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Polaris® Side Optic Retention Mount for Ø1.50" Optics

  • Designed for Long-Term Stability
  • Matched Actuator/Body Threading Minimizes Drift and Backlash
  • Minimal Temperature-Dependent Hysteresis
  • Sapphire Adjuster Seats Prevent Wear Over Time


Ø1.50" Mirror Mount

Application Idea

Ø1.50" Mount with POLARIS-N5 Removable Adjuster Knobs on a Ø25 mm Post for Polaris Mounts

US Patent 10,101,559

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  • Machined from Heat-Treated Stainless Steel with Low Coefficients of Thermal Expansion (CTE)
  • Hardened Stainless Steel Ball Contacts with Sapphire Seats for Durability and Smooth Movement
  • Matched Actuator and Back Plate Provide Stability and Smooth Kinematic Adjustment
  • Passivated Stainless Steel Surface Ideal for Vacuum and High-Power Laser Cavity Applications
  • Custom Mount Configurations are Available by Contacting Tech Support
  • Patented Optic Bore Design with Monolithic Flexure Arm

Polaris® Low-Drift Kinematic Mirror Mounts are designed to securely hold Ø1.50" (38.1 mm) optics, such as our low-GDD ultrafast mirrors, and are the ultimate solution for applications requiring stringent long-term alignment stability.

Optic Retention
This Polaris mirror mount features a patented optic bore design with a monolithic flexure arm to hold the optic. This design provides high holding force and pointing stability while allowing quick and easy installation of the optic.

Polaris optic bores are precision machined to achieve a fit that will provide optimum beam pointing stability over changing environmental conditions such as temperature changes, transportation shock, and vibration. Performance will be diminished if the Ø1.50" mount is used with optics that have an outer diameter tolerance greater than +0/-0.1 mm.

Machined from heat-treated stainless steel, Polaris mounts utilize precision-matched adjusters with ball contacts and sapphire seats to provide smooth kinematic adjustment. The Polaris design addresses all of the common causes of beam misalignment; please refer to the Design Features tab for detailed information.

Post Mounting
The Polaris mirror mounts are equipped with #8 (M4) counterbores for post mounting. The Ø1.50" mount also includes Ø2 mm alignment pin holes around the mounting counterbore, allowing for precision alignments when paired with our posts for Polaris mirror mounts. See the Usage Tips tab for more recommendations about mounting configurations.

Cleanroom and Vacuum Compatibility
The POLARIS-K15S4 is designed to be compatible with cleanroom and vacuum applications. See the Specs tab and the Design Features tab for details.

Item # POLARIS-K15S4
Optic Sizea Ø1.50" (38.1 mm)
Optic Thickness (Min) 0.24" (6.0 mm)
Number of Adjusters Two
Adjuster Drive 5/64" Hex, Ø0.07" Side Adjustment Holes
Adjuster Pitch 100 TPI
Actuator Matching Matched Actuator/Body Pairs
Measured Point-to-Point 
Mechanical Resolution per Adjuster
(Bidirectional Repeatability)
5 µrad (Typical); 2 µrad (Achievable)
Adjustment per Revolutionb ~5.5 mrad/rev
Front Plate Translation (Max) N/A
Mechanical Angular Range (Nominal) ±3°
Front Plate Separation at Pivot Adjuster 3.175 mm
Beam Deviationc After Thermal Cycling <1 μrad
Recommended Optic Mounting Torqued 5 - 7 oz-in (0.035 - 0.049 N·m) for 6 mm Thick Optics
Mounting Two #8 (M4) Counterbores
Alignment Pin Holes Two at Each Counterboree
Vacuum Compatibilityf 10-9 Torr at 25 °C with Proper Bake Out
10-5 Torr at 25 °C without Bake Out
Grease Vapor Pressure: 10-13 Torr at 20 °C; 10-5 Torr at 200 °C
Epoxy Meets Low Outgassing Standards NASA ASTM E595, Telcordia GR-1221
Operating Temperature Range -30 to 200 °C
  • For best performance, use optics with a diameter tolerance of up to +0/-0.1 mm.
  • When the front plate is parallel to the back plate.
  • After 12.5 °C temperature cycle, the beam returns to within 1 μrad of its original position for a Polaris mounted on a Ø1" post.
  • The optimal optic mounting torque can vary by ±1 oz-in due to variations in optic diameter and tolerance buildup.
  • Standard DIN 7-m6 ground dowel pins are recommended. The recommended tolerance for the location of the mating dowel pin holes and threaded mounting hole is ±0.003".
  • Vacuum-compatible Polaris mounts are assembled in a clean environment, chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface, and double vacuum bagged. The 8-32 and M4 cap screws included with the Polaris mounts are not rated for pressures below 10-5 Torr. Prior to placing any components in a sensitive vacuum system, a thorough pre-baking in a bake-out oven should be performed to remove all moisture and surface volatiles. Contact Tech Support for details.

Click to Enlarge

Details of the Polaris Side Optic Retention Design

Several common factors typically lead to beam misalignment in an optical setup. These include temperature-induced hysteresis of the mirror's position, crosstalk, drift, and backlash. Polaris mirror mounts are designed specifically to minimize these misalignment factors and thus provide extremely stable performance. 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 kinematic mirror mount.

Thermal Hysteresis
The temperature in most labs is not constant due to factors such as air conditioning, the number of people in the room, and the operating states of equipment. Thus, it is necessary that all mounts used in an alignment-sensitive optical setup be designed to minimize any thermally induced alignment effects. Thermal effects can be minimized by choosing materials with a low coefficient of thermal expansion (CTE), like stainless steel. However, even mounts made from a material with a low CTE do not typically return the mirror to its initial position when the initial temperature is restored. All the critical components of the Polaris mirror mounts are heat treated prior to assembly since this process removes internal stresses that can cause a temperature-dependent hysteresis. As a result, the alignment of the optical system will be restored when the temperature of the mirror mount is returned to the initial temperature.

The method by which the mirror is secured in the mount is another important design factor for the Polaris; this Polaris mount offers excellent performance without the use of adhesives. Instead, it uses a monolithic flexure arm to hold the edge of the optic. The monolithic design is less sensitive to fluctuations in temperature and induces less distortion on the optic surface than a simple setscrew retention design.

Crosstalk is minimized by carefully controlling the dimensional tolerances of the front and back plates of the mount so that the pitch and yaw actuators are orthogonal. In addition, sapphire seats are used at all three contact points of the ball of each actuator. Standard metal-to-metal actuator contact points will wear down over time. The polished sapphire seats of the Polaris mounts, in conjunction with the hardened stainless steel actuator tips, maintain the integrity of the contact surfaces over time.

Drift and Backlash
In order to minimize the positional drift of the mirror mount and backlash, it is necessary to limit the amount of play in the adjuster as well as the amount of lubricant used. When an adjustment is made to the actuator, the lubricant will be squeezed out of some spaces and built up in others. This non-equilibrium distribution of lubricant will slowly relax back into an equilibrium state. However, in doing so, this may cause the position of the front plate of the mount to move. The Polaris mounts use adjusters matched to the body or bushings that exceed all industry standards so very little adjuster lubricant is needed. As a result, alignment of the Polaris mounts is extremely stable even after being adjusted. In addition, these adjusters have a smooth feel that allows the user to make small, repeatable adjustments.

Double Vacuum Bagging for Polaris Mounts
Click to Enlarge

Polaris Mounts are Shipped Inside Two Vacuum Bag Layers

Cleanroom and Vacuum Compatibility
The POLARIS-K15S4 is designed to be compatible with cleanroom and vacuum applications. It is chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface. After passivation, the mount is assembled in a clean environment and double vacuum bagged to eliminate contamination when transported into a cleanroom.

The lighter hatched engraving used in this mount is a pure metal engraving which is fully passivated and chemically cleaned. This results in a pure metal surface that is better suited for high-temperature environments using extremely high-energy sources.

All Polaris mounts have sapphire contacts bonded into place using a NASA-approved low outgassing procedure. In addition, DuPont Krytox® LVP High-Vacuum Grease, an ultra-high-vacuum-compatible, low outgassing PTFE grease, is applied to the adjusters. Please note that the 8-32 and M4 cap screws included with the Polaris mounts are not rated for pressures below 10-5 Torr.

Each vacuum-compatible Polaris mount is packaged within two vacuum bag layers after assembly in a clean environment, as seen in the image to the right. These vacuum bags do not contain any desiccant materials and tightly wrap the mount, preventing friction against the mount during shipping. This packing method protects the mount from corrosion, gas or liquid contamination, and particulates during transport. The first vacuum bag should be opened in a clean environment while the second vacuum bag should only be opened just prior to installation. When operating at pressures below 10-5 Torr, we highly recommend using an appropriate bake out procedure prior to installing the mount in order to minimize contamination caused by outgassing.

Polaris 1/2" mounted on 1" post
Click to Enlarge
A POLARIS-K05 mounted to a surface using a Ø1" Post for Polaris Mirror Mounts and a Polaris Clamping Arm. Using a 1.50" long post, the optical axis is 2.0" above the table surface.
Back of Polaris Mount Shown on Breadboard
Click to Enlarge

POLARIS-K1 Mounted Directly to Breadboard using 1/4"-20 to 8-32 Adapter

Through thermal changes and vibrations, the Polaris kinematic mirror mounts are designed to provide years of use. Below are some usage tips to ensure that the mount provides optimal performance.

Match Materials
Due to its relatively low coefficient of thermal expansion, stainless steel was chosen as the material from which to fabricate the front and back plates of the Polaris mounts. When mounting, we recommend using components fabricated from the same material, such as our Ø25 mm Posts for Polaris Mirror Mounts and Polaris Clamping Arm.

Use a Wide Post
The Polaris' performance is optimized for use with our Ø25 mm Posts and our non-bridging clamping arms. These posts are made of stainless steel and provide two lines of contact with the mount, which help confine the bottom of the mount during variations in the surrounding temperature, thereby minimizing potential alignment issues.

Optic Mounting
Since an optic is prone to movement within its mounting bore, all optics should be mounted with the Polaris out of the setup to ensure accurate mounting that will minimize misalignment effects. We recommend using a torque wrench when installing an optic in the Polaris mounts. Over torquing the flexure-spring optic retainer can result in dramatic surface distortions.

Front Plate’s Position
The Ø25 mm Polaris mount is designed to allow adjustments of up to 8°. To achieve the best performance, it is recommended that the front plate be kept as close to parallel to the back plate as possible. This ensures the highest stability of the adjustments.

Mount as Close to the Table’s Surface as Possible
To minimize the impact of vibrations and temperature changes, it is recommended that your setup has as low of a profile as possible. Using short posts will reduce the Y-axis translation caused by temperature variations and will minimize any movements caused by vibrations. Mount the Polaris directly onto a flat surface such as a breadboard using a 1/4"-20 to 8-32 thread adapter (AE8E25E) or M6 x 1.0 to M4 x 0.7 adapter (AE4M6M). By doing so, the instability introduced by a post will be eliminated. For direct mounting, knobs cannot be used on bottom adjusters, as shown in the photo to the right.

Polish and Clean the Points of Contact
We highly recommend that the points of contact between the mount and the post, as well as the post and the table, are clean and free of scratches or defects. For best results, we recommend using a polishing stone to clean the table’s surface and a LFG1P polishing pad for the top and bottom of the post as well as the bottom of the mount.

Use Polaris-Specific Adjustment Tools
We offer stainless steel knobs for most of our Polaris adjusters, either included with the mount or available separately. For Polaris mounts with side hole adjusters, we recommend using the SA1 Side Hole Adjustment Tool, which features a precision-fit tip designed for the side holes to allow backlash-free adjustment. The stainless steel material is chemically cleaned for use in clean setups. For securing adjuster lock nuts on these Polaris mounts, we recommend using the TW13 torque wrench below, which is designed to ensure proper torque is applied to the lock nuts for long-term locking. These wrenches are chemically cleaned and compatible with cleanroom and vacuum chamber applications.

Not Recommended
We do not recommend taking the adjusters out of the back plate, as it can contaminate the threading. This can reduce the fine adjustment performance significantly. Also, do not pull the front plate away as it might stretch the springs beyond their operating range or crack the sapphire seats. Finally, do not over tighten the setscrew on the monolithic optic retention arm; only slight force is required to secure the optic in place.

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Polaris Mount Optic Retention Methods (Click Image to Enlarge)
Side Lock SM Threaded Low Distortion Glue In
Polaris Mount Adjuster Types (Click Image for Details)
Side Hole Hex Adjuster Knobs Adjuster
Lock Nuts
Piezo Adjusters

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.

Polaris Mounts for Ø1/2" Optics 

Polaris Mounts for Ø19 mm (3/4") Optics

Polaris Mounts for Ø25 mm Optics

Polaris Mounts for Ø1" Optics

Polaris Mounts for Ø1.5" Optics

Polaris Mounts for Ø50 mm Optics

Polaris Mounts for Ø2" Optics

Polaris Mounts for Ø3" Optics

Polaris Kinematic Platform Mount

Polaris® Ø1.50" Kinematic Mirror Mount, 2 Adjusters

Click to Enlarge

Methods of Adjusting the POLARIS-K15S4 Ø1.50" Mount:
A: 5/64" or 2.0 mm Hex Key in the End of the Adjuster
B: SA1 Tool Through Adjuster Side Holes
C: POLARIS-N5 Removable Knobs on the Adjuster
D: HKTS-5/64 Hex Knobs with 1/16" or 1.5 mm Balldriver Through Side Hole for Fine Adjustment
  • 2 Hex Adjusters with Side Holes (See Image to the Right)
  • Designed for use with Ø1.50" (38.1 mm) Optics
  • 100 TPI Matched Actuator/Body Pairs
  • ±3° Mechanical Angular Range
  • ~5.5 mrad/rev Resolution
  • Less than 1 µrad Deviation after Temperature Cycling
  • Monolithic Flexure Arm for Minimal Optic Distortion and Improved Optic Holding Stability

This 2-adjuster Ø1.50" Polaris Kinematic Mirror Mount is designed to provide easy high-resolution adjustment and long-term alignment stability. The mount features a monolithic flexure arm that can be actuated using the included screw and a 0.05" (1.3 mm) hex key. The monolithic flexure arm design keeps wavefront distortion on the mounted optic to a minimum while providing an optic retention force that is much stronger than the force provided by a standard setscrew mount. The 2-adjuster design improves mount stability by limiting the available degrees of freedom for movement. The monolithic front plate and stiffer springs used in the construction of this mount provide enhanced stability and make it an ideal solution for OEM applications that require reliable operation in rugged environments.

The 100 TPI adjusters feature three Ø0.07" through holes that allow for actuation from the side using our precision-fit SA1 Side Hole Adjustment Tool (sold below) or a 1/16" (1.5 mm) balldriver or hex key. Each adjuster also has a 5/64" (2.0 mm) hex and may be adjusted with the hex on the end of the SA1, our HKTS-5/64 Hex Key Thumbscrews (sold below), or any other 5/64" (2.0 mm) hex wrench. Alternatively, POLARIS-N5 removable, low-profile adjustment knobs (sold below) can be threaded onto the adjusters for improved feel in fine-resolution adjustments; note that the removable knobs will block the adjuster side holes but not the hex. The adjusters on this mount can be locked using the POLARIS-LN1 lock nuts (sold separately below). For applications that require frequent tuning of the adjusters, the lock nuts only need to be lightly tightened to a torque of approximately 4 to 8 oz-in (0.03 to 0.06 N·m). For long term stability, we recommend tightening to a torque of 32 oz-in, which can be achieved by using our TW13 preset torque wrench (sold below). 

Post mounting is provided by two #8 (M4) counterbores. For custom mounting configurations, two Ø2 mm alignment pin holes are located on each mounting face for setting a precise location and mounting angle. Standard DIN 7-m6 ground dowel pins are recommended (click on the red documents icon below for details).

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
POLARIS-K15S4 Support Documentation
POLARIS-K15S4Polaris® Ø1.50" Mirror Mount, 2 Hex Adjusters with Side Holes

Removable Knob for 1/4"-100 Adjusters

Click to Enlarge

POLARIS-K1C4 Mount with Optic and Optional POLARIS-N5 Removable Knobs
  • For Convenient Adjustment of 1/4"-100 Adjusters
  • Attaches Directly to Adjuster Threading
  • Sold Individually

The Polaris® Removable Knobs for 1/4"-100 Adjusters allows the user to adjust a Polaris kinematic mirror mount by hand. The knobs can be used with select Polaris mounts, listed in the table to the right. Note that when the knobs are used with any of these mounts, they will block the side through holes on the adjuster. The adjuster screw's 5/64" (2 mm) hex socket is still usable when the knobs are attached.

POLARIS-K1C4 and POLARIS-K1S4 Mounts purchased before September 21, 2016 cannot be used with the POLARIS-N5 Removable Knobs sold here.
To order compatible knobs, please contact Tech Support.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
POLARIS-N5 Support Documentation
POLARIS-N5Polaris® Removable Knob for 1/4"-100 Adjusters with Side Holes, Qty. 1

5/64" Hex Key Adjusters

POLARIS-K12AH with HKTS-5/64 Adjuster
Click for Details

POLARIS-K1-2AH with HKTS-5/64 Adjuster
  • For Convenient Adjustment of 5/64" and 2 mm Hex-Driven Actuators
  • Red Anodized Adjustment Knob with Engraved Hex Size
  • Replaceable Hex Tip
  • Sold in Packages of 4

These 5/64" Hex Key Adjuster Thumbscrews allow for quick adjustment of many 5/64" and 2 mm hex-driven actuators (or standard actuators with the knobs removed). These temporary knobs can be left in the screw's hex socket between adjustments for convenience (see photo to the right). An 8-32 setscrew (5/64" hex) secures the replaceable hex bit, which can be reversed if the tip is stripped. Contact Tech Support to order replacement hex key bits.

We offer hex key thumbscrews in sizes from 0.050" to 3/16" and 2 mm to 5 mm.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
HKTS-5/64 Support Documentation
HKTS-5/64Customer Inspired! 5/64" (2 mm) Hex Key Thumbscrew, 4 Pack

Side Hole Adjustment Tool for Polaris Mounts

Click to Enlarge

The SA1 Adjusting a POLARIS-K1S4 Using the Side Holes and Rear Hex
  • Ø0.07" Precision-Fit Tip for Side Holes on Polaris Adjusters
  • 5/64" (2.0 mm) Hex on Handle
  • Magnetic, Chemically Cleaned Stainless Steel

The Side Hole Adjustment Tool features a Ø0.07" precision-fit tip designed for Polaris mounts with side hole adjusters. The handle features a 5/64" (2.0 mm) hex allowing the SA1 to act as a small knob, and the central nut is compatible with a 6.0 mm wrench allowing for a longer lever arm. The precision-fit tip minimizes backlash during adjustments and the depth stop allows the tool to rest securely in a side hole between adjustments. On Ø25 mm mirror mounts and larger, the 1.62" length allows the tool to adjust the actuator 360° without interfering with the other adjuster on the back of the mount.

The SA1 is made of chemically cleaned, hardened, super alloy stainless steel for durability and compatibility with clean environments. The tool is also magnetic allowing it to be easily retrieved from tight or sensitive setups using a magnet. 

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
SA1 Support Documentation
SA1Customer Inspired! Side Hole Adjustment Tool for Polaris Mounts, Ø0.07" Tip, 5/64" (2.0 mm) Hex

1/4"-100 Adjuster Lock Nuts for Polaris Mounts

To install a lock nut without cross threading, gently place the lock nut against the end of the adjuster. "Unscrew" the nut until the threads of the nut and the adjuster align before threading the nut onto the adjuster. This animation shows the installation of a POLARIS-LN1 lock nut on a POLARIS-K1F1 low distortion mount.

  • Provide Long Term Adjuster Stability
  • Compatible with Select Polaris Mounts

These lock nuts are designed for use with our Polaris mounts with 1/4"-100 adjusters. Designed for long-term adjuster stability or applications that are exposed to shock and vibration, these lock nuts are pre-greased with the same ultra-high-vacuum-compatible, low-outgassing PTFE grease as the Polaris mounts and have been tested for adjuster fit.

For applications that require frequent tuning of the adjusters, the lock nuts only need to be lightly tightened by hand to a torque of approximately 4 to 8 oz-in (0.03 to 0.06 N·m). For long term stability, we recommend tightening to a torque of 32 oz-in, which can be achieved by using our TW13 preset torque wrench (sold below). POLARIS-LN1 lock nuts have a 13 mm hex. To avoid cross threading the lock nut, place it against the adjuster and "unscrew" the lock nut until you feel a slight drop; then thread the lock nut onto the adjuster.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
POLARIS-LN1 Support Documentation
POLARIS-LN11/4"-100 Lock Nut, 13 mm Hex, Stainless Steel

Torque Wrench for Polaris Lock Nuts

Coaxial Connector Wrench
Click to Enlarge

TW13 Torque Wrench Used to Secure POLARIS-LN1 Lock Nut on POLARIS-K2S2 Mirror Mount
Coaxial Connector Wrench
Click to Enlarge

The TW13 wrench is engraved with its preset torque value and item #.
  • 13 mm Hex for Use with POLARIS-LN1 and POLARIS-LN4 Lock Nuts
  • Preset Torque Value of 32 oz-in (0.23 N•m)
  • Break-Over Design Ensures Proper Torque is Applied
  • Ideal for Applications Requiring Long-Term Locking

This torque wrench has a preset torque value of 32 oz-in for use with the
POLARIS-LN1 and POLARIS-LN4 lock nuts used on Polaris® mounts. When the preset torque value has been achieved, the break-over design will cause the pivoting joint to "break," as shown to the right. The wrench's hex head will move back into place once the force is removed. This design prevents further force from being applied to the lock nut. Engraved guidelines indicate the angle the wrench should pivot in order to apply the specified torque; pivoting the handle past these guidelines will over-torque the lock nut. The wrench is also engraved with its preset torque value, torque direction, wrench size, and item # for easy identification in the field.

This wrench is designed to be compatible with cleanroom and vacuum chamber applications. It is chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface. After passivation, it is assembled in a clean environment and double vacuum bagged to eliminate contamination when transported into a cleanroom. The wrench has a bead blasted finish to minimize reflections when working with setups that include lasers.

Please note that these wrenches are not intended for use in applications where adjusters are frequently tuned, as these applications typically require torque values of 4 to 8 oz-in (0.03 to 0.06 N·m).

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
TW13 Support Documentation
TW13Customer Inspired! 13 mm Preset Torque Wrench for Polaris Lock Nuts, 32 oz-in
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