cover layer For 225nm, cover layer fixes the upper surface being covered in optical grating construction, and cover layer realizes in the diffraction process of optical grating construction Effect of ducting layer also can protect optical grating construction, and the material of optical grating construction is argent, passes through etch process at its upper surface Preparing the grating groove of block form distribution, the groove depth of grating groove is 300nm, and grating dutycycle is 0.21, the grating week of optical grating construction Phase is 180nm；SiO₂The pedestal of material is fixed and is placed at the lower surface of optical grating construction, in order to supporting & stablizing optical grating construction；Based on The main body parameter designing step of the polarization beam apparatus of metal grating is as follows:

Step 1: calculate transmission extinction ratio T that TM ripple is at 0 grade_CWith TE ripple 0 grade reflected extinction ratio R_C:

$T_C=10{\log }_{10}(T_0^{TM}/T_0^{TE})---\left(1\right)$

$R_C=10{\log }_{10}(R_0^{TE}/R_0^{TM})---\left(2\right)$

Wherein,Represent transmission and the diffraction efficiency of reflection of 0 grade of TM ripple respectively, Represent TE respectively Transmission that ripple is 0 grade and reflection diffraction efficiency；

Step 2: use genetic algorithm the parameter of optical grating construction to be optimized design, in order to realize TM ripple and TE wave polarization Beam splitting, determines genetic algorithm target equation and fitness function by analysis, and fitness function RMS is as follows in definition:

$RMS=mean(1./(T_0^{TM}+R_0^{TE})+T_0^{TE}+R_0^{TM})---\left(3\right)$

Wherein, RMS is the least, and the polarization beam splitting of optical grating construction is the most obvious；

Step 3: the design of Structural Parameters of polarization beam apparatus based on metal grating:

At centre wavelength 800nm, go out this optimal structure based on metal grating beam splitter by numerical simulation of optimum Parameter is as follows: the thickness D of cover layer₁For 225nm, dutycycle f of optical grating construction is 0.21, and groove depth D2 of grating groove is 300nm, the screen periods T of optical grating construction are 180nm, and the angle of incidence of light is 0 °；

4, diffraction efficiency and extinction ratio to the optical grating construction in step 3 are analyzed:

As follows by the diffraction efficiency of the optical grating construction in simulative optimization, step 3 and the analysis result of extinction ratio, incidence wave Long when 702-909nm changes, the TM absorbance of optical grating construction and TE reflectance are more than 95%, and incident wavelength is at 764-855nm During change, the TM reflectance of optical grating construction and TE absorbance are less than 1%；Incident wavelength when 747-854nm changes, optical grating construction Reflected extinction ratio more than 20dB, incident wavelength is when 700-900nm changes, and the transmission extinction ratio of optical grating construction is more than 27.4dB, therefore, polarization beam apparatus based on metal grating maintains high polarization in the wide spectral range of 702-909nm and divides Shu Nengli；Angle of incidence is when changing for-30.3 ° to 30.3 °, and the TM absorbance of optical grating construction and TE reflectance are more than 95%, incident Angle is when changing for-27 ° to 27 °, and TM reflectance and the TE absorbance of optical grating construction are respectively less than 1%；Angle of incidence is-27 ° to 27 ° of changes During change, the reflected extinction ratio of optical grating construction is all higher than 20dB, angle of incidence-35 ° to 35 ° change time, the extinction ratio of optical grating construction Being all higher than 29.2dB, when light vertical incidence, transmission and the reflected extinction ratio of optical grating construction are respectively 29.2dB and 39.5dB, Therefore, this invention maintains higher polarization beam splitting ability in the wide range of-27 ° to 27 °, according to above-mentioned analysis result Can be derived that, in 0 order diffraction level time, TM absorbance and the TE reflectance bandwidth of operation more than 95% of optical grating construction reaches 207nm, the angle excursion of the transmission of optical grating construction and reflected extinction ratio both greater than 20dB reaches 54 °, meets wide spectrum, width Visual angle, the design requirement of High Extinction Ratio；

5, process allowance analysis:

Due to control accuracy and the impact of micro-processing technology, the groove depth of grating groove, the thickness of cover layer and screen periods In preparation process, have error, and angle of incidence change all can produce impact to the polarization effect of invention；When fixing other ginsengs During number, cover layer is at 150-300nm, and when groove depth changes between 275-350nm, transmission extinction ratio is both greater than 25dB；Work as covering Film layer is at 217-242nm, and when grating groove deep changes between 259-315nm, reflected extinction ratio is both greater than 30dB；When grating is tied The grating groove deep of structure is when 259-315nm or cover layer thickness change between 217-242nm, and this optical grating construction is to light Grid groove deep and cover layer are respectively provided with bigger process allowance；When the angle of incidence of light wave changes between-30 ° to 30 °, light When grid cycle is between 50-187nm, the transmission extinction ratio of optical grating construction is all higher than 30dB；Screen periods is between 114-315nm Time, the reflected extinction ratio of optical grating construction is all higher than 30dB；Therefore, analyze from preparation technology angle, when light wave angle of incidence- When 30 ° to 30 ° or screen periods change between 114-187nm, the technique of angle of incidence and screen periods is held by optical grating construction Difference is relatively large, and the thickness of screen periods, grating groove deep and cover layer has bigger technique to prepare tolerance, it is possible to reduce The impact on polarization effect of the error in actual preparation.

Compared with prior art, based on silver optical grating construction, diffraction efficiency is high, extinction ratio is high, polarizability for the present invention Can be good, spectral bandwidth is the widest, it is possible to reach 207nm, and based on rigorous coupled wave approach, process allowance is good, and performance meets The requirement to polarization beam apparatus of the optics field；Its agent structure is simple, and service behaviour is high, and applied environment is friendly, before market Scape is wide.

Accompanying drawing explanation

Fig. 1 is the Geometric structure principium schematic diagram of the present invention.

Fig. 2 is the spectral curve of the optical grating construction diffraction efficiency that the present invention relates to.

Fig. 3 is the extinction ratio that the present invention relates to change curve with wavelength.

Fig. 4 is the diffraction efficiency that the present invention relates to change curve with angle of incidence.

Fig. 5 is the transmission that the present invention relates to and the reflected extinction ratio change curve with angle of incidence.

Fig. 6 (a) for the transmission extinction ratio that the present invention relates to the circle of equal altitudes of grating depth Yu cover layer thickness variation, Fig. 6 (b) for the reflected extinction ratio that the present invention relates to the circle of equal altitudes of grating depth Yu cover layer thickness variation.

The circle of equal altitudes that Fig. 7 (a) changes with angle of incidence with screen periods for the transmission extinction ratio that the present invention relates to, Fig. 7 (b) is The reflected extinction ratio that the present invention relates to is with the circle of equal altitudes of screen periods with angle of incidence change.

Detailed description of the invention

Below in conjunction with the accompanying drawings and by embodiment the present invention is described in further detail.

Embodiment:

The polarization beam apparatus agent structure based on metal grating that the present embodiment relates to includes: cover layer 1, optical grating construction 2, grating groove 3 and pedestal 4, SiO₂The cover layer 1 of material is flat film structure, and the thickness of cover layer 1 is 225nm, covers Epiphragma layer 1 is fixed uniform fold and is realized waveguide in the diffraction process of optical grating construction in the upper surface of optical grating construction, cover layer 1 Layer effect and optical grating construction 2 can be protected, at silver optical grating construction 2 upper surface by etch process prepare block form be distributed Grating groove 3, grating groove 3 groove depth is 300nm, and grating dutycycle is 0.21, and screen periods is 180nm；SiO₂The pedestal 4 of material is solid Fixation is at the lower surface of optical grating construction 2, in order to supporting & stablizing optical grating construction 2；It is described based on metal light that the present embodiment relates to The main body parameter designing step of the polarization beam apparatus of grid is as follows:

Step 1: calculate transmission extinction ratio T that TM ripple is at 0 grade_CWith 0 grade of TE ripple reflected extinction ratio R_C:

Using rigorous couple-wave analysis method to design this polarization beam apparatus based on metal grating, its performance evaluation parameter is main Including diffraction efficiency and extinction ratio, extinction ratio is to evaluate its polarization property most important performance parameter, and TM ripple is the transmission of 0 grade Extinction ratio T_CWith 0 grade of TE ripple reflected extinction ratio R_CIt is respectively as follows:

$T_C=10{\log }_{10}(T_0^{TM}/T_0^{TE})---\left(1\right)$

$R_C=10{\log }_{10}(R_0^{TE}/R_0^{TM})---\left(2\right)$

Wherein,Represent transmission and the diffraction efficiency of reflection of 0 grade of TM ripple respectively, Represent TE respectively Transmission that ripple is 0 grade and reflection diffraction efficiency；

Step 2: use genetic algorithm that grating structural parameter is optimized design, divide in order to realize TM ripple and TE wave polarization Bundle, determines genetic algorithm target equation, fitness function through mathematical analysis, and fitness function RMS is as follows in definition:

$RMS=mean(1./(T_0^{TM}+R_0^{TE})+T_0^{TE}+R_0^{TM})---\left(3\right)$

Wherein, RMS is the least, and the polarization beam splitting of optical grating construction 2 is the most obvious；

Step 3: the optimum structure parameter designing of polarization beam apparatus:

At centre wavelength 800nm, go out optimal structural parameters by numerical simulation of optimum as follows: the thickness of cover layer 1 Degree D₁For 225nm, dutycycle f of optical grating construction 2 is 0.21, and groove depth D2 of grating groove 3 is 300nm, and screen periods T is 180nm, The angle of incidence of light is 0 °；

Step 4: diffraction efficiency and extinction ratio to the structural parameters designed in step (3) are analyzed:

Through simulative optimization, the curve of spectrum of designed optical grating construction diffraction efficiency as in figure 2 it is shown, by figure it can be seen that From incident wavelength when 702-909nm, TM absorbance and TE reflectance are more than 95%, and incident wavelength is when 764-855nm, and TM is anti- Penetrate rate and TE absorbance less than 1%；From Fig. 3 it can be seen that when incidence wave changes from 747-854nm, reflected extinction ratio is more than 20dB, incident wavelength is when 700-900nm, and the transmission extinction ratio of this embodiment is more than 27.4dB, therefore, the base described in embodiment Polarization beam apparatus in metal grating maintains high polarization beam splitting ability in the wide spectral range of 702-909nm；By Fig. 4 energy Enough finding out, when angle of incidence is from-30.3 ° to 30.3 ° of changes, TM absorbance and TE reflectance are more than 95%, from-27 ° to 27 ° of changes During change, TM reflectance and TE absorbance are less than 1%；Fig. 5 it can be seen that angle of incidence from-27 ° to 27 ° change time, the present embodiment Reflected extinction ratio is both greater than 20dB, and angle of incidence is when-35 ° to 35 ° of changes, and the transmission extinction ratio of the present embodiment is both greater than 29.2dB, when light vertical incidence, transmission and reflected extinction ratio are respectively 29.2dB and 39.5dB, therefore, embodiment- Maintain higher polarization beam splitting ability in the wide range of 27 ° to 27 °, can be derived that according to above-mentioned analysis result, this reality Execute example TM absorbance and TE reflectance bandwidth of operation more than 95% in 0 order diffraction level time and reach 207nm, polarization beam apparatus The angle excursion of transmission and reflected extinction ratio both greater than 20dB reaches 54 °, meets wide spectrum, wide viewing angle, High Extinction Ratio Design requirement；

Step 5: process allowance analysis:

Due to control accuracy and the impact of micro-processing technology, the groove depth of grating groove 3, the thickness of cover layer 1, screen periods Can there is certain error in T in preparation process, and angle of incidence change all can produce impact to the polarization effect of embodiment；Fig. 6 A (), (b) are respectively transmission and the reflected extinction ratio circle of equal altitudes with grating groove 3 groove depth with the change of cover layer 1 thickness, by Fig. 6 (a) it can be seen that when fixing other parameters, cover layer is at 150-300nm, when groove depth changes between 275-350nm, transmission Extinction ratio is both greater than 25dB；Fig. 6 (b) it can be seen that when cover layer 1 at 217-242nm, grating groove 3 groove depth is at 259-315nm Between change time, reflected extinction ratio is both greater than 30dB；From the point of view of preparation technology angle, when grating groove 3 groove depth at 259-315nm or Being cover layer 1 thickness when changing between 217-242nm, grating groove 3 groove depth and cover layer 1 are all had by this optical grating construction 2 There is bigger process allowance；Fig. 7 (a), (b) are respectively transmission and reflected extinction ratio is contour with what angle of incidence changed with screen periods Figure, when angle of incidence changes between-30 ° to 30 °, during by Fig. 7 (a) it can be seen that screen periods is between 50-187nm, thoroughly Penetrate extinction ratio and be both greater than 30dB；During by Fig. 7 (b) it can be seen that screen periods is between 114-315nm, reflected extinction ratio is the biggest In 30dB；Therefore, analyze from preparation technology angle, when the angle of incidence of light wave at-30 °-30 ° or screen periods at 114- Between 187nm during change, this embodiment is relatively large to the process allowance of angle of incidence and screen periods, and therefore, this embodiment relates to And grating screen periods, grating groove 3 groove depth, the thickness of cover layer 1 have bigger technique to prepare tolerance, reduce reality The impact on polarization effect of the error in preparation.

Claims (1)

1. a polarization beam apparatus based on metal grating, it is characterised in that its agent structure includes: cover layer, grating are tied Structure, grating groove and pedestal, SiO₂The cover layer of material is flat film structure, and the thickness of cover layer is 225nm, coverlay The fixing upper surface being covered in optical grating construction of layer, cover layer realizes effect of ducting layer also in the diffraction process of optical grating construction Can protect optical grating construction, the material of optical grating construction is argent, prepares block form by etch process and be distributed at its upper surface Grating groove, the groove depth of grating groove is 300nm, and grating dutycycle is 0.21, and the screen periods of optical grating construction is 180nm；SiO₂ The pedestal of material is fixed and is placed at the lower surface of optical grating construction, in order to supporting & stablizing optical grating construction；Polarization based on metal grating The main body parameter designing step of beam splitter is as follows:

Step 1: calculate transmission extinction ratio T that TM ripple is at 0 grade_CWith TE ripple 0 grade reflected extinction ratio R_C:

$T_C=10{\log }_{10}(T_0^{TM}/T_0^{TE})---\left(1\right)$

$R_C=10{\log }_{10}(R_0^{TE}/R_0^{TM})---\left(2\right)$

Wherein,Represent transmission and the diffraction efficiency of reflection of 0 grade of TM ripple respectively, Represent TE ripple 0 respectively The transmission of level and reflection diffraction efficiency；

Step 2: use genetic algorithm that the parameter of optical grating construction is optimized design, divide in order to realize TM ripple and TE wave polarization Bundle, determines genetic algorithm target equation and fitness function by analysis, and fitness function RMS is as follows in definition:

$RMS=mean(1./(T_0^{TM}+R_0^{TE})+T_0^{TE}+R_0^{TM})---\left(3\right)$

Wherein, RMS is the least, and the polarization beam splitting of optical grating construction is the most obvious；

Step 3: the design of Structural Parameters of polarization beam apparatus based on metal grating:

At centre wavelength 800nm, go out this optimal structural parameters based on metal grating beam splitter by numerical simulation of optimum As follows: the thickness D of cover layer₁For 225nm, dutycycle f of optical grating construction is 0.21, and groove depth D2 of grating groove is 300nm, light The screen periods T of grid structure is 180nm, and the angle of incidence of light is 0 °；

Step 4: diffraction efficiency and extinction ratio to the optical grating construction in step 3 are analyzed:

As follows by the diffraction efficiency of the optical grating construction in simulative optimization, step 3 and the analysis result of extinction ratio, incident wavelength exists During 702-909nm change, the TM absorbance of optical grating construction and TE reflectance are more than 95%, and incident wavelength changes at 764-855nm Time, the TM reflectance of optical grating construction and TE absorbance are less than 1%；Incident wavelength when 747-854nm changes, optical grating construction anti- Penetrating extinction ratio and be more than 20dB, incident wavelength is when 700-900nm changes, and the transmission extinction ratio of optical grating construction is more than 27.4dB；Enter Firing angle is when changing for-30.3 ° to 30.3 °, and the TM absorbance of optical grating construction and TE reflectance are more than 95%, and angle of incidence arrives at-27 ° During 27 ° of changes, TM reflectance and the TE absorbance of optical grating construction are respectively less than 1%；Angle of incidence-27 ° to 27 ° change time, grating The reflected extinction ratio of structure is all higher than 20dB, and angle of incidence is when changing for-35 ° to 35 °, and the extinction ratio of optical grating construction is all higher than 29.2dB, when light vertical incidence, transmission and the reflected extinction ratio of optical grating construction are respectively 29.2dB and 39.5dB, according to upper State analysis result can be derived that, the TM absorbance of optical grating construction and the work more than 95% of the TE reflectance in 0 order diffraction level time Bandwidth reaches 207nm, and the angle excursion of the transmission of optical grating construction and reflected extinction ratio both greater than 20dB reaches 54 °, meets Wide spectrum, wide viewing angle, the design requirement of High Extinction Ratio；

Step 5: process allowance analysis:

Due to control accuracy and the impact of micro-processing technology, the groove depth of grating groove, the thickness of cover layer and screen periods are in system Have error during Bei, and angle of incidence change all can produce impact to the polarization effect of invention；When fixing other parameters, Cover layer is at 150-300nm, and when groove depth changes between 275-350nm, transmission extinction ratio is both greater than 25dB；When cover layer exists 217-242nm, when grating groove deep changes between 259-315nm, reflected extinction ratio is both greater than 30dB；Light when optical grating construction Grid groove deep is when 259-315nm or cover layer thickness change between 217-242nm, and this optical grating construction is to grating groove Groove depth and cover layer are respectively provided with process allowance；When the angle of incidence of light wave changes between-30 ° to 30 °, screen periods exists Time between 50-187nm, the transmission extinction ratio of optical grating construction is all higher than 30dB；When screen periods is between 114-315nm, grating The reflected extinction ratio of structure is all higher than 30dB；When light wave angle of incidence-30 ° to 30 ° or screen periods 114-187nm it Between change time, optical grating construction is relatively large to the process allowance of angle of incidence and screen periods, screen periods, grating groove deep and cover The thickness of epiphragma layer has technique to prepare tolerance, it is possible to reduce the impact on polarization effect of the error in reality preparation.