Virtual lab basic experiment tutorial -7 Polarization (1)

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Preface

This is the seventh collective work of Dachuang team , Basic experiments for physical optics – The phenomenon of polarization has been explored and tried . There are many experiments that are easy to operate in the field of polarization , This article only introduces the basic experiment .

One 、 Introduction to polarization and polarization

1、 classification ：

According to the polarization characteristics , Light waves can be divided into natural light 、 Partially polarized light 、 Line polarized light 、 Circularly polarized light and elliptically polarized light 5 Kind of .
1. Line polarized light
In the transmission of light , It contains only one kind of vibration , Its vibration direction is always kept in the same plane , This light is called linearly polarized light （ Or plane polarized light ).
2. Partially polarized light
Light waves contain transverse vibrations in all possible directions , But the amplitude varies in different directions , The amplitude has maximum and minimum values in two mutually perpendicular directions , This light is called partially polarized light . Natural light and partially polarized light are actually composed of many linearly polarized light with different vibration directions .
3. Elliptically polarized light
In the transmission of light , The electric vector of each point in space rotates with the light as the axis , And the endpoint of the electric vector traces an elliptical trajectory , This light is called elliptically polarized light . Look in the direction of the light , Any clockwise rotation of electric vector is called right-handed elliptically polarized light , Those rotating counterclockwise are called left-handed elliptically polarized light . The rotating electric vector in elliptically polarized light is composed of two identical frequencies 、 The vibration directions are perpendicular to each other 、 The result of electric vector vibration synthesis with fixed phase difference
4. Circularly polarized light
The light that rotates the endpoint of the electric vector to trace a circular track is called circularly polarized light , It is a special case of elliptically polarized light . After averaging in our observation period , Circularly polarized light looks like natural light . But the polarization direction of circularly polarized light changes according to a certain law , The polarization direction of natural light changes randomly , There are no rules .

2、 The generation method ：

There are four ways to obtain linearly polarized light from natural light ：

1. Using reflection and refraction .
2. Using dichroism .
3. Using the birefringence of crystal .
4. Use scattering .
   in addition , Linearly polarized light can pass through the wave chip to produce circularly polarized light and elliptically polarized light .

Two 、Virtualab Simulation

1、 Build a light path

（1） Linear polarization to circular polarization

First, drag a plane wave into the new panel

Set the parameters of plane wave , In polarization polarization（ It is also the first time to set the polarization mode in the light source ） Select line polarization , And set to 45 degree .

Other basic parameters are default .
Then drag in a wave plate （ Phase retarder ）, Find... In the library Retarder( Phase retarder , It can cause a relative phase delay between two mutually perpendicular linear polarized lights of polarized light , So as to change the polarization state of light )

Double click to set parameters , This construction needs to convert linear polarization into circular polarization , So in physical parameters Set in the for 1/4 wave plate , Its Jones matrix will automatically change .

Other parameters default
After that, in order to compare the light before and after the wave plate, we put one before and after the wave plate Raw Data detector

Double click to set parameters （ Two detectors are set at the same time ）
In the detector function Detector Function The admission Use Cubic Interpolation, Other default .

After the construction is completed, choose field tracking ：

After getting two images, you need to click the oval arrow icon in the window （ Paperclip pattern ）

You can get the following figure , Incident light is linearly polarized , The outgoing light is circularly polarized .


In order to clearly see the polarization direction of light, click the icon in the lower right corner and open the interface to select show arrows.


You can get . The outgoing light is left-handed circularly polarized .（ Left hand rotation is black , Right hand rotation is blue ）

（2） Right circular polarization to left circular polarization

To realize the conversion from right-handed circular polarization to left-handed circular polarization, only change the parameters of the light source and wave plate , In the plane wave polarization Select circular polarization .

And set it to right rotation .

In addition, it is necessary to select the full wave plate by modulating the phase retarder and set the phase delay to -π.

Follow up the track again and get , The former is the initial right-handed circular polarization , The latter is left-handed circularly polarized light after passing through the half wave plate .

2、 If not raw data detector

If we are familiar with camera detector, We can also find a way to check our final polarization direction . But pay attention here , The polarization direction can be checked only after entering the data view state of harmonic field . The paperclip like Mark will appear in the menu bar above .

But in the process of transforming the field detected by the original detector to the array state and then to the harmonic field , There is no really preserved polarization information , It can be noted that in the process of transforming from array state to harmonic field , The pop-up window will let you default to a Jones vector .

In this way, the polarization information of the original field will be lost , So we use raw data detector It's very necessary .

3、 About using generic patterns

Note that the radian value of phase delay is set here , The settings are Jyy As the specific position of a vector rotating around the origin , When we set -3.1416rad when ,Jyy It turns counter clockwise pi Phases , from 1 Change to -1
$$\left[\begin{array}{cc}1& 0\\ 0& -1\end{array}\right]\text{\hspace{1em}(4)}$$
Jones matrix corresponding to half wave plate . The settings are shown in the figure 1.5707rad(pi/2) when , It turns clockwise 90°, from 1 Change to -i.

4、 introduce polarizer

We can use polarizer to realize a pair 45° Acquisition of linearly polarized waves , At this time, a new one can be pulled out plane wave（ The default linear polarization direction is 0°）.

Set directly to 45°.（ What this component generates is linear polarization , Of course, you can set linear polarization at various angles ）

Simulation results .

We convert these two graphs into numerical models （ The transformation method will not be repeated here ）, Study the change of light intensity .


It can be seen that the change of light intensity is basically $E^{\prime }=E_{0}cos\theta =E_0\ast cos45°$

3、 ... and 、7.6.1.18 The operation difference of version

stay Raw Data Detector There is no need to set the interpolation method .

Four 、 Effect supplement

We have retarder By default, it will be set to y The shaft is in the form of a fast shaft （ This is also the beginning of our linear polarization set to 45° form , So our experiment in light path construction , That is, the linearly polarized light passes through a fast axis and forms a 45° Quarter wave plate ）

obviously , To produce elliptically polarized light , This angle is not 45°, Here we can rotate this wave plate , Note that the independent position of the wave plate should also be operated here . We rotate clockwise 15°.

Finally, the following simulation results are obtained .

If you rotate again 45°, The fast axis will coincide with the incident light , Ray polarization .

If you rotate again 90°, The fast axis will again be polarized with the incoming ray 45°, Emitting circularly polarized light （ Right hand ）.

summary

This article is written by members of Da Chuang team ： Tang Yiheng 、 Help Yang Yu 、 Huang Yinuo 、 Li Sitong 、 Ming Yue jointly completed .
This article is only the basic part of the polarization experiment , This article focuses on the study of wave plates , More interesting fields such as birefringence will be further covered later .
This article adopts the trial version and 7.6.1.18 Version for experiment and demonstration , Enhanced applicability .