Faraday Isolator - Newport Corporation
Contents
1. isolation direction the non reciprocal Faraday rotation and the 45 degree polarizer transmission axis angle add so that the polarization transmitted by the output polarizer is rejected at the input polarizer Your Newport Faraday Isolator is labeled with a serial number on the base clamp of the device 1 2 Safety The operational hazards presented to operating personnel by the use of your Newport Faraday Isolator are listed below An explanation of how the Faraday Isolator is designed together with procedures users can employ to eliminate or minimize these hazards are also listed 1 Danger of sharp ferromagnetic objects being attracted to the residual permanent magnet fields outside of the isolator This hazard is of most concern if such fields cause flying objects when being handled Your Newport Faraday Isolator requires strong internal magnetic fields to operate properly Efforts have been made to minimize external fields from the device while still maintaining a relatively small and cost effective package The external fields are designed to be well within federal safety guidelines which limit external fields from magnetic devices to be less than 2K Gauss at a radial distance of 5cm from the outside of the device However such fields can be sufficient to attract nearby objects such as knives and razor blades Should attraction of such objects begin to occur there would be a strong attractive force directing these objects towards the2. Faraday Isolator Low Power ISO Series User s Manual GD Newport Experience Solutions ji Preface Warranty Newport Corporation warrants that this product will be free from defects in material and workmanship and will comply with Newport s published specifications at the time of sale for a period of one year from date of shipment If found to be defective during the warranty period the product will either be repaired or replaced at Newport s option To exercise this warranty write or call your local Newport office or representative or contact Newport headquarters in Irvine California You will be given prompt assistance and return instructions Send the product freight prepaid to the indicated service facility Repairs will be made and the instrument returned freight prepaid Repaired products are warranted for the remainder of the original warranty period or 90 days whichever is longer Limitation of Warranty The above warranties do not apply to products which have been repaired or modified without Newport s written approval or products subjected to unusual physical thermal or electrical stress improper installation misuse abuse accident or negligence in use storage transportation or handling This warranty also does not apply to fuses batteries or damage from battery leakage THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FIT
3. Meter should be sensitive enough to detect power levels below 0 01mW or 40dB of the input signal used As a reference 40dB is a factor of 1 10000 and 10dB is a factor of 1 10 If necessary loosen the Baseplate Clamp Screw to allow the Output Polarizer transmission axis to be rotated parallel to the source laser polarization axis Re tighten this screw when complete Loosen the button head Input Polarizer Clamp Ring screws just enough to that the Input Polarizer Mount can be rotated the Input Polarizer is opposite to the laser source at this point Rotate the Input Polarizer Mount until a minimum reading is indicated on the Power Meter Re tighten the Input Polarizer Clamp Ring Screws The minimum reading should be at least 30dB 1 1000 of the input signal If not call Newport for assistance see Page iii The Faraday Isolator is now optimized to operate at the new laser source operating wavelength It may now be installed for operation in transmission with the laser source as per Section 1 3 1 and the procedure outlined in Section 1 3 2 A C Waveplate Option and Adjustment It is possible to order a Faraday Isolator with a half waveplate on the output Should any of the above adjustments become necessary or if the desired output polarization changes the waveplate will need to be adjusted To re align the waveplate loosen the radially oriented set screw in the output polarizer mount and rotate the waveplate until the desired output polariza
4. NESS FOR A PARTICULAR USE NEWPORT CORPORATION SHALL NOT BE LIABLE FOR ANY INDIRECT SPECIAL OR CONSEQUENTIAL DAMAGES RESULTING FROM THE PURCHASE OR USE OF ITS PRODUCTS First printing 2005 2005 by Newport Corporation Irvine CA All rights reserved No part of this manual may be reproduced or copied without the prior written approval of Newport Corporation This manual has been provided for information only and product specifications are subject to change without notice Any change will be reflected in future printings Newport Corporation 1791 Deere Avenue Irvine CA 92606 USA P N 44757 01 Rev C Preface Technical Support Contacts North America amp Asia Europe Newport Corporation Service Dept Newport MICRO CONTROLE S A 1791 Deere Ave Irvine CA 92606 Zone Industrielle Telephone 949 253 1694 45340 Beaune la Rolande France Telephone 800 222 6440 x31694 Telephone 33 02 38 40 51 56 Asia Newport Opto Electronics Technologies 253 Aidu Road Blid 3 Fir 3 Sec C Shanghai 200131 China Telephone 86 21 5046 2300 Telephone 86 21 5046 2323 Newport Corporation Calling Procedure If there are any defects in material or workmanship or a failure to meet specifications promptly notify Newport s Returns Department by calling 1 800 222 6440or by visiting our website at www newport com returns within the warranty period to obtain a Return Material Authorization Number RMA Return the product to Newport Corporat
5. eeeeeeeceeee 6 1 3 2 Tuning your Faraday solator ccccccccccccceeceeeeeseeeeeeeseeeeees 9 IE SPCCUICATIONS gerri a suis aiviatees 11 2 Factory Service Information 12 2 1 Service Form c ccccecsccescececcescececsececcsccccensecceseccecensecesceceecsscecensesens 2 1 General Information 1 1 Introduction Your Newport Faraday Isolator is essentially a uni directional light valve It is used to protect a laser source from destabilizing feedback or actual damage from back reflected light Figure 1 below identifies the main elements of your Faraday Isolator BASE PLATE BASE CLAMP ms WITH SCREW HG INPUT POLARIZER OUTPUT POLARIZER TRANSMISSION ARROW Figure 1 Newport s 650 980nm Low Power Faraday Isolator The Faraday Isolator is a cylindrically shaped magneto optic device Strong Neodymium Iron Boron permanent magnets are used to generate high 210 000 Gauss axially oriented fields within the magnet housing The strong longitudinal field causes 45 degrees of non reciprocal polarization rotation for propagating light via the Faraday Effect in the Terbium Gallium Garnet T GG crystal located within the magnet housing In operation the magnet housing is sandwiched between input and output polarizers that have their transmission axis oriented 45 degrees relative to each other to account for the 45 degrees of Faraday rotation in the TGG crystal in the forward transmission direction In the reverse
6. he direction of any rejected polarizations at the input polarizer is important they can be determined by noting that the dot superimposed on one of the Endplate scribe lines is associated with the direction that a backward propagating beam will be directed Re tighten the Baseplate Clamp Screw B Fine Wavelength Adjustment Each of the 650 780 850 and 980nm isolators may be tuned over the wavelength range specified in section 1 4 Tuning is achieved by adjusting the relative angle between the input and output polarizers For wavelengths longer than the central wavelength the Faraday rotation is less than 45 degrees For wavelengths shorter than the central wavelength the Faraday rotation is more than 45 degrees and therefore the device may be tuned for maximum extinction with a small transmission loss illustrated by the wavelength tuning curves in section 1 4 The 3dB bandwidth of the isolators ranges from 12nm at 650nm to 20nm at 980nm in increasing value For maximum extinction manually tune the device to the appropriate wavelength With the source laser operating at an average power of 100mW or less attenuate the beam if necessary to achieve such a low power level direct the source laser beam through the Faraday Isolator in the reverse direction through the Output Polarizer first and then through the Input Polarizer Use an IR viewer to view the transmitted radiation to ensure that it 1s directed onto a Power Meter The Power
7. interior of the magnet housing This could be particularly likely to result in injury e g a cut or puncture wound if such attraction occurred while the device was being handled particularly if a body part of the operating personnel is near a beam Aperture i e end of the device To minimize the above risks remove all loose ferromagnetic objects from the path over which your Newport Faraday Isolator is to be moved prior to attempting to move it Do not pick up the isolator by its ends i e apertures where the attractive magnetic fields are strongest Always pick the isolator up along its sides Reflection of rejected beams from the input and output polarizer The polarizer covers have been positioned at the factory to block all beams rejected from the polarizers In the event that your Faraday Isolator will be used with transmitted average powers in excess of 25W or will block backward propagating light in excess of 0 5W average power these polarizer covers must be rotated to allow rejected beams to exit see Figure 1 onto user supplied beam dumps These rejected beams can represent a hazard to users and or their colleagues Care must be exercised to ensure that all rejected beams both transmission and isolation directions are accounted for and terminated into functional beam dumps Wherever possible keep the strongest rejected beams in the horizontal plane of the table or otherwise safest direction typically down into the table Alway
8. ion freight prepaid clearly marked with the RMA and we will either repair or replace it at our discretion Newport is not responsible for damage occurring in transit and is not obligated to accept products returned without an RMA E mail rma service newport com When calling Newport Corporation please provide the customer care representative with the following information e Your Contact Information e Serial number or original order number e Description of problem i e hardware or software To help our Technical Support Representatives diagnose your problem please note the following conditions e Is the system used for manufacturing or research and development e What was the state of the system right before the problem e Have you seen this problem before If so how often e Can the system continue to operate with this problem Or is the system nonoperational e Can you identify anything that was different before this problem occurred iV Preface Table of Contents hb uci ii Technical Suppor CONTACTS 220 sisi rra dao a a iii Table Of COMEN Seenen ni Hai Ioa IEEE LEEREN UE EEEE EEEE EEESC 1V 1 General Information 1 T InttOONWCBOfE c ian t duod edu edu do d to Ro dudum a 1 EA ie e MNENENENERRENRERERRERERERERREREREREREENENRENERERRETNEENEM 2 ES B oL TOIT T uuuu 4 1 3 1 Using your Faraday Isolator eeeee
9. mizing the required footprint of the device Steel ferromagnetic ball drivers or other such wrenches will be attracted to the external magnetic field surrounding the device If possible use anti magnetic stainless steel or titanium tools If ferromagnetic tools are used it is desirable to introduce them slowly toward the device from the sides along the direction of the baseplate flange slots One important consideration is that this isolator is intended to be used at low power The device is very compact given the physical size of the polarizers used in its construction One drawback of this is that the rejected power is absorbed in the polarizers themselves and therefore damage thresholds are limited to 25W cm CW Um LL T3 T3 T3815 3s 38 T3 T8 lom lom loeum oen Figure 8 Dimensions of Low Power Faraday Isolator in Inches 1 3 2 Tuning your Faraday Isolator A Adjusting Input Polarization The transmission axis of the Input Polarizer is parallel to the scribe line found on the Input Polarizer Endplate If the linear polarization of the laser source is geometrically known aligning the Input Polarization of the Faraday Isolator to that of the laser source is straightforward Simply loosen the 42 56 socket head Baseplate Clamp Screw in the Baseplate until the magnet housing rotates freely Continue to rotate the magnet Housing until the Input Polarizer transmission axis scribe line is aligned to that of your laser source If t
10. n of the device following tuning as per instructions in section 1 3 2 B Low Power Isolator Transmission by Model 100 95 90 4 E 80 75 4 70 CN 65 600 700 800 900 1000 Wavelength nm 650 780 850 980 8 Transmission 2 Factory Service Information 2 1 Service Form GO Newport Name Company Address Country P O Number Item s Being Returned Model Description Newport Corporation U S A Office 800 222 6440 FAX 949 253 1479 Return Material Authorization Please obtain RMA prior to return of item Phone Number FAX Number Serial Reason for return of goods please list any specific problems Notes Newport Corporation Worldwide Headquarters 1791 Deere Avenue Irvine CA 92606 In U S 800 222 6440 Tel 949 863 3144 Fax 949 253 1680 Internet sales newport com Newvvport Experience Solutions Visit Newport Online at www newport com BSI GO Newport Corporation Irvine California has been certified compliant with ISO 9001 by the British Standards Institution ISO 9001 FM 27207 Printed in the U S
11. ned for a horizontal input polarization The screw hole located on the side of the polarizer mount indicates the approximate angular position of the polarizer transmission axis and maximum transmission is observed when the input polarization is aligned to this angle the default orientation is horizontal Figure 4 shows a device aligned for a vertical input polarization with the transmission axis rotated 90 degrees with respect to that depicted in Figure 3 Y axis 090 Positive Z rotation 2 ul Z axis Direction of Beam Propagation Direction of arrow on device X axis 000 md bu Source 1 3 1 Using your Faraday Isolator Observe the guidelines for safe use of your Faraday Isolator found in Section 1 2 above when removing your isolator from its shipping container Do not remove the protective dust cover end caps from the polarizers until the device is in a clean relatively dust free environment Save the protective end caps packaging material and containers in the event that the device should ever need to be returned to Newport Verify that the Input and Output polarization states are consistent with the intended mode of operation If not either send the device back to Newport see Page 111 or if desired re adjust the isolator as required see Section 1 3 2 With the source laser off or running at very low power less than 100mW position the Faraday Isolator such that the source laser beam can be directed through the Inp
12. s wear laser safety glasses goggles consistent with all laser frequencies and power levels present See the following sections for further details Failure of operating personnel to observe standard laser safety by sighting down through the isolator when laser radiation is present The optical elements within the Newport Faraday Isolators can be transmissive throughout the visible and near infrared Consequently it is never appropriate to view through the device in either the transmission or isolation direction when laser radiation is present even with laser safety goggles Never sight through your Newport Faraday Isolator in either direction when there is any possibility of laser radiation being present Harm caused by external magnetic fields Your Newport Faraday Isolator has been designed to meet existing federal safety guidelines for external fields as noted previously Such guidelines could change in the future as more information becomes known or reviewed regarding the interaction between magnetic fields and human health Since there exist various claims regarding the potential harmful and beneficial effects of magnetic fields on humans it is prudent to limit interaction with these fields as much as possible Personnel with any magnetically sensitive implants such as pacemakers should consult their medical doctor regarding any potential complications which could arise from the isolator external magnetic fields Other non heal
13. th related hazards The Faraday Isolator external magnetic fields can draw ferromagnetic objects into the magnet housing that can damage the optical elements within the device Keep a suitable area in all directions around the Faraday Isolator clear of any loose ferromagnetic objects Ideally use non magnetic tools such as stainless steel or titanium and hardware to secure the Faraday Isolator If only ferromagnetic tools are available use extreme care when using them around the Faraday Isolator It is always helpful to bring such tools towards an aperture or end radially rather than along the optical beam path Doing this ensures that the fields will tend to pull such objects into the magnet housing endplate rather than into the optical aperture Where possible use two hands one to hold the tool and the other to guide it to the desired destination Another concern regarding external magnetic fields is their effect on magnetically sensitive devices The external fields are strong enough to induce a pulse of current in electronic devices such as digital watches that can destroy them The fields can also disrupt the operation of other mechanical devices with ferromagnetic parts in them Finally the external fields can erase information from magnetic strips such as are found on credit and ID cards Remove all magnetically sensitive materials and devices such as watches computer hard drives and magnetic strips from operators prior to working in
14. the proximity of an isolator 1 3 Operation NOTE OUTPUT NOTE INPUT POLARIZATION IS 45 DEGREES BASE CLAMP a WITH INPUT POLARIZATION ADJUSTMENT AXIS LINES SCREW H 45 V POLARIZATION TRANSMISSION AXIS SCRIBE LINE WAVEPLATE HOLDER INPUT APERTURE Figure 2 View of Faraday Isolator and Tuning Features The low power Faraday Isolator uses dichroic sheet polarizers at both the input and output of the device These broadband polarizers absorb the rejected transmission and are therefore only effective for low power applications The inscribed arrow on the base clamp displays the transmission direction The output polarizer is seen to be oriented with its transmission axis rotated 45 degrees relative to the input polarization The input polarization shown is vertical The central magnet housing together with the TGG crystal residing in its center forms a Faraday Rotator The Faraday Rotator rotates the input transmission axis by 45 degrees so that transmitted light has a polarization aligned with the output transmission axis The input and output polarizers work in conjunction with the central Faraday Rotator to form a Faraday Isolator Though the overall size of the device varies depending on the model the operation of the polarizer mounts are identical Figure 3 Horizontal Input Polarization Figure 4 Vertical Input Polarization POLARIZATION IS AT Figure 3 shows a device alig
15. tion is achieved Retighten the waveplate set screw Do not over tighten A waveplate may also be used in the input of the device if necessary 1 4 Specifications CW Damage Center Wavelength Tunable Range Isolation Transmission Threshold nm nm dB Wiem Two State Option Faraday Isolators may be used in series to obtain 60 dB isolation mounted on a common baseplate Mounting Options Cylindrical housings are inserted into a clamping device that provides 8 32 screw holes and may be mounted onto a standard post All devices include a base for mating with 14 20 screw holes Notes 1 Transmission This is measured form the center wavelength Tunable transmissions will be wavelength dependent Please consult the spectra below 2 Damage Threshold Damage threshold is limited by cemented optics and broadband AR coatings for wavelength tunability For higher damage threshold applications please contact Newport 3 Operating Temperature Performance of Newport s Faraday Rotators Isolators is related to operating temperature For information on the effect of operating temperature on Newport s Faraday Rotators Isolators please review our technical bulleting Effects of Temperature on Newport s Faraday Rotators Isolators 4 Center Wavelength This refers to the wavelength specified for 45 2 degrees and is not necessarily the median of the wavelength range 5 Tunable Transmission The below graphs show the transmissio
16. ut Aperture Critical alignment of the Faraday Isolator should be done at low power less than 100mW in order to prevent optical damage to your isolator or laser source Use IR cards or viewers to ensure that the source laser beam is centered on the input and output apertures The clear aperture of this device is 4mm centered on the circular cross section of the magnet body There are different mounting options for establishing appropriate beam height It is also preferable to use an IR viewer to ensure that weak reflections from AR coated optical surfaces in the Faraday Isolator are not being directed back into the source laser The optical surfaces in the Faraday Isolator are angled slightly to reduce these reflections Increasing the distance between the Faraday Isolator and the source laser can also help ensure that no reflections couple back into the source laser if necessary Alternatively if the beam used is smaller than the aperture of the device by a reasonable margin the device may be slightly tilted At this point the Faraday Isolator should be secured to the work surface with two 2 1 4 20 or M6 screws one for each slot in the baseplate flanges Alternatively the baseplate may be removed from the baseclamp by removing two 8 32 screws on the bottom side of the base plate Then the baseclamp isolator assembly may be mounted to a standard laboratory post with an 8 32 set screw or may be conveniently mounted into laser systems mini
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