TWI291550B - Device for measuring micro-wavelength variation and the method thereof - Google Patents

Abstract

The present invention relates to a device for measuring micro-wavelength variation and the method thereof, both of which utilize the optical activity of a chiral crystal and common-path heterodyne interference technique to propose an optical interferometer for measuring micro-wavelength variation. When an optical heterodyne source passes through a chiral crystal, the optical activity thereof may vary along with the change of the wavelength; the heterodyne interference technique may then be used to measure the phase change caused by the rotation angle, and the variation of the wavelength may then be inferred. The present invention is applicable not only to the measurement of micro-wavelength variation but also to the measurement of macro-wavelength variation; in addition, it has a relatively simple structure and can be operated easily in a real time manner with high sensitivity.

Description

1291550 IX. Description of the invention: [Technical field to which the invention pertains] The present invention relates to a method for measuring a micro-wavelength variation measuring device, and in particular, relating to an optical embryo and silk material interference using a palm-shaped Uhimi crystal. Technology for small wavelength change measuring devices and measuring methods. [Prior Art] The technology of photoelectric precision measurement is extremely extensive in terms of principle, technology, and related fields. The development of (4) is also changing with each passing day. In recent years, the measurement methods of optical interferometers or optical gratings often use small wavelength changes as a means of measurement. Because it can provide a simple_construction and high-accuracy measurement results, it has been widely used. In many different fields, such as: gas flow detection, mechanical disturbance sensing, pressure sensing, absolute distance Lilin' and fine in atomic physics. Since the resolution of this age is closely related to the change of tiny wavelengths, how to accurately measure the change of small wavelengths will help to improve the resolution and sensitivity of the measurement of the system. At present, the technology for measuring small wavelength variations can be divided into two types: domain (4) and interferometer architecture. Both types of architectures have their application and usage restrictions. The main purpose of the diffraction architecture is to use the principle of grating diffraction to diffract light of different wavelengths to different positions and receive it through a charge coupled device (CCD) array to achieve the purpose of light wave dispersion, and then monitor the change of light wavelength. In general, the wavelength variation that can be resolved by the diffraction architecture is about 0.5 nm, and the grating spacing used is about 1 ;; however, to increase the wavelength variation of 5 1291550 resolution, the grating must be The pitch becomes smaller. In another type of interferometer architecture, most of the Fab-time interferometers are used for the analysis of wavelength changes. This is to change the distance to make a long analysis. Recently, Qian You Flavin, ^/. (NK Berger, B. Levit, A. Bekker, and B. Fischer) * is reduced to 0. surgery nm; money 'because this technology is combined with interferometer and diffraction grating, Therefore, the operation of the speculative system is more complicated than that of the general system. Ga C. ^ 36' (2_ 1189.) proposes a measurement technique combining the McKinson interferometer and the Bragg diffraction optical thumb. The difference of the # interferometer is 1. ^ When, about the change in the length of the check

In view of the above, the present invention utilizes the optical activity characteristics of chiral crystals and the conjugated heterodyne interference technique to propose a micro wavelength variation measuring device and method thereof. SUMMARY OF THE INVENTION An object of the present invention is to provide a micro wavelength variation measuring apparatus and method thereof, which are capable of effectively detecting a small wavelength by a simple architecture of an optical interferometer by using a hetero-crystal and a common-light interference interfering technique. The amount of change. Another object of the present invention is to provide a micro pain length change measuring apparatus and method thereof, which have the advantages of simple structure, easy operation, immediate, rapid, avoidance of external environmental disturbance effects, and high sensitivity. Still another object of the present invention is to provide a micro wavelength variation measuring apparatus and method thereof which are operable to measure a change in a large wavelength. The invention provides a micro-wavelength variation measuring device, which comprises a heterodyne light source, which is a 61291550 laser light source and can be incident on a quarter-wave plate in a test module to generate an optically smoothing heterodyne light source. And incident on a pair of palm crystals, when the optical heterodyne source is incident on the palm crystal, its optical activity will change with the wavelength of the laser source, and a calculation device can be used according to the test mode. The phase change amount generated by the group is calculated to obtain the wavelength change amount of the laser light source. The present invention further provides a method for measuring a small wavelength change, which first provides a heterodyne light source, which is a laser light source, and the difference light source emits a horizontal level. The light having an angular frequency difference between the polarized light and the vertical polarized light causes the heterodyne light source to be incident on a quarter-wave plate through at least one optical path to generate an optical heterodyne light source, and is incident on a pair of palm crystals to utilize the same The optical activity produces a phase change amount of the rotation angle as the wavelength of the laser light source changes; finally, the wavelength change amount of the laser light source is calculated based on the phase change amount. The purpose, technical contents, features and effects achieved by the present invention will become more apparent from the detailed description of the embodiments and the accompanying drawings. [Embodiment] The small wavelength change measuring device of the present invention includes a heterodyne light source 10' which emits horizontally polarized light without angular frequency difference between straight polarized lights; a test module 2 is mainly used - four The wave plate 205 converts the heterodyne light source into an optical heterodyne light source, and utilizes the optical characteristics of the pair of palm crystals 201 to cause the optically heterodyne light source incident on the palm crystal 2() 1 to follow. The laser wave sings the amount of change of the line to the sway; finally, the _ calculating device % calculates the amount of change caused by the test module 20, and uses the heterodyne interference technique to measure the phase change caused by the rotation angle, and performs the derivation calculation. The amount of change in the laser wavelength can be determined. This part is the main spirit and architecture of the 7 1291550 of the present invention. The following is a detailed description of the principles and architectural processes. First, before fully describing the small wavelength change measuring device and measuring method, the phase change and principle generated by the light generated by the optical heterodyne light source through the palm crystal are explained in detail: § A heterodyne light source with a wavelength of /1 After passing through the palm-shaped crystal with thickness j, the phase difference between left-handed and right-handed light can be expressed as formula G):

Wherein, the domains are respectively expressed as the wavenumbers of the right-handed and left-handed lights, and β is the rotation angle of the circularly polarized light passing through the palm-shaped crystal; for the general rotation angle of the unit length of the palm-shaped crystal and The wavelength of the source; the dispersion relationship between i can be written as shown in equation (2): Qing (a) ¥1^ stomach 4, (2) where n, j, a and y are the resonance model parameters associated with the palm crystal; Substituting into equation (1), the phase difference produced by equation (3) is as shown in equation (3).

2-2-%)2 4(^2+4) - μ2 - (3) From the equation (3), the function of the phase difference rib wavelength j is known. Therefore, when there is a slight change in wavelength △, the phase difference will also produce a slight change and the relationship between ΔΑ and f can be written as equation (4): MS! spider, (4) Therefore, when the fresh crystal _ optical rotation angle is affected by the light source When the amount of change in the phase difference is caused by the influence of the wave surface, the ΔΑ value of the wavelength change can be transferred from the equations (3) and (4). i 8 1291550 Since the heterodyne light source emits light having an angular frequency difference between the left-handed polarized light and the right-handed polarized light through a quarter-wave plate and passes through the palm-shaped crystal, the amount of change in the phase difference does occur, and thus the present invention The amount of wavelength change can be obtained by this characteristic.

Referring to the first figure, the light source used in the present invention is a heterodyne light source (especially) 10 which is still between the horizontal (/>-) and the vertical (5~) polarized light, wherein the difference light source is further The 10 series includes an adjustable laser light 101 that emits a linearly polarized laser source, and a function generator 1〇2 generates a waveform function signal, which is then amplified by a linear voltage amplifier 1〇3. Thereafter, the signal passing through the function generator 1〇2 and the linear voltage amplifier 1〇3 is modulated by an electro-optical crystal modulator 104 to emit a heterodyne light source having an angular frequency difference. When the difference light source 1 passes through the beam splitter 202 in the beam splitter test module 20, it is split into two beams: a reflected beam and a penetrating beam, each of which has an optical path. Wherein, the reflected beam first passes through the transmission axis and the X-axis clamp 45. After the first analyzer 203 enters the first photodetector 204, the J〇nes vector of the light reaching the first photodetector 204 can be expressed as:

Er=ANr(45°)-BS-Ein ifl lYe -W2 2(1 l person 〇 em Ίϊ

f cos V cot T

Among them, 仏 is the outer wire __ vector, the age of money is secret, and (6) is the phase difference caused by the light reflected by the BS. Therefore, on the first photodetector 204, the measured form of light intensity can be expressed as equation (6): 2 1 eight = | five r | = ^ [1 + COS ( slave one D], 9 (6 1291550 where /r is the reference signal. On the other hand, the penetrating beam passes through the fast axis and the x-axis, and the first quarter-wave plate 205 becomes the optical heterodyne source. After the length of j is opposite to the palm crystal 2〇1, and passes through the fast axis and the X-axis clip 135. The second quarter-wave plate 206, the Jones vector at this time can be expressed as equation (7): = Ίι

Icoi / 2-ikrd

e-iGM/2~iklCi (7)

5 2 = V2 (Λίωί/2-2ί^+ΐφΜ -ΐωί/2-2ΐ^(ί+ίφΜ Ll〇J

Then, the electric field name is vertically reflected by the high reflectance mirror 207, and then returns through the original path, sequentially passing through the second quarter wave plate 206, the palm crystal 2〇1, and the first quarter wave plate. After 205, the electric field form can be expressed as equation (8): (8) where 'the phase difference caused by the reflection of the light reflectance mirror 207. Thereafter, the light is reflected by the beam splitter 202 and passed through the transmission axis and the X-axis clamp 45. The second analyzer 208 is finally re-entered into the second photodetector 209, and the Jones vector of the light reaching the second photodetector can be written as (9).

Ef = ^Ι2-ΐ2Κά+ΐφΚί-ΐφΒ5Ι2 敁/2-/2 state "/2 Therefore, the test signal /^ measured on the second photodetector 209 can be expressed as a formula (1〇): Λι =|^/| =-[l + cos(^ + ^/-^)], (10) where the circularly polarized light of the optical/difference heterodyne source passes through and is reflected after the palm crystal 201 The phase difference, which can be expressed as Equation (11): (11) 1291550 According to Equation (6) and Equation (1G), the reference signal; ^ test signal /u is simultaneously input to the lock-in amplifier 301 in the computing device 30. The phase difference i value introduced by the light through the palm crystal 2〇ι can be obtained. On the second marriage amount, the wavelength of the laser light is changed, and the test signal /t2 at this time can be expressed as a formula ( 12): hi =^ + oos(ωt + φ,2-φBS)]. ((2) where 〆2 can be solved by the same method as above. Therefore, the measured phase difference variation △ "= 2 △ In the substitution type (4), the amount of change of the small wavelength Δ乂 can be obtained. The entire calculation process is to measure the phase change amount by the common path heterodyne interference technique. After explaining the technical features and principles of the present invention. In order to verify the feasibility of the present invention, it is specifically tested with the wire. In the experimental test, the inverted palm crystal of the present invention is 10 cm (mm) thick Bu2Ge〇2 () (BGO) to measure the thunder. The wavelength of the source is changed from 632·6 nm to 633·6 nm, and the initial wavelength is 633·! nm. The parameters of the correlation resonance model in the dispersion relationship between the unit length rotation angle and the source wavelength are respectively &;=1853 _ TM βΤΆ ' Ζ^-0. 00295 deg mm /zm2. c/a=-〇. 7715 deg mm'1 ^ λ/=〇. 4015//m and several ^0.2421 "m. electro-optic crystal The modulator (Model 4〇〇2, NewFocus, Inc.) is produced as a function of a 1 kHz tin-toothed wave and a half-wave voltage of 125 |. | Lake, a phase-locked amplifier with a resolution of 0.001 (Model SR-850) Stanford Research System) measures the phase difference and also uses a personal computer to record and analyze the values. The results of the experiment are shown in the second figure, and the second figure shows the relationship between the amount of change in phase difference and the amount of change in wavelength ΔΛ. In order to be able to taste with the laser reading value, the present invention compares the reading value of the laser output wave with the measured value Δ The time tree will be on the same ~ sheet, and the result will be the third. The □ and 1291550 knives marked on the third chart are not the reading values and measured values of the laser output wavelength. It can be clearly seen from the third figure. It can be seen that there is a very rhyme correspondence between the measured value ΔΑ and the Thunder mosquito length_ value. Since the dispersion of the palmity (10) is reduced, the dispersion can be made to be continuous and has a large variation range. This can make the formula of the wavelength variation larger in the present invention. However, when the range of the butterfly in the wavelength gamma becomes larger, the modulation voltage will be different for the electro-optic crystal modulation (4), so the polarity of the polarized light will be affected, which may cause mismatch in the system;

Overcoming each problem 'The invention can be added to the frame towel of the first figure _ feedback control woven set design juice'. See the fourth figure, a lock reducer 3〇1 is still based on the test signal The phase difference variation is obtained from the reference signal; the feedback control device network includes an oscilloscope and a computer 3〇2 'Electric Moon|302 is connected to the heterodyne source 1〇 and the lock-in amplifier 3〇1, and the oscilloscope The difference signal of the first optical debt detector can be detected, and the heterodyne light source 1G and the lock-in amplifier can be adjusted accordingly. The fifth graph shows the experimentally measured half-wave voltage versus source wavelength, so that the relationship can be used to obtain more accurate measurements. In addition, it has been experimentally verified that the field does not change the half-wave voltage, and the measured wavelength has very accurate results within 2 nm of the central wavelength. In the present invention, the error of the lock-in amplifier, the polarization mixing error and the polarization rotation error will affect the accuracy of the phase measurement. Considering these error factors, the total phase error of the experiment is about s〇.〇3°; Then, from the experimental results of the second graph, when the wavelength change amount Δ; ι is i ,, the phase difference changes by 3.696. . Substituting the above values into equation (13): The error of the wavelength variation can be calculated as $Δ rr. From the calculated result, A can be obtained; Urrs〇e 00812 nm. 12 1291550 Furthermore, another feature of the present invention is that a any-coherent light source can be used as the test light source without having to know the recording in advance to correct the dispersion. The light source of the same wavelength is not clear for the optical activity of the palm crystal, and its ability to rotate the palm crystal __ will be different; the sixth graph is the relationship between the optical rotation angle of BG0 and the wavelength. As can be seen from the results of the graph, for a short-wavelength light source, the rotation angle of the palm crystal has a large rotation ability, and thus the amount of change in the phase difference is also large, so

There is a higher sensitivity in quantity. For example, at a wavelength of 532 (10), the sensitivity of the wavelength change is about 0.0023 nm. In summary, the present invention utilizes the optical activity characteristics of the palm crystal, and proposes an optical interferometer architecture to detect the variation of minute wavelengths. The invention also uses the common optical path heterodyne interference technology to measure the phase change, and uses the computing device to calculate the variation of the wavelength. According to the above, the invention has the advantages of simple structure, easy operation, instant, fast and avoidance. The outer ring (four) dynamic influence and high-recording gamma can also be operated on the measurement of a wide range of wavelength changes. The embodiments described above are merely illustrative of the technical spirit and characteristics of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the contents of the present invention and to implement them. Equivalent changes or modifications made by the spirit of the present invention should still be included in the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The first figure is a schematic diagram of an embodiment of an embodiment of a small wavelength change measuring device of the present invention. The second graph is a graph showing the relationship between the amount of change in phase difference and the amount of change in wavelength of the present invention. 13 1291550 The first figure is a graph showing the relationship between the read value of the laser input wavelength and the measured value Δ彳 of the present invention. The fourth figure is a schematic diagram of the architecture of the wavelength change measuring device cap being added back to the control relay in the present invention. The fifth picture is the experimentally measured _ half-wave and the wavelength of the system. The sixth graph is a plot of optical rotation angle versus wavelength. [Main component symbol description]

1〇heterodyne light source 101 adjustable laser light 102 function generator 103 linear voltage amplifier 1〇4 electro-optic crystal modulator 20 test module 201 to palm crystal M2 beam splitter 203 first analyzer plate 2〇4 first light detection 205 first quarter wave plate 206 second quarter wave plate 207 high reflectivity mirror 208 second analyzer 209 second photodetector 30 computing device 301 lock-in amplifier 302 computer 303 Feedback control device 3〇4 oscilloscope

Claims (1)

1291550 X. Patent application scope: A small oil; long change measuring device, comprising: a heterodyne light source, which is a laser light source; a test module, which has a pair of palm crystals, the heterodyne light originally Converting into an optically-polarized heterodyne light source, incident on the pair of palm crystals, the optical activity of which varies with the wavelength of the laser source to produce a change in the rotation angle; and a computing device for calculating the value, and according to the The amount of change generated by the test module takes the amount of wavelength change of the laser source. 2. The micro wavelength variation measuring apparatus according to claim 1, wherein the heterodyne light source emits light having an angular frequency difference between the horizontal polarized light and the vertical polarized light. 3. The device of claim 1, wherein the heterodyne source comprises: an adjustable laser beam that emits a linearly polarized laser source; and a function generator that generates a waveform function signal; a linear voltage amplifier that voltage-amplifies the waveform function signal; and an electro-optic crystal modulator that modulates the signal according to the function generator and the linear voltage amplifier to emit the heterodyne light source. 4. The device of claim 10, wherein the test module further comprises a beam splitter that splits the incident heterodyne light source into reflected light and transmitted light; the reflected light first penetrates A first analyzer enters a first photodetector to cause the first photodetector to detect a reference signal; and the transmitted light is converted into an optical heterodyne source by a first quarter wave plate After the incident to the 15 ! 29155 〇 for the palm crystal 're- _ the second quarter - wave plate and - high reflectivity mirror reflection, then through the second quarter - wave plate, the After the palm crystal, the first minute-wave plate is reflected by the wire, the second detecting plate is irradiated to the second wire to measure a test signal to receive the different device. The amount of change in the phase difference between the reference signal from the first and second photodetectors and the rotation angle generated by the wavelength change of the test signal is calculated, thereby calculating the wavelength variation of the laser source. . 5. The micro wavelength change measuring device according to item 4 of the patent application, wherein the first quarter spring wave plate is set at a position where the fast axis and the horizontal direction are sandwiched by 45 degrees. 6. The device of claim 4, wherein the second quarter wave plate is positioned at a position of 135 degrees between the fast axis and the horizontal direction. 7. The small wavelength change measuring device according to claim 4, wherein the phase difference variation is obtained by using a common optical path heterodyne interference technique. 8. The device of claim 4, wherein the computing device further comprises: a lock-in amplifier that determines the phase difference variation based on the test signal and the reference signal; A computer calculates the amount of wavelength change of the laser light source based on the amount of change in the phase difference. 9. The device of claim 4, wherein the computing device further comprises: a lock-in amplifier that determines the phase difference variation based on the test signal and the reference signal; 1291550 - The feedback control weaving 'the money touches the external difference system and the lock-in amplifier, the feedback control device can detect the difference signal outside the light-thin light m, and according to this (4) heterodyne light source and phase lock Rose. 10. The micro-wavelength change measuring device according to the ninth aspect of the patent, wherein the feedback control splitting further comprises an oscilloscope> (measuring the difference signal of the first-thinner, & And a computer for performing all the arithmetic processing. U. The small wavelength change measuring device according to claim 8 or 9, wherein the relationship between the phase difference variation and the _wavelength variation is: AA = idx Αφ ° 12, a method for measuring a small wavelength change, comprising the steps of: providing a heterodyne light source, which is a laser light source; and injecting the heterodyne light source into a quarter wave via at least one optical path An optically vibrating heterodyne source is generated after the sheet is incident on a pair of palm crystals, and the optical activity of the palm crystal is varied according to the wavelength of the laser source; and the amount of change is calculated to The wavelength change amount of the laser light source is obtained. 13. The method for measuring a small wavelength change according to claim 12, wherein the heterodyne light source emits light having an angular frequency difference between the horizontal polarized light and the vertical polarized light. 4. The method for measuring a small wavelength change according to claim 12, wherein the heterodyne light source is further divided by a beam splitter to be divided into two optical paths of reflected light and transmitted light; the reflected light first penetrates A first analyzer enters a first light <detector to cause the first light extractor to detect a reference signal; and the transmitted light is converted into an optical rotation by a first quarter wave plate After a poor light source, it is incident on 17