THORLABS EDU-MINT2 User Manual

Michelson interferometer kit

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EDU-MINT2

EDU-MINT2/M

Michelson Interferometer Kit

User Guide

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Page 1 EDU-MINT2 EDU-MINT2/M Michelson Interferometer Kit User Guide...
Page 2: Table Of Contents
Michelson Interferometer Table of Contents Chapter 1 Warning Symbol Definitions ..........1 Chapter 2 Safety .................2 Chapter 3 Description ................3 Chapter 4 Kit Components ..............4 4.1 Basic Components of the Interferometer ...... 4 4.2 Components to Observe the 2 Interferometer Output .. 6 4.3 Components for the Refractive Index Measurement .. 6 4.4 ...
Page 3 Chapter 11 Modern Michelson Interferometry – LIGO ....51 Chapter 12 Troubleshooting ............. 52 Chapter 13 Appendix ................. 54 Chapter 14 Regulatory ............... 56 Chapter 15 Thorlabs Worldwide Contacts ........57 ...
Page 4: Chapter 1 Warning Symbol Definitions
Michelson Interferometer Chapter 1: Warning Symbol Definitions Chapter 1 Warning Symbol Definitions Below is a list of warning symbols you may encounter in this manual or on your device. Symbol Description Direct Current Alternating Current Both Direct and Alternating Current Earth Ground Terminal Protective Conductor Terminal Frame or Chassis Terminal...
Page 5: Chapter 2 Safety
Michelson Interferometer Chapter 2: Safety Chapter 2 Safety WARNING The laser module is a class 2 laser, which does not require any protective eyewear. However, to avoid injury, do not look directly into the laser beam. DO NOT STARE INTO BEAM CLASS 2 LASER PRODUCT MTN006503-D02 Page 2...
Page 6: Chapter 3 Description
Michelson Interferometer Chapter 3: Description Chapter 3 Description The objective of this experiment package is to become familiar with the interferometer as a highly sensitive measuring instrument. Since the applications in technology and industry are extremely diverse, this package includes various experiments that highlight different aspects of physics.
Page 7: Chapter 4 Kit Components
Michelson Interferometer Chapter 4: Kit Components Chapter 4 Kit Components In cases where the metric and imperial kits contain parts with different item numbers, metric part numbers and measurements are indicated by parentheses unless otherwise noted. Basic Components of the Interferometer 1 x CPS532-C2 1 x RDF1 Collimated Laser Diode...
Page 8 Michelson Interferometer Chapter 4: Kit Components 2 x BA2(/M) Base, 1 x LMR1(/M) 1 x EDU-VS1(/M) 2" x 3" x 3/8" Ø1" Lens Mount Plastic Viewing Screen (50 mm x 75 mm x 10 mm) 1 x LB1471 N-BK7 Bi-Convex Lens, 1 x CCM1-BS013(/M) 4 x UPH1.5 (UPH30/M) Ø1", f = 50.0 mm, Uncoated...
Page 9: Components To Observe The
Michelson Interferometer Chapter 4: Kit Components Components to Observe the 2 Interferometer Output 1 x EBS1 Ø1" Economy 1 x TR1.5 (TR40/M) 1 x LMR1(/M) Beamsplitter Ø1/2" (Ø12.7 mm) Post, Ø1" Lens Mount 1.5" (40 mm) Long Components for the Refractive Index Measurement 1 x FP01 1 x PR01(/M) General Purpose...
Page 10: Components For Interference With Leds
Michelson Interferometer Chapter 4: Kit Components Components for Interference with LEDs 2 x LEDMT1F 1 x LEDW7E 2 x LED631E USB-Powered LED Mount, White Light LED, 15 mW, 635 nm LED, 4 mW, 62 Ω Resistor, USB to 7.5° Half Viewing Angle, 20°...
Page 11: Components For The Thermal Expansion Setup
Michelson Interferometer Chapter 4: Kit Components Components for the Thermal Expansion Setup 1 x Aluminum Post 1 x ME1-G01 1 x MH25 Ø12.7 mm, 90 mm Long, Ø1" Aluminum Mirror Mirror Holder for Ø1", Tap Accepts MH25 2.5 to 6.1 mm Thick Optics 1 x RA90(/M) Right-Angle Post Clamp, 1 x TR2 (TR50/M)
Page 12: Imperial Kit Hardware
Michelson Interferometer Chapter 4: Kit Components Imperial Kit Hardware Type Quantity Type Quantity 1/4"-20 x 1/4" Cap Screw 6-32 x 1/4" Cap Screw 1/4"-20 x 3/8" Cap Screw 8-32 x 3/8" Cap Screw 1/4"-20 x 1/2" Cap Screw 8-32 x 5/8" Cap Screw 1/4"-20 x 5/8"...
Page 13: Chapter 5 Setup And Adjustment
Michelson Interferometer Chapter 5: Setup and Adjustment Chapter 5 Setup and Adjustment This chapter discusses how to assemble the various components and explains how to set up and adjust the interferometer. Assembling the Components First screw the four rubber feet to the four holes in the bottom of the breadboard using the 1/4"-20 x 1/2"...
Page 14 Michelson Interferometer Chapter 5: Setup and Adjustment The mirror is locked in place using the nylon-tipped setscrew. Now you need to assemble the laser, beamsplitter and movable mirror as additional components of the setup. Laser Beamsplitter Movable Mirror Components: Components: Components: CPS532-C2 Laser CCM1-BS013(/M)
Page 15 Michelson Interferometer Chapter 5: Setup and Adjustment The elements installed so far are the basic components of the interferometer. The next set of components will be used with the interferometer in the various experiments explained in this manual. Ø1" Beamsplitter: To assemble the second beamsplitter, remove the retaining ring from the LMR1(/M) mount, place the beamsplitter in the mount and attach the retaining ring.
Page 16 Michelson Interferometer Chapter 5: Setup and Adjustment SM05L03 lens tube in from the other side. The addition of the lens tube helps to block light emitted by the LED at large angles from reaching the screen. To operate the LED, connect the LEDMT1F to the DS5 power supply via the USB to micro-B USB cable and use the USB extension cable if needed.
Page 17 Michelson Interferometer Chapter 5: Setup and Adjustment Figure 1 Placing the Laser and the First Mirror Install the beamsplitter and the screen. Ensure that the beam is split at a 90° angle. This can be achieved by observing the secondary reflections on the screen. When they coincide with the primary reflection, the beamsplitter is at a 90°...
Page 18 Michelson Interferometer Chapter 5: Setup and Adjustment It is possible that a slight deviation occurs in the vertical direction (as shown in Figure 3). This does not affect the measurements in the experiments. The deviation means that there is a slight tilt among the laser, beam splitter and translation stage. To get rid of it, either the translation stage or the beam splitter would have to be mounted kinematically which in turn would compromise the stability.
Page 19 Michelson Interferometer Chapter 5: Setup and Adjustment You should now see the two partial beams as bright spots on the screen. Tip and tilt the second mirror until they overlap. Finally, place the lens between the laser and the beamsplitter. You may already see interference rings.
Page 20 Michelson Interferometer Chapter 5: Setup and Adjustment Placing the lens behind the beamsplitter and moving the screen away from the breadboard (as shown in Figure 6) results in a pattern of stripes instead of rings (as shown in Figure 7). Whether you choose to count rings or stripes is a matter of personal preference.
Page 21: Chapter 6 Theoretical Background
Michelson Interferometer Chapter 6: Theoretical Background Chapter 6 Theoretical Background This chapter discusses the essential theoretical foundations that apply to the experiments which follow. The chapter begins with a brief discussion of interference in general and an explanation of the form of the interference pattern. Coherence is discussed next since one experiment involves interference with LEDs.
Page 22 Michelson Interferometer Chapter 6: Theoretical Background Here is the phase, the value of which is established by the actual optical path. The factor √ ⋅ is therefore explained because the beam in path 1 is first transmitted and then reflected. The description of the beam in path 2 is similar, but the beam is first reflected and then transmitted.
Page 23 Michelson Interferometer Chapter 6: Theoretical Background                    Figure 9 Normalized intensity distribution on the screen depending on the path length difference. To understand this, one has to look Cement at the phase shifts on a beamsplitter.
Page 24 Michelson Interferometer Chapter 6: Theoretical Background Size and Shape of the Pattern We have now clarified what the interference pattern of a plane wave and/or at the central point looks like. Naturally the real interference pattern appears different than that of a plane wave, since the laser diverges on its way to the screen.
Page 25: Determining The Wavelength
Michelson Interferometer Chapter 6: Theoretical Background adjust the interferometer. In order to find a configuration with nearly identical arm lengths, the central maximum needs to be as large as possible. A nice way to visualize the ring pattern is to overlap two wavefronts.
Page 26: Coherence
Michelson Interferometer Chapter 6: Theoretical Background Coherence The topic of coherence is highly complex. Terms such as the contrast of an interference pattern, correlation functions and the Wiener-Chintschin theorem are essential for a deeper understanding. Therefore only a brief abstract can be provided here, limited to the descriptive values of coherence time and coherence length Coherence in the largest sense describes the capacity of light to create interference.
Page 27 Michelson Interferometer Chapter 6: Theoretical Background Linked to the coherence time, the coherence length is Δ . This is the path the light can travel within the coherence time, that is: Δ ⋅ Δ (11) Here the propagation in air was assumed with the refractive index 1. While coherence is a complex topic, the coherence length in case of an interferometer is more straightforward –...
Page 28 Michelson Interferometer Chapter 6: Theoretical Background Figure 14 Interferometer with (a) plate beamsplitter and (b) compensator plate (refraction on the surface was disregarded in this sketch) First let us examine Figure 14(a). Here the laser is reflected off of the beamsplitter when it is inside of the glass substrate, then reflected by the mirror, and finally transmitted through the beamsplitter, therefore propagating through the glass substrate thrice on its way to the screen.
Page 29 Michelson Interferometer Chapter 6: Theoretical Background Selecting the Mirrors The surface flatness of the mirrors used in this kit are specified as better than /10, compared to economy mirrors which have a surface flatness of 5 . It is not absolutely necessary to use this quality of mirror but it provides some advantages.
Page 30: Interferometric Determination Of The Refractive Index
Michelson Interferometer Chapter 6: Theoretical Background Interferometric Determination of the Refractive Index Determining the refractive index of a solid (transparent if possible) is one application where a Michelson interferometer can be used as a sensitive measuring instrument. Here the solid is first placed in one arm of the interferometer. Then it is slowly rotated so that the optical path in this interferometer arm changes.
Page 31: Determining A Thermal Expansion Coefficient
Michelson Interferometer Chapter 6: Theoretical Background ΔOptical Path 2 ⋅ Δ 1 ⋅ Δ 2 ⋅ (18) The factor of 2 appears in the equation because the light passes along the path twice. The path length difference is derived from the light-dark transitions via ⋅...
Page 32: Using The Interferometer As A Spectrometer
Michelson Interferometer Chapter 6: Theoretical Background (24) Δ ⇒ α Δ where the factor ½ is once again due to the path of the laser to and from the mirror that was shifted. Using the Interferometer as a Spectrometer A very elegant application of an interferometer is to use it as a spectrometer. Assume the light source emits two different wavelengths.
Page 33 Michelson Interferometer Chapter 6: Theoretical Background which means the contrast becomes zero . Dividing by and expressing Δ transforms this statement to ⋅ Δ (29) 2 Δ 2 Δ The term Δ which results in the statement is negligibly small in comparison to (30) Δs 4 Δλ...
Page 34: Chapter 7 Experiments And Examples
Michelson Interferometer Chapter 7: Experiments and Examples Chapter 7 Experiments and Examples This chapter discusses the various experiments that can be performed with this experiment package. Numerical examples that can be expected under realistic conditions are provided as well. Preliminary Tests Assemble the Michelson interferometer if you have not already done so.
Page 35 Michelson Interferometer Chapter 7: Experiments and Examples Note: Observing the pattern on the beamsplitter requires a dark room with very little stray light. Finally, place the second beamsplitter (use one of the post holders from the LED assembly) between the cube beamsplitter and the lens. The newly introduced beamsplitter will also reflect a fraction of the laser light towards the experimenter.
Page 36: Determining The Laser Wavelength
Michelson Interferometer Chapter 7: Experiments and Examples Determining the Laser Wavelength One typical application of an interferometer is to determine the wavelength of the incident light. This measurement is performed through controlled shifting of one mirror, which causes a change in the interference pattern. Depending on the direction the mirror is moved relative to the second mirror, the concentric circles either expand out from the center (with new ones constantly appearing in the center) or they shrink into the center (where they disappear).
Page 37: Using The Interferometer As A Spectrometer
This is consistent with the specifications of the CPS532-C2 laser diode. Figure 19 shows an example of a typical spectrum (taken from www.thorlabs.com). For a more precise measurement, we recommend using piezo crystals, see Chapter 10: Ideas for Additional Experiments.
Page 38: Interference With Leds, Coherence
Michelson Interferometer Chapter 7: Experiments and Examples CPS532-C2 Typical Spectrum    531.0 531.5 532.0 532.5 533.0 Wavelength (nm) Figure 19 Typical spectrum of a CPS532-C2 laser diode. The spectral composition of the light varies strongly with changing temperature of the housing. The temperature of the housing will be different from the room temperature.
Page 39 Michelson Interferometer Chapter 7: Experiments and Examples end of the mirror’s translation range without finding a pattern, shift it to the other end. If you have not found a pattern along the entire translation range of the mirror, the preliminary adjustment with the laser was not accurate enough.
Page 40 Michelson Interferometer Chapter 7: Experiments and Examples Then shift the mirror in the other direction, also until the contrast of the interference pattern has decreased significantly. The coherence length is approximately equal to the distance between the two mirror positions where interference is still visible. Sample result: The result of a test measurement was approximately 25 µm.
Page 41: Refractive Index Determination
Michelson Interferometer Chapter 7: Experiments and Examples Experiment 9: Once you have found the correct position from experiment 8 for red interference, you can replace the red LED with the white one in order to find the mirror position to observe white light interference (it’s within the range for the red light interference).
Page 42 Michelson Interferometer Chapter 7: Experiments and Examples Figure 21 The setup for measuring the refractive index of Plexiglas (left) and the micrometer drive (fine adjustment screw) and locking setscrew on the rotation platform (right). When the setscrew is locked, the fine adjustment is engaged. The stage is then rotated by turning the micrometer drive.
Page 43: Thermal Expansion Coefficient
Michelson Interferometer Chapter 7: Experiments and Examples Aligned Lines: 182° 20’ Sample result: The following values were determined by students in practical tests. The reference value for the refractive index of the Plexiglas plate that was used is 1.49. Number of Rotation Plate Thickness According to...
Page 44 Please note that the supplied flexible foil heater with thermistor and banana plugs was chosen as a cost effective combination under the assumption that a standard controllable power supply is available. Thorlabs offers more sophisticated heater controllers, allowing for direct temperature feedback by making use of the thermistor sensor on the foil heater, e.g.
Page 45 Michelson Interferometer Chapter 7: Experiments and Examples Sample result: The following values were determined by students in practical tests. # of Fringes in Temperature Temperature Calculated Voltage Start Total # of Length (°C) (°C) (°C) -Interval Fringes (cm) 9.0004 9.0013 9.0031 11.2 9.0054...
Page 46: Chapter 8 Experiment Overview
Michelson Interferometer Chapter 8: Experiment Overview Chapter 8 Experiment Overview Preliminary Tests and Determining the Laser Wavelength Set the Michelson interferometer up and adjust it. Change the length of an interferometer arm by moving the mirror (the one in the kinematic holder).
Page 47 Michelson Interferometer Chapter 8: Experiment Overview Thermal Expansion Coefficient 15. Remove the rotation platform from the setup and replace the moveable mirror with the setup to measure thermal expansion. Adjust the interference pattern again so that you can count the transitions easily. 16.
Page 48: Chapter 9 Questions
Michelson Interferometer Chapter 9: Questions Chapter 9 Questions This list of questions also provides a starting point for topics that can be examined in relation to the Michelson interferometer (even beyond this experiment package).  What is the difference in the interference patterns when the arms are (a) of the same length and (b) of different lengths? ...
Page 49: Chapter 10 Ideas For Additional Experiments
This effect can be shown with the help of the Michelson interferometer by substituting the CPS532-C2 laser with a laser for which the pumping current can be manually adjusted. An example is the Thorlabs L658P040 Laser Diode in combination with the TLD001 Driver, SR9A-DB9 Mount, and LTN330-A Adjustable Collimation Tube.
Page 50 [e.g. Thorlabs CCS100(/M)]. This experiment can also give a deeper understanding of very common laser diodes and their working principle.
Page 51: Coherence Length
Adjustment of White Light Interference via a Spectrometer In order to facilitate the adjustment of the Michelson Interferometer especially for white light interference, a spectrometer (e.g. Thorlabs CCS100) can be used instead of the naked eye. Then, one replaces the screen by the light collection element of the spectrometer and views the spectrum with a suitable software.
Page 52 Figure 26 shows three example spectra, obtained with a Thorlabs CCS100 spectrometer and the Thorlabs OSA software for a LEDW7E white light LED. The black curve was recorded at large path length differences and thus shows the spectrum of the LEDW7E without any interference effects.
Page 53 The advantage of a photodetector is that the voltage values can be recorded using a digital oscilloscope and evaluated without additional software. A possible setup using Thorlabs components is as follows: 1x SM05PD1A Silicon Photo Diode, 1x SM05D5 Iris, 1x SM05M10 Lens Tube,...
Page 54: Chapter 11 Modern Michelson Interferometry - Ligo
Michelson Interferometer Chapter 11: Modern Michelson Interferometry – LIGO Chapter 11 Modern Michelson Interferometry – LIGO A recent application of the Michelson interferometer that attracted a lot of international attention is gravitational-wave detection. Gravitational waves are oscillations in space-time curvature produced by colliding black holes, neutron stars, and other astrophysical processes that involve a dense concentration of mass-energy moving at relativistic speeds.
Page 55: Chapter 12 Troubleshooting
Michelson Interferometer Chapter 12: Troubleshooting Chapter 12 Troubleshooting  The laser spots superpose, but there is no interference. Check whether all of the components have been positioned as precisely as possible (Is there a 90° beam angle after reflection? Is the height of the beam above the plate at the screen the same as it is directly at the laser?).
Page 56 Michelson Interferometer Chapter 12: Troubleshooting proceed with fine-tuning using the red LED and the moveable mirror. When the LED is in the setup, the mirror has to be shifted until interference can be observed. If no interference can be observed along the entire translation path of the mirror, the ...
Page 57: Chapter 13 Appendix
Michelson Interferometer Chapter 13: Appendix Chapter 13 Appendix Determining the refractive index was discussed in Section 6.4. Here the calculation that leads to equation (20) is presented in detail. The content discussed in Chapter 6 on the physical and optical path is presumed to be known here. Screen Screen Screen...
Page 58 Michelson Interferometer Chapter 13: Appendix We now have almost everything we need for equation (20). First we want to point out Snell’s law of refraction, according to which 1 ⋅ sin ⋅ sin (39) applies, where we assumed the refractive index of air with a good approximation of 1. For a subsequent calculation step, one still needs (40) cos arcsin...
Page 59: Chapter 14 Regulatory
Waste Treatment is Your Own Responsibility If you do not return an “end of life” unit to Thorlabs, you must hand it to a company specialized in waste recovery. Do not dispose of the unit in a litter bin or at a public waste disposal site.
Page 60: Chapter 15 Thorlabs Worldwide Contacts
Michelson Interferometer Chapter 15: Thorlabs Worldwide Contacts Chapter 15 Thorlabs Worldwide Contacts For technical support or sales inquiries, please visit us at www.thorlabs.com/contact for our most up-to-date contact information. USA, Canada, and South America UK and Ireland Thorlabs, Inc. Thorlabs Ltd.
Page 62 www.thorlabs.com...

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