声光调制器、声光移频器、声光偏转器使用手册.pdf声光调制器、声光移频器、声光偏转器使用手册。包含国

文件名称: 声光调制器、声光移频器、声光偏转器使用手册.pdf

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详细说明：声光调制器、声光移频器、声光偏转器使用手册。包含国外相应型号的原理、结构、使用方法。IMPORTANT This operating manual is related to most of our products with Isotropic interaction This includes Ao Modulators frequency shifters and low resolution deflectors To know its specific characteristics (positioning, polarization, optical aperture, performance), please refer to the information and test sheet of your modulator. This operating manual has been written in order to help for the installation of your Ao component. Read this manual entirely before using and keep it nearby you when using the Ao component Please read the Erreur! Source du renvoi introuvable. (page 4) before beginning the Erreur Source du renvoi introuvable. part (page Erreur! Signet non defini. to 7. If you meet some difficulties with the installation of your AO component, please refer to the Frequently Asked Questions (page 9). For any question about the Acousto-Optic definitions or general purpose, refer to the last part, Erreur Source du renvoi introuvable. (page 10) Thank you for the confidence in A&A Opto-Electronic Hope to see you soon on our web pages www.aaoptoelectronic.com Please do not hesitate to contact A&A for further information AA Opto-Electronic Division Customers' service Tel:+33(0)176915012 FaX+33(0)176915031 E-mail: sales(a-a. fr GENERAL PRECAUTIONS Mechanical Precautions Note that any strong mechanical shock can lead to irreversible damage on the component and particularly on the crystal lono for the products with fixation from the bottom part: take care with the length of the screws. too g screws may destroy the crystal Electrical Precautions v Do not force on the connectors v Never disconnect the connectors while power supply iS ON Optical Precautions Windows Cleaning v Dust on optical windows can be responsible for irreversible damage on the coating(especially if you use high power ). Use the component in a clean environment as much as possible v To clean up the optical surfaces: use a soft Q-tip. First, clean it with pure ethanol, then with acetone. Most of Ao components use soft materials and need careful cleaning v Oily stains"should be removed immediately to avoid irreversible marks Installation and Adjustment precautions All of these specifications values are indicated on the test sheet of your ao component Please refer to it Laser Power Density v Check the maximum value specified for the given AO component, otherwise irreversible damage could occur Laser polarization Y Make sure that the specified optical polarization is correct to have an optimum Ao efficiency (random, circular, perpendicular or parallel to the base - depending on the component) Optical Aperture Y Holes in the housing of the modulator are larger than the specified optical aperture. The Ao component will need to be adjusted, using slight translations perpendicular to the laser beam, ir order to get the beam traveling through the correct area of the crystal and to maximize the fici focus the laser beam on the ao cover Incidence Angle v Make sure that the position of the Ao component corresponds to the specified value of the ncidence angle in order to optimize the efficiency Warning: Any disassembling of your AO component makes the guarantee null and void! AO PRESENTATION Laser beam passing through an acousto-optic modulator, driven by an RF power, is diffracted into a single power. For low RF power, the diffracted laser intensity is proportional to the Radio Frequency powe/ 3 order(). Under a specific incidence angle(bragg) the diffracted laser beam intensity can be controlled by the RF I Each time we will speak about Modulator, you can replace by Frequency Shifter or Lowe resolution Deflector (): This interaction can be possible if several parameters are respected(Bragg interaction) SYNOPTIC OF THE MODULATION SYSTEM Laser Modulator 40 a Order Modulator Incident Beam Modulation RF Driver Power source(s) Ao connected to the driver(Drive re power: voltage control DESCRIPTION OF THE MODULATOR The principal elements of your AO component are represented in the drawing below 1- Cover ( 2-Optical aperture 3-RF connector 4-Fixation hole(threaded hole) 5- Bragg hole(cleared hole) Refer to the Interface ()of your component) 6- Base plate (*) on the back of the test shee MECHANICAL DRAWING Each product may have a different mechanical drawing which can be provided by AA. This mechanical drawing states with accuracy the outer dimensions, the fixation holes and the optical axis TO START OPERATION It is recommended to operate the AA Modulator with its associated AA RF driver, which is optimized at factory to get the highest performance you're your Ao component Please refer to the ao test sheet to know the maximum rF power you need to operate your device For the first installation, remove the protective tape on the two apertures(in oUt)of the Ao cover(O). IN and OUT are specified on the faces, when it has an importance and consequence on the performances of the component For your safety and the safety of your modulator, do not install the modulator while the LaSER is oN. Use a mechanical shutter or switch off your laser during this procedure, especially for high power lasers Now, you are ready to begin the installation of your Ao component OPERATION WHAT DO YOU DO? COMMENTS Install the Ao component, so that the laser o Make sure the laser beam diameter is /ower than the beam enters trough the IN face and by the optical given active aperture of the AO component, and its power aperture ()at its centre under the incidence lower than the maximum power tolerated by the AO angle component 丿 ypically: Beam Diameter≤0.7 X Active Aperture To find quickly the optimal incidence angle, install the Fig. 1: Observations of the 0 order bear AO component near the auto-collimation (the reflexion on a black screen does not pass inside the laser cavity but just close). Then Laser 532nm through an MT 110 turn the Ao component to the incidence angle value indicated on the test sheet of your AO component. Sight rotations Screw the Ao component by using the fixation 7 If you fix your AO component you will have less hoes(④) difficulties to proceed the following steps, and your product 2 wi∥ be "protected"and‘ secured o Watch out for the screws length. Please refer to the test sheet to get the maximum authorized length. Screws -ixation holes that would be too long could damage the crystal Check that the input laser polarization is a wrong input polarization will decrease the performances of the Ao components, and will lead to conform to the base plate( 6) 0 Order unexpected effects. Please refer to the test sheet of your component. 3 Incident巳ea Connect the RF Output of your driver to the " RF 4Connector"(3)of the Ao component with the provided RF cable Connect the RF Input of your driver to the contro 5 source (Signal generator, Power supply,PC B Switch the rf driver on Make sure that the delivered RF modulation output atible with the Ao component (frequ o When the RF signal is applied to the AO component, the laser is diffracted as shown in Fig3 o Please note that in some cases (depending on your 6 Fig. 2: Diffraction of the laser beam through the Ao component component) you can see several diffraction orders, but their intensity remains weaker than the first order. The angular sketch depends on your AO component. The first 2Order .Order 0 Order /" Order order can also be positive or negative. Please note that in order to give general information, we never precise a sign for the first order in this manual Fig 3: Observation on a screen of the diffraction a /t doesnt correspond with your observation? with a 532nm laser for a MT 110 k Please refer to the Erreur source du renvoi introuvable. part (page Erreur Signet non defin.) ADJUSTMENT OPTIMZATION Acousto-Optic Efficiency ADUSTING POSITION OF THE AO DEVICE The aim of this adjustment is to optimize the position of the Ao component, by measuring the level of the output optical signal. It requires the following components of measurement: photo-detector connected to an oscilloscope o Install a photo-detector on the"diffraction order (")of the laser beam 2 Connect the photo-detector with an oscilloscope. Check the level indicator on the oscilloscope corresponding to the received laser intensity, stays in the linear part of the photo-detector. 3 Adjust the input laser incidence angle with a slight rotation of the Ao component to get the maximum intensity in the 1 diffraction order Adjustments can be done by hand, thanks to rotation-translation stages, or thanks to the bragg hole() for higher accuracy This rotation can be positive or negative depending on the mode/ and on the shifted frequency Please refer to the test sheet of your Ao component to get this specification 4 Optimize the efficiency in the 1 diffraction order at the end in associating slight translations and rotations of the ao component light rotations INPUT POLARIZATION The aim of this adjustment is to optimize the laser polarization, by measuring the level of the output optical signal in First order. It requires the following measurement system: photo-detector connected to an oscilloscope o Install a photo-detector on the"1 diffraction order ()of the laser beam 2 Connect the photo-detector with an oscilloscope. Check the level indicator on the oscilloscope, corresponding to the received laser intensity, stays in the linear part of the photo-detector 3 Adjust the laser polarization with slight rotation of the laser to get the maximum intensity in the diffraction order RF POWER If an increasing RF signal power allows a better efficiency, but when the optimum RF signal value is exceeded, the efficiency decreases, because the conditions for an optimal Acousto-Optic interaction are either not observed 1 order AO Eficiency versus RF Power Maxim um (sat) Optimum F=二===二二二 Acousto-Optic Rise Time OPTICAL SET-UP Incident Modulator Order 1 Order o F F RE To decrease the Ao rise time(tr)of your Ao component, reduce the beam diameter(O): T,=B, with B a constant and v the acoustic velocity Choose the beam diameter to calculate the necessary focal length, use the following relation in function of the F2 desired beam diameter(0): 0 =a L., with a a constant depending on the beam profile(=i for TEMOO beams, in Gaussian diffraction limited approximation) Precaution Calculate the minimum rise time corresponding to the minimum beam diameter specified in the test sheet of your Ao component. In fact, if the beam diameter is too small, the laser beam divergence(DIVo) will be too arge. So there will be an incorrect matching between the laser beam divergence(DIVo) and the acoustic divergence(DIVA), which will lead to an output elliptic beam associated to an Ao efficiency loss ()Where is the s diffraction order?: 1-Switch the RF signal off. 2-Locate the diffracted laser beam(it's the 0 order).3-Switch the RF signal on. 4-Several orders appear. 5-Refer to the test sheet to know the position of the 1 order compared to theo orderat left or at DIFFICULTIES AND PROBLEMS. FAQ You may have some difficulties, while operating your Ao component, to obtain the following diffraction figure 2 Order s Orde 0 Order 1-Order Observation on a screen oi the diffraction with a 532nm laser for a m.110 Please, check at first the different values(incidence angle, polarization, wavelength, frequency control .. indicated on the test sheet of your Ao component To proceed quickly, the following chart identifies some of the most frequently asked questions. We suggest some possible solutions and offer recommended replacement procedures If your problem is not described below or if these explanations do not answer your needs then please contact AA Customers service PROBLEM OBSERVATION POSSIBLE CAUSE AND CORRECTION o Laser Power Supply is not functioning No light at the ao component output o Laser beam does not enter by the in face of the ao component Laser beam output diameter varies o Laser Power is too high. Please refer to the test sheet, to get the maximum value supported by the Ao component o Laser beam does not enter by the in face of the Ao component o The laser polarization is not appropriated to the Ao component Please refer to the test sheet, to know which polarization to use with the AO compone d The current which corresponds to the couple command of Tension Efficiency LOss le sp command of impedance is not appropriated to the product. Check the at the ao values(indicated on your Test Sheet)compare them which the piloting Companent Output D Laser Beam is not centered on the optical aperture Centre the laser compared to the (or the Ao component) along the horizontal and the vertical axis value specified in Truncated spots(top or bottom) the test sheet) o Laser Beam Diameter is too high. The laser beam output is truncated Please refer to the test sheet, to get the maximum value for the ao Truncated spots(top and bottom) componen o The laser beam does not enter the crystal under the appropriate angle Rotate the ao component to place it under the incidence angle specified 2 shining spots on the Test Sheet of your product Very scattered oIly stains"remain on the optical face and the Output Laser Beam is Laser Beam scattered. First, clean up the optical surfaces by using a soft Q-tip with Output cattered an nd diffused spots pure ethanol, then with acetone o The laser beam diameter is too small. Enlarge the laser beam diameter. To know what is the minimum tolerated diameter, please refer Elliptic Laser Beam output the Test Sheet of your AO o The modulation is too fast for the component Decrease the E∥ ptic spots modulation speed. Please refer to the Test sheet to get the exact value. o The current which corresponds to the couple command of Tension command of impedance is not appropriated to the product. Check the values (indicated on your Test Sheet)campare them with the piloting o The laser beam diameter is too small. Increase the laser beam The modulation speed is not sufficient diameter with an expander, for example. To know what is the minimum (as quickly as the one indicated on your Test Sheet) tolerated diameter, please refer to the Test sheet of your Ao component o The detector's response time is longer than the modulation speed Please refer to the characteristics of your sensor to have its rise time o Do not use a T connector. It disturbs the signal (loss, noise.) The deviation angle doesn't correspond with the one o According to the model of the AO component (frequency, which is specified on the Test sheet Rotate the Ao component to obtain the appropriated configuration ?to wavelength. the Acousto-Optic interaction is more or less sensitive the incidence angle between the laser beam and the ao compo (position andor value) TERMINOLOGY PARAMETER DIMENSION DEFINITION Optical Wavelength(air) Incident and Diffracted Crystal Indexes k Optical Incident and Diffracted wave vector K Acoustic /Drive Frequency m/s y RF Drive Power F Drive Voltage (defined by /rms or /pp) V External Control voltage of the RF Driver( vry) A Incident Optical Intensity Oulput Optical Intensi Diffracted Optical Inte it the hOrde D Optical aperture A T AO Rise Time F Hz Modulation Fr Optical transmission AO Efficiency KEY WORD DEFINITION /COMMENTS/ FoRMULA When an acoustic wave propagates in the Bragg cell, it generates a perturbation of the refraction index in the cell. When the matching phase is successful, the light is diffracted through the acoustical"grating"(with a grating step corresponding to the acoustic wavelength): A=- where v: the acoustic velocity and F: the acoustic frequency ACOUSTO-OPTIC INTERACTION the theory of the momentum and energy conservations (for the incident light (k, i), the diffracted light(Ra in) and the ustic signal(K F) allows to obtain the following expressions k,=k+K, with/k; /=2n/2/ka/=2nd/) and/K/=2zF/v For Isotropic Interaction:n=n→/k/=/k/,t=f±F "0"AND"1ST orDERS The 0"and"orders are respectively, the direct beam through the ao component, and the beam deviated by acoustic diffraction grating In the anisotropic interaction, a flip of the incident polarization is produced depending on the difference of the material OUTPUT POLARIZATION refraction index In the isotropic interaction, the output polarization is identical to the incident polarization(ni=nd) The optical transmission is the ratio between the light intensity at the output of the Ao component (o) and the light OPTIC AL TRANSMISSIONT) intensity of the incident laser beam (lop): T 210c The carrier frequency allows to drive the ao component. To generate an ao interaction, the following relation must be CARRIER FREQUENCY(Fc) 2v× sIn LE respected: Fc DRIVE POWER (PRF) The drive power is the electrical power delivered by the rF driver and sent to the Ao component to drive the light outpu tensity The Ao efficiency is the ratio between the intensity in the 1 diffracted order(I1) and in the order(I, ACOUSTO-OPTIC EFFICIENCY n2(√ PRE I with c: a constant ACCESS TIME (TA) The access time is the time for the acoustic wave to cross the optical aperture(D)of the Ao component: T ACOUSTIC POWER (P) The acoustic power is proportional to the rF drive power: P=ax Pf, with(a< 1)a transformation factor The Ao rise time is the time for the Ao efficiency to increase from 10% to 90% AO RISE TIME( TR) Tr=0. 66D with D: the beam diameter 1/(by considering a pulse drive signal and a Gaussian laser beam, 0.48 MODULATION FREQUENCY(F) Naturally linked to rise time: Fre

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