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Polaris® Fixed Monolithic Mirror Mount for Laser System Design![]()
Heat-Treated, Monolithic Stainless Steel Precision Alignment Bore
POLARIS-19S50/M For Ø19 mm Mirrors (Mirror Sold Separately)
FRONT BACK Flexure Arm Optic Retention
POLARIS-CA1 Non-Bridging Clamping Arm
![]() Please Wait Features
Monolithic Construction Designed for Ø19 mm Optics ![]() Click to Enlarge The flexure arm used in the Polaris mount provides stable optic retention with minimal wavefront distortion. Please see the Test Data tab for test results. Flexure Arm for Optic Retention Polaris lens cells are precision machined to achieve a fit that will provide optimum beam pointing stability performance over changing environmental conditions such as temperature changes, transportation shock and vibration. These mounts have had their performance tested and verified with Ø19 mm optics that have a diameter tolerance of up to +0/-0.1 mm, so this tolerance range is recommended for optimal performance. Note that the mounts are not intended for use with optics that have an outer diameter tolerance greater than zero. Non-Bridging Clamping Arm Mounting Features In combination with our cage rods, the Ø6 mm +0.025/-0.000 mm precision bore in the Polaris fixed mount allows for the alignment of multiple mounts along a common optical axis, or for fine angle tuning when used with our POLARIS-CA1(/M). Please see the Usage Tips tab for more information and other usage recommendations. Cleanroom and Vacuum Compatibility
Vacuum Compatible and Low Outgassing ![]() Click to Enlarge All Polaris Mounts are Shipped Inside Two Vacuum Bag Layers ![]() POLARIS-19S50/M Mechanical Drawing Ø19 mm OpticsThe POLARIS-19S50/M is designed to securely hold 6 mm thick, Ø19 mm mirrors. This mirror size allows the mounts to maintain a Ø1" footprint while maximizing the clear aperture of the mirror face. The flexure arm and setscrew combination provide three points of axial contact to minimize distortion as well as increasing the holding force and stability of the optic. Thorlabs stocks a wide variety of Ø19 mm mirrors for use with our POLARIS-19S50/M Fixed Monolithic Mirror Mount. This includes broadboad dielectric, laser line, metallic, and blank mirrors. See the table below for all of our stocked options.
Polaris® Mirror Mounts Test DataPolaris Fixed Monolithic Mirror Mounts have undergone extensive testing to ensure high-quality performance.
Optical Distortion Testing Using a ZYGO Phase-Shifting InterferometerStress, strain, and displacement are all typical mounting forces experienced by an optic in any mount. Stress is the sum of all internal forces acting on a deformable object, strain is a measurement of deformation, and displacement is a measurement of how the stress and strain affect the shape and position of the object. Minimizing this effect is crucial; any distortion to the optic is transmitted to the light that is reflected from it. A ZYGO Phase-Shifting Interferometer was used to determine the recommended torque for retaining the optic while minimizing wavefront distortion. The results of these tests can be found below. Based on these tests, we recommend a torque of 5.5 - 6 oz-in for the flexure arm. These values provide a typical wavefront distortion of 0.1 waves.
Procedure: Results: ![]() Click to Enlarge 5 oz-in of Torque ![]() Click to Enlarge 5.5 oz-in of Torque ![]() Click to Enlarge 6 oz-in of Torque ![]() Click to Enlarge 6.5 oz-in of Torque ![]() Click to Enlarge 7 oz-in of Torque
Positional Repeatability After Thermal ShockThe Polaris was first secured to a stainless steel rigid platform in a temperature-controlled environment. The mirror is held using the stainless steel flexure arm, not glued; see the Usage Tips tab for additional mounting recommendations. A beam from an independently temperature-stabilized laser diode was reflected by the mirror onto a position sensing detector. Purpose: This testing was done to determine how reliably the mount returns the mirror, without hysteresis, to its initial position. These measurements show that the alignment of the optical system is unaffected by the temperature shock. Procedure: The temperature of each mirror mount tested was raised to 37.5 °C. The elevated temperature was maintained for 60 minutes (soak time). Then the temperature of the mirror mount was returned to the starting temperature. Each POLARIS-19S50/M was clamped to the table using the POLARIS-CA1 Clamping Arm. The results of these tests are shown below. Results: As can be seen in the plots below, when the Polaris mounts were returned to their initial temperature, the angular position (both pitch and yaw) of the mirrors returned to within 2 µrad of its initial position. The performance of the Polaris was tested further by subjecting the mount to repeated temperature change cycles. After each cycle, the mirror’s position reliably returned to within 2 µrad of its initial position. Conclusions: The Polaris Fixed Monolithic Mirror Mount is a high-quality, ultra-stable mount that will reliably return a mirror to its original position after cycling through a temperature change. As a result, the Polaris mount is ideal for use in applications that require long-term alignment stability. ![]() Click to Enlarge The plot above shows the pitch and yaw measured by a position-sensing detector before, while, and after a thermal shock was applied to the POLARIS-19S50/M mount.
Optical Distortion Testing Using a ZYGO Phase-Shifting InterferometerStress, strain, and displacement are all typical mounting forces experienced by an optic in any mount. Stress is the sum of all internal forces acting on a deformable object, strain is a measurement of deformation, and displacement is a measurement of how the stress and strain affect the shape and position of the object. Minimizing this effect is crucial; any distortion to the optic is transmitted to the light that is reflected from it. A ZYGO Phase-Shifting Interferometer was used to determine the recommended torque for retaining the optic while minimizing wavefront distortion. The results of these tests can be found below. Based on these tests, we recommend a torque of 5.5 - 6 oz-in for the flexure arm. These values provide a typical wavefront distortion of 0.1 waves.
![]() Click to Enlarge Figure 1 Laser Platform DeformationPurpose: This testing was performed to determine the extent to which an industry-standard clamping fork deforms or permanently damages a stainless steel rigid platform and whether or not the POLARIS-CA1(/M) improves upon or prevents this damage. These measurements show that the POLARIS-CA1(/M) significantly reduce temporary deformation to the surface and that no permanent damage was measured during our extensive tests. Procedure: An industry-standard clamping fork was mounted in close proximity to another optical element that was used for aligning a beam onto a position detector. As the clamping fork was mounted to the platform at various torque values (blue data sets in Figure 1 and Figure 2), the yaw and pitch deviation of the beam was measured at the detector. At 75 in-lbs of torque the fork was left attached to the platform for 16 hours. After the 16 hour period, the fork was released from the table and the final beam deviation was recorded (red data sets in Figure 1 and Figure 2). This procedure was repeated for the POLARIS-CA1 Clamping Arm. Each test was performed at different regions of the platform. If the final deviation is anything but zero, then the surface has been permanently deformed. Results: As can be seen in the plots below and to the right, the industry-standard clamping fork created a yaw and pitch deviation of 131 µrad and 702 µrad, respectively, at 75 in-lbs, while the POLARIS-CA1 Clamping Arm created a yaw and pitch deviation of 12.2 µrad and 61 µrad, respectively, at 75 in-lbs. The POLARIS-CA1 also returned the beam to its initial position when released after a 16 hour hold. The industry-standard clamping fork did not return the beam to its original position; the beam stayed at a yaw and pitch deviation of 176 µrad and 321 µrad, respectively. The simulaton results shown in Figures 3 and 4 show the amount of deformation created by an industry-standard clamping fork compared to the POLARIS-CA1 clamping arm. Conclusion: The POLARIS-CA1 Clamping Arm caused no permanent damage to the optical mounting surface and it significantly minimized the deformation to the platform surface when it was in use (see Figures 3 and 4). The industry-standard clamping fork was shown to permanently damage the laser platform after use, and to create severe deformation to the surface while in use. As a result, the Polaris clamping arm is ideal for use in systems requiring long term stability and consistent, precision alignments. ![]() Click for Details Figure 2 Note that the distortion caused by the Polaris clamping arm at 75 in-lb is comparable to the distortion caused by the industry-standard clamping fork at 10 in-lb. ![]() Click to Enlarge Figure 4 In comparison, the POLARIS-CA1 causes minimal deformations around the fork. Note that the scale on this second plot has been magnified by 10X in order to make these minimal deformations visible. ![]() Click to Enlarge Figure 3 The industry-standard clamping fork causes large deformations over a significant area surrounding the fork.
Mounting TorquePurpose: This testing was performed to determine the ideal amount of clamping torque necessary to (1) securely mount a Ø1" post within the flexure clamp bore of the POLARIS-CA1(/M) clamping arm, and (2) to secure the clamping arm into a laser system. This data was then compared to the closest competitor's industry-standard clamping fork design. Procedure: The POLARIS-CA1(/M) was used to hold a standard Ø1" post. The clamping arm was first bolted to the stainless steel rigid platform and the flexure clamp was actuated, using the side-located 1/4"-20 (M6) cap screw, to specific torque values. At each specific torque value of the flexure clamp, the post had a rotational torque applied around its axis until it moved within the fork's bore. The torque value at the moment directly before this "movement point" is called the holding torque (see plots below). A similar test was then applied to find the ideal torque need to secure the clamping arm to the laser platform. Results: As can be seen in Figures 5 - 10 below, the POLARIS-CA1(/M) flexure clamp had higher holding torque at a lower clamping torque when compared to the closest competitor's design. At 20 in-lbs of clamping torque, the POLARIS-CA1 provided 110 in-lb of holding torque, while at the same clamping torque, the competitor's fork only achieved a holding torque of 25 in-lbs. For reference, 110 in-lbs of torque is enough to damage the threading on a 1/4"-20 stainless steel cap screw. The corresponding torque for the POLARIS-CA1/M is a holding torque of 12.4 N•m at a clamping torque of 2.4 N•m. The scales for these measurements, as seen in Figures 6 and 8 below, are not a direct conversion due to an efficiency difference between 1/4"-20 and M6 screws. The efficiency of M6 screws is about 5% less than that of 1/4"-20 screws due to differences in diameter and pitch. The recommended torque for the mounting slot (Figure 8) varies depending upon the position where a 1/4"-20 (M6) cap screw is secured into the slot (i.e. close to the post, midway along the slot, or far from the post). The performance of the closest competitor's clamping fork (see Figure 9) is also dependent on the position where the 1/4"-20 (M6) cap screw is secured into the slot. However, the performance of the fork degrades sharply at the mid and far positions, as seen in Figure 9. At the far position, the best holding torque achieved is 32 in-lb with a clamping force of 70 in-lb. Conclusion: The POLARIS-CA1(/M) was shown to be the ideal solution for securely mounting a component to a laser system platform. At only 20 in-lb and 40 in-lb of clamping torque for the flexure clamp and slot mounting respectively, the post mounted in a POLARIS-CA1 can withstand up to 110 in-lb of opposing torque (corresponding torques for the POLARIS-CA1/M are 2.4, 4.8, and 12.4 N•m, respectively). This performance is superior to the closest competitor's industry-standard clamping fork, which needs a clamping force of 70 in-lb in the close position to reach a similar value of 100 in-lb. Minimizing the amount of torque applied to the mounting surface prevents permanent damage. ![]() Click to Enlarge Figure 9 Results from Test 2 on a competitor's clamping fork. See Figure 8 above for results from POLARIS-CA1(/M). ![]() Click to Enlarge Figure 10 Comparison of Test 2 results for POLARIS-CA1 and a competitor's clamping fork, both at the middle position in the moutning slot. Hours of extensive research, multiple design efforts using sophisticated design tools, and months of rigorous testing went into choosing the best components to provide an ideal solution for experiments requiring ultra-stable performance from a fixed mirror mount. Thermal Hysteresis Optic Retention ![]() Click to Enlarge At zero torque, the sample mirror's flatness was λ/20 over the clear aperture (λ = 633 nm). The shaded region in this plot denotes the recommended optic mounting torque for a 6 mm thick optic. Through thermal changes and vibrations, the Polaris™ fixed mirror mount is designed to provide years of use. Below are some usage tips to ensure that the mount provides optimal performance. Monolithic Design Ø6 mm Precision Bore ![]() Click to Enlarge The Ø6 mm Precision Bore can be Used with a Cage Rod to Align Two or More Fixed Polaris Mounts ![]() Click to Enlarge A cage rod can be used for fine angle tuning in combination with the precision bore and a POLARIS-CA1 Clamping Arm (all items sold separately). Optic Mounting Extensive testing was also performed to see the performance when the flexure clamp is hand tightened without a torque wrench. The results of this test can be found here. When hand-tightening the flexure arm to retain the optic, sufficient torque should be applied to feel the contact between the arm and optic. Once that is achieved, the optic will be secured within the cell. Though this method is repeatable and will maintain low optic distortion, we recommend using a torque wrench for the best results. Do not actuate the flexure arm without an optic installed. The POLARIS-19S50/M mount is calibrated to minimize mirror distortion at 5.5 - 6 oz-in of optic mounting torque; if the flexure arm is forced beyond the point when it would normally contact the optic, this calibration will no longer be valid. Installing the post in the clamping arm before attaching the clamping arm to the table can create a bridge, which can alter optical alignment and damage the surface of the optical table or breadboard. Mount as Close to the Platform Surface as Possible Attach the Clamping Arm to the Table First Polish and Clean the Points of Contact
Thorlabs offers several different general varieties of Polaris mounts, including kinematic side optic retention, SM-threaded, low optic distortion, piezo-actuated, and glue-in optic mounts, as well as a fixed monolithic mirror mount and fixed optic mounts. Click to expand the tables below and see our complete line of Polaris mounts, listed by optic bore size, and then arranged by optic retention method and adjuster type. We also offer a line of accessories that have been specifically designed for use with our Polaris mounts; these are listed in the table immediately below. If your application requires a mirror mount design that is not available below, please contact Tech Support.
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![]() ![]() Click to Enlarge POLARIS-CA1/M Holding Torque Results* The Polaris clamping fork design has undergone extensive testing to ensure high-quality performance. See the Clamping Arm Data tab for additional test results. *It is important to note that the 1/4"-20 and M6 x 1.0 clamping torque values have been adjusted to provide the same clamping post and table forces. Also note that the maximum recommended tightening torque for an 18-8 stainless steel screw is 75.2 in-lbs for a ¼-20 screw and 8.8 N-m for an M6 x 1.0 screw. Higher mounting torques can cause the screw to fail. ![]() Click to Enlarge Side-Located 1/4"-20 (M6) Screw Actuates Clamping Bore
The Polaris Clamping Arm is the ideal solution for stably mounting any Ø1" post. Each clamping arm, which is constructed from heat-treated, stress-relieved stainless steel, provides extremely high holding forces with minimal torquing of the mounting screws. The POLARIS-CA1 and POLARIS-CA1/M are designed to hold a Ø1" post, such as the fixed Polaris mount above, using a flexure clamping mechanism. They are not compatible with Ø25 mm posts; the bore diameter is too large and will not contact the post when clamping. The side-located clamping mechanism, as shown in the photo to the above left, is actuated using a 1/4"-20 cap screw for the POLARIS-CA1 or an M6 x 1.0 cap screw for the POLARIS-CA1/M. Because the side-located clamp and mounting slot are tightened separately, the user can set the position of the fork and adjust the rotational alignment independently. The clamping arm has a compact 3.33" x 1.60" (84.5 mm x 40.6 mm) footprint for tight laser cavity setups, with a thickness of 0.60" (15.2 mm) for increased stability. A 1.30" (33.0 mm) long clearance slot allows for a variety of mounting solutions using a 1/4"-20 or M6 x 1.0 cap screw and washer. All clamping arms have been tested for holding strength. Based on the test results, recommended torques have been determined for both the flexure clamp and for tightening the slot to the table. The scales for these measurements, as seen in the figure above, are not a direct conversion due to an efficiency difference between 1/4"-20 and M6 x 1.0 screws. The efficiency of M6 x 1.0 screws is about 5% less than that of 1/4"-20 screws due to differences in diameter and pitch. For optimal performance we recommend tightening this screw of the POLARIS-CA1 with 15 to 25 in-lb of torque and the screw of the POLARIS-CA1/M with 1.75 to 3 N•m of torque. When mounting the clamping arm to the platform we recommend using 40 to 65 in-lb of torque for the POLARIS-CA1 and 4.75 to 7 N•m of torque for the POLARIS-CA1/M. For best results, use the maximum recommended torques from each range. These torque values can be dialed in using a torque driver. The flat, non-bridging (see drawing below) top and bottom allow the clamping arm to be used on either side depending on the needs of the application. This allows optical components to be placed in near contact to one another while minimizing the footprint, as shown in the image to the bottom right. A relief cut is included around the top and bottom slot; this protects the ±0.001" (±0.02 mm) flat surface that contacts the optical table from any marring due to the screw and washer. Minimizing damage to this surface of the fork allows for more stable mounting of components using the clamping arm. Note: The POLARIS-CA1 requires a 3/16" hex key while the POLARIS-CA1/M requires a 5 mm hex key (not included). ![]() Click to Enlarge The Top and Bottom of the Fork can be Used for Mounting, Minimizing the Overall Footprint and Distance Between Components | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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