Changes

[[Image:neoscanfig_1_1.png|thumb|right|400px|<i><b>Figure 1.1</b>: EO modulation of an optical signal.</i>]] The [[NeoScan]] real-time field measurement & scanning system provides an entirely new capability for the measurement of high-intensity electric fields. This technology is based on the Pockel’s effect which measures the phase-retardance of an optical beam due to an impinging electric field. This electro-optic effect is observed in non-centrosymmetric crystals when an electric field is directed along certain crystal axes causes a change in the indices of refraction encountered by an incident optical beam. Figure 1.1 shows the basic principle of the electro-optic effect. The electro-optic effect provides a means of modulating the phase or intensity of the optical radiation. In another sense, this effect also makes it possible to detect the presence of an electric field impinging on the crystal. The polarization of an optical beam travelling through a crystal is altered by the electric field in that crystal. The comparison of polarization states allows determination of the amplitude and phase of the existing RF electric field. Since the electro-optic sensing phenomenon relies on small displacements of the atomic crystal structure, the response time of the process is extremely short. This short response time makes it possible to measure high-frequency electric fields up to the terahertz regime.  <center>[[Image:neoscanfig_1_1.png|thumb|center|400px|<i><b>Figure 1.1</b>: EO modulation of an optical signal.</i>]]</center>

[[Image:neoscanfig_1_2.png|thumb|centerleft|380px|<i><b>Figure 1.2</b>: A single-axis EO probe. The probe tip is protected by Epoxy to

Figure 1A low noise 1550 nm laser diode is used as optical beam source.3 shows the electric and magnetic fields distribution The optical connections are fiber-based. The beam is delivered to an optical probe. The polarization of a traveling RF wave with a normal the beam is modulated through an electro-optic crystal on the probe shown in typical orientationtip. To detect The modulated beam is reflected back into the maximum electric field in this configurationfiber, and back to the propagation direction mainframe for analysis. An optical analyzer converts the polarization change of the optical beam into an amplitude change. The amplitude is linearly proportional to the strength of the probe should be parallel to external electric field at the Eprobe-field directioncrystal location. In general, a normal EO probe The equation E=αV is only sensitive used to calculate the electric field component parallel to the probe handle, whereas a tangential probe where α is sensitive to the calibration factor, or the slope between the electric field component perpendicular to E (in V/m) and the probe handlemeasured EO signal V (in V/m/uV). YetFor instance, the E-field sensitivity for a calibration factor of 1.082 V/m/uV. a tangential probe depends on its crystal orientation sitting on its tipmeasured EO signal of 1000 uV (0.001 V), corresponds to and electric field of 1.082 V/m/uV x 1000 V = 1082 V/m.

<center>[[Image:neoscanfig_1_4.png|thumb|rightcenter|480px|<i><b>Figure 1.4</b>: An example of a real time measurement of a 6.6 nsec pulse with 10 kV/m peak field strength. The upper trace shown on the oscilloscope is the input signal, and the lower trace is the measured signal.</i>]] A low noise 1550 nm laser diode is used as optical beam source. The optical connections are fiber-based. The beam is delivered to an optical probe. The polarization of the beam is modulated through an electro-optic crystal on the probe tip. The modulated beam is reflected back into the fiber, and back to the mainframe for analysis. An optical analyzer converts the polarization change of the beam into an amplitude change. The amplitude is linearly proportional to the strength of the external electric field at the probe-crystal location. The equation E=αV is used to calculate the electric field, where α is the calibration factor, or the slope between the electric field E (in V</m) and the measured EO signal V (in V/m/uV). For instance, for a calibration factor of 1.082 V/m/uV. a measured EO signal of 1000 uV (0.001 V), corresponds to and electric field of 1.082 V/m/uV x 1000 V = 1082 V/m.center>

<p>The system operates from a 100V or 120V nominal AC power source having a line frequency of 50 or 60 Hz. Before connecting the power cord to a power source, verify that the AC input voltage value is correct. </p>

<p>[[NeoScan]] real-time field measurement and scanning system contains a 40 mW laser diode emitting Class 3B laser radiation at ~1550 nm. The direct output power from the fiber port of each probe channel on the front panel is less than 10 mW. The beam at 1550 nm is invisible to human being and the invisible beam can be hazardous if directed at the eye. Direct exposure of eye to the invisible laser beam must be avoided. </p>

<p>The fans in [[NeoScan]] optical mainframe are required to maintain proper operation. Do not block the vents in the frame box.</p>

<p>In order to avoid EMC/EMI effect, keep the [[NeoScan]] box as far away from the DUT as possible.</p>

<p>Follow standard electrostatic-discharge precaution, including grounding yourself prior to making cable connections to the system. A ground strap provides the most effective grounding and minimizes the likelihood of electrostatic damage.</p>

<p>Handle the probes and the PM fibers with extreme care. </p>

<p>Gently clean and attach the appropriate fiber connectors to the correct fiber port of the [[NeoScan]] system. </p>

<p>Do not excessively pull or bend the fiber.</p>

<p>The probe tip is extremely fragile. Do not strike the probe tip. Always keep the probes in a safe place. </p>

<p>Keep the cables and the fibers handy in safe positions, but out of the way and untangled.</p>

<p>Always use an SMA torque wrench when connecting the SMA connectors.</p>

<p>Do not over-torque the microwave SMA connectors.</p>

<p>Do not over-tighten the optical connectors.</p>

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<p>Place the Y Linear Translation Stage on a stable flat table, preferably an optical table.</p>

<p>Mount the X Linear Translation Stage on the Y Linear Translation Stage using four screws as shown by red screws in Figure 2.2.</p>

<p>Mount the Plate on the X Linear Translation Stage. Fasten its four edges with screws as indicated by green arrows in Figure 2.2.</p>

<p>Place the X, Y, and Z Miniature Translation Stages on the front edge of the Optical Plate and fasten its four edges with screws as indicated by arrows in Figure 2.2.</p>

<p>Attach the Plastic Probe Fixture to the XYZ Miniature Translation Stage.</p>

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</td><td></td><td>[[Image:neoscanfig_2_4.png|thumb|center|350px500px|<i><b>Figure 2.4</b>: How to remove a probe from foam and holding an EO probe and the PM fiber.</i>]]

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<p>Carefully press the both sides of the foam near the probe head, carefully un-wedge the probe from its slot, and then lift the probe. Figure 2.4 shows a picture how to remove a probe.</p>

<p>Carefully remove the probe from the foam, making sure to grasp the probe glass tube and not the probe tip, as this may damage the EO probe.</p>

<p>While holding the probe from its glass tube and keep the fiber sheath in your hand, avoid stretching the white plastic shield part of the fiber. Do not pull the plastic shield part hard.</p>

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[[Image:neoscanfig_2_5.png|thumb|right|500px|<i><b>Figure 2.5</b>: Cleaning a connector end face using a dry cleaning cloth reel-based cassette cleaner.</i>]] The Probes and the fibers are made of a very pure, sensitive, and expensive materials. Treat them with care. Unwind a fiber gently and work out any tangles carefully.

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<p>Plug in the [[NeoScan]] optical mainframe power cord into an electrical receptacle and turn it on. </p>

<p>Connect control computer AC power adapter and turn on the control computer.</p>

<p>Connect USB multi-port Hub AC power adapter to the power. </p>

<p>Connect the [[NeoScan]] Optical Mainframe USB Interface Port on the rear panel to a port on the USB Hub, then connect the control computer USB Interface Port to another port on the USB Hub. The USB Hub is a plug and play device.</p>

<p>Attach the appropriate fiber connectors to the correct fiber ports of the [[NeoScan]] system (Probe 1, Probe 2, or Probe 3), see section 2.6.</p>

<p>[[Image:icon_OBM.png|right|]] Open the [[NeoScan]] Optical Bench Manager program. The [[NeoScan]] Optical Bench Manager program is a Labview-Based System Operation which monitors the system status and the total return and polarization optical powers (see section 3.1 for more details). It is accessible through the desktop or Windows Explorer by double clicking on NeoScanOBM icon [[Image:icon_OBMicon_OBM_small.png]] as shown in Figure 2.7. The program will start running as shown in Figure 2.8.</p>

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<center>[[Image:neoscanfig_2_7.png|thumb|rightcenter|500px|<i><b>Figure 2.7</b>: NeoScan Program Group in or Windows Explorer.</i>]] </center> When the program starts, the system should detect the total return power and polarization power and display their graphs over time and show their numerical values in mW, see Figure 2.8. The green “Probe Detected” indicator light will indicate that the probe is connected to the correct channel. Otherwise, if either the total return power or the polarization power is too low (less than 0.3 mW), the information panel will remind the users to correct the problem. This can be the case if the probe is not connected or is defective or there is a problem with the [[NeoScan]] system (Figure 2.9). Select the channel number you want to check using the dropdown list labeled “Select Channel.”

[[Image:neoscanfig_2_8.png|thumb|center|600px650px|<i><b>Figure 2.8</b>: The total return power and polarization power of delivered beam to optical probe.</i>]]

[[Image:neoscanfig_2_9.png|thumb|center|600px650px|<i><b>Figure 2.199</b>: NeoScan Optical Bench Manager indicating that the total return power is too low.</i>]]

<ol><li> <p>Set up the 2-axis translation stage on a stable flat table, an optical table is preferred.</p></li><li> <p>Mount the plastic probe fixtures on the Z linear translation stage using the screw,.</p></li><li> <p>Loosen all screws of the cubic probe holder. Lift the cap and rest the probe holder on a flat horizontal flat surface. Gently insert the probe into the gap in the plastic probe holder in such a way that that about 0.6” (1.5cm) of the probe comes out from the either ends of the gap (Figure 2.11).</p></li><li> <p>While the probe is sitting inside the gap, place the cap on the probe holder and secure it by fastening the four plastic screws. Make sure it is tight is enough so that the probe does not slip out of the gap. Yet, do not tighten hard since it may break the probe glass. Tighten the screws until you feel that you are not able to rotate the probe by your fingers.</p></li><li> <p>Place the cube holder inside the probe fixture head in such a way that the probe passes through the existing hole (Figure 2.12). Make sure the probe does not hit the edges of the hole, otherwise, it may break and the crystal may fall off.</p></li><li> <p>To avoid bending the soft plastic shield of the fiber, pass the fiber through the top of the probe fixture using regular (Scotch) adhesive tapes as shown in Figure 2.13.</p> <p>Important: When pulling out the probe from the hole, make sure the probe is positioned vertically and the probe tip does not touch the edges of the hole.</p></li></ol> <center>[[Image:neoscanfig_2_11.png|thumb|center|650px|<i><b>Figure 2.11</b>: Placing the probe inside the probe holder.</i>]]<br>[[Image:neoscanfig_2_12.png|thumb|center|650px|<i><b>Figure 2.12</b>: Inserting the probe holder inside the probe fixture head.</i>]]</center>