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Off-Axis Parabolic Mirrors, Acute Angles, Protected Gold Coating (0.8 - 20 µm)
Ø2" Off-Axis Parabolic Mirror in a KS2 Mirror Mount
Ø1", RFL = 2",
Ø2", RFL = 10",
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All of our off-axis parabolic mirrors are made in house and finished on our single-point diamond turning machine. Visit our Custom Mirrors tab for more information.
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Thorlabs' Off-Axis Parabolic (OAP) Mirrors are mirrors whose reflective surfaces are segments of a parent parabolic mirror. They achromatically focus a collimated beam or collimate a broadband divergent source, and their off-axis design spatially separates the focal point from the rest of the beam path. The all-reflective design eliminates phase delays and absorption losses introduced by transmissive optics and makes them well suited for use with femtosecond pulsed lasers.
The geometry of our OAP mirrors is shown to the left. The angle (θ) between the focused beam and the collimated beam is called the "off-axis angle". The OAP mirrors on this page have off-axis angles of 15°, 30°, 45°, or 60°. As shown to the right, the propagation axis of the collimated beam should be normal to the bottom of the substrate to achieve a proper focus. The OAP mirrors sold here are fabricated using aluminum substrates, and the diamond-turned parabolic surface has a protected gold coating that provides >96% average reflectance from 800 nm - 20 µm (see the Graphs tab for a plot of the coating performance). The bottom of each mirror has three tapped mounting holes in a triangle pattern and an alignment hole for use with a mounting adapter (see the Mounting Adapters tab for more details). The non-optical surfaces are black anodized and laser engraved with the item number for easy identification.
Excel Spreadsheet with Raw Data for -M01 Protected Gold Coating
The shaded region in the graph denotes the range over which we guarantee the specified reflectance. Please note that the reflectance outside of this band is typical and can vary from lot to lot, especially in out-of-band regions where the reflectance is fluctuating or sloped. The reflectance of our protected gold coating is relatively independent of the angle of incidence.
Excel Spreadsheet with Raw Data for Our Metallic Coatings
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Mounting Adapter Installation
We offer three types of mounting plates for Ø1" and Ø2" OAP mirrors. The first type is designed to be mounted in any Ø1", Ø2", or Ø3" mirror mount, depending upon the diameter of the OAP mirror. The second type, designed for post mounting, contains an 8-32 (M4) tapped hole on all four sides for direct mechanical compatibility with Ø1/2" Posts. The third type is externally SM threaded for direct compatibility with any of our internally SM-threaded components, such as our rotation mounts.
Our Ø1" and Ø2" OAP mirrors can also be adapted to our SM threads by placing them into our SM Thread to Double Bore Adapters. This adapter allows rotation of the OAP mirror with respect to the adapter prior to securing its position, whereas when using the SM-threaded adapters offered on this page, the final location of the OAP mirror is dictated either by the threads themselves (when fully threaded into a mount) or by using the provided retaining ring to secure it in place.
For Ø3" OAP mirrors, we offer the SM2MP3 mounting adapter, which contains four 8-32 (M4) tapped holes for post mounting and has external SM2 threading for mounting on our SM2-threaded component, such as our K6X2 6-axis kinematic mount.
Alternatively, all of our OAP mirrors may be directly mounted in our Precision Kinematic Mirror Mounts using their outer diameter.
Selecting a Mirror Based on Desired Output Beam Diameter
When using an off-axis parabolic mirror to collimate a divergent source, selection of the appropriate mirror is often done based on the desired output beam diameter. Beam diameter can be calculated very easily using the divergence half-angle of the incident light (Θ) and the reflected focal length of the OAP mirror. To calculate the beam diameter in the small angle approximation, use the following equation:
Beam Diameter = 2 x sin(Θ) x Reflected Focal Length
If you are collimating from a fiber, the equation can be rewritten as:
Beam Diameter = 2 x NA (Fiber) x Reflected Focal Length
The table below lists the output beam diameter as a function of the reflected focal length of the mirror and the divergence half-angle of the incident light. Not listed here is the diameter of the OAP mirror. The clear aperture of the OAP mirror you select should be larger than the desired beam output diameter.
Custom Off-Axis Parabolic (OAP) and Aspheric Mirrors
Thorlabs' advanced single-point diamond turning capabilities allow us to produce custom OAP and aspheric mirrors in small quantities. We can produce long focal length and large diameter optics, as well as optics with custom shapes.
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We offer OAP mirrors with custom sizes, focal lengths, substrates, coatings, and clearance holes.
In addition to our stock off-axis parabolic (OAP) mirrors, Thorlabs is also capable of manufacturing a variety of custom aspheric mirrors. Our unique single-point diamond turning (SPDT) capabilities allow us to produce these customs in low quantities at prices that are comparable with our stock offerings. As shown in the video to the right, we engage the slow-slide-servo process of our SPDT machine to polish individual off-axis mirrors by synchronizing the rotational position of the spindle with the linear position of the translation axes.
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Toroidal mirrors have two different radii of curvature and are used to image off-axis points without introducing astigmatism.
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Conical mirrors provide 360° of illumination.
This unique manufacturing capability allows us to provide OAP mirrors with custom reflected focal lengths and diameters, including long-focal-length and large-diameter optics that cannot be produced by conventional two-axis machining. In addition, we can produce OAP mirrors with a variety of custom substrates (including copper), custom coatings, and custom hole sizes and shapes. The use of copper substrates and other advanced techniques also allow us to offer OAP mirrors with enhanced finishes that exhibit less surface roughness than our our stock products, resulting in improved wavefront quality.
Our SPDT competency also enables us to produce mirrors with other custom biconic surfaces and aspheric shapes, including on-axis parabolic, conical, and toroidal mirrors. These custom mirror shapes can be used in a wide variety of optical instruments and specialized imaging systems. For example, toroidal mirrors, which are used to image off-axis points without introducing astigmatism, are commonly used in compact Czerny-Turner monochromators. Conical mirrors, on the other hand, are ideal for non-imaging applications that require 360° of uniform illumination.
We are generally able to produce custom OAP mirrors and aspheric mirrors with short lead times. For modifications to an existing part, delivery in 4-6 weeks is standard. For custom shapes and long focal length optics, a 6-8 week lead time is typical. To receive more information or a quote for a custom optic, please contact Tech Support.
Our engineers are available to help manufacture optics for your application.
Customs are available in low quantities at prices that are comparable with our stock catalog products.
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|Diametera||1" (25.4 mm)|
|Reflected Focal Length (RFL)a||2" (50.8 mm)||4" (101.6 mm)|
|Parent Focal Lengtha||1.71" (43.4 mm)||3.41" (86.7 mm)|
|Thicknessa||0.86" (21.8 mm)||0.66" (16.8 mm)|
|Reflected Wavefront Error||<λ/4 at 633 nm|
|Bottom Mounting Holesb||Three 4-40 Taps|
|Diametera||2" (50.8 mm)|
|15" (381.0 mm)||10" (254.0 mm)||4" (101.6 mm)||8" (203.2 mm)||4" (101.6 mm)|
|14.74" (374.5 mm)||9.33" (237.0 mm)||3.41" (86.7 mm)||6.83" (173.4 mm)||3.00" (76.2 mm)|
|Thicknessa||0.93" (23.7 mm)||1.01" (25.6 mm)||1.50" (38.0 mm)||1.30" (33.0 mm)||1.82" (46.2 mm)|
|Reflected Wavefront Error||<λ/4 at 633 nm|
|Three 8-32 Taps|
|Diametera||3" (76.2 mm)|
|Reflected Focal Length (RFL)a||6" (152.4 mm)||12" (304.8 mm)|
|Parent Focal Lengtha||5.12" (130.1 mm)||10.24" (260.2 mm)|
|Thicknessa||1.72" (43.6 mm)|
|Reflected Wavefront Error||<λ/2 at 633 nm|
|Bottom Mounting Holes||Three 8-32 Taps|
Our Kinematic Right-Angle Mount and Mounting Adapters for Ø1" Off-Axis Parabolic Mirrors provide mounting alternatives to our smooth bore kinematic mirror mounts. Each offers three #4 counterbores that are positioned to align with the 4-40 tapped holes on our Ø1" OAP mirrors.
The SM1MP OAP Mirror Adapter is externally SM1 threaded (1.035"-40) which allows a Ø1" OAP mirror to be directly mounted to an internally SM1-threaded component. The adapter is designed to allow easy adaptability to a 30 mm cage system as well as SM1-threaded mirror, translation, and rotation mounts. The included SM1RR retaining ring secures the adapter in place when it is threaded into a mount. An SPW606 and a SPW909 or SPW801 Spanner Wrench can be used to thread the retaining ring and adapter, respectively. Three 4-40 cap screws and the required 0.05" hex key are provided with each adapter.
The unthreaded MP254P1 OAP Mirror Adapter is sized to fit inside a Ø2" mirror mount, such as the KS2 Mirror Mount shown above. Three 4-40 cap screws and the required 3/32" hex key are provided with each adapter.
The MP254P2(/M) OAP Mirror Adapter contains four 8-32 (M4) taps for post mounting that orient the OAP mirror at right angles. The distance from the center of the optic to the edge of the mount in the MP254P2 is 1" (25.4 mm), allowing for standardized optical axis heights when used with a fixed height post, such as our Ø1" Posts. Please note that the MP254P2(/M) is not compatible with Ø2" mirror mounts, and is instead designed for post mounting. Three 4-40 cap screws and the required 3/32" hex key are provided with each adapter.
The KCB1P(/M) Right-Angle Kinematic Mount provides ±4° of pitch and yaw adjustment for a Ø1" off-axis parabolic (OAP) mirror mounted on a plate that positions the surface of the mirror at a 45° angle. The ports are SM1 threaded (1.035"-40) for compatibility with our SM1 Lens Tubes and each face has four Ø6 mm smooth bore holes for compatibility with the ER rods for our 30 mm Cage System. The top and bottom of the mount also offer 1/4"-20 (M6) mounting holes for compatibility with Ø1/2" and Ø1" Posts.
The rear-loading, removable mounting plate features our ball and V-groove design that allows it to be precisely kinematically positioned on the body of the mount. The rear-loading design ensures that the optic remains accessible even after the mount is fitted with cage rods or lens tubes.
For more information on KCB1P(/M) Mount, see the full web presentation.
Our Mounting Adapters for Ø2" Off-Axis Parabolic Mirrors provide mounting alternatives to our smooth bore kinematic mirror mounts. Each contains three #8 counterbores that are positioned to align with the 8-32 tapped holes on our Ø2" OAP Mirrors. Please note that these adapters will block the through holes on OAP Mirrors with holes parallel to the collimated beam. Our smooth bore mounting adapters can be used to mount these parts.
The SM2MP OAP Mirror Adapter is externally SM2 threaded (2.035"-40), which allows a Ø2" OAP mirror to be directly mounted to an internally SM2-threaded component. The adapter is designed to allow easy adaptability to a 60 mm cage system as well as SM2-threaded mirror, translation, and rotation mounts. The included SM2RR retaining ring secures the adapter in place when it is threaded into a mount. An SPW604 and SPW801 Spanner Wrench can be used to thread the retaining ring and adapter, respectively. Three low profile 8-32 cap screws and the required 5/64" hex key are provided with each adapter.
The unthreaded MP508P1 OAP Mirror Adapter is sized to fit inside a Ø3" mirror mount, such as the KS3 Mirror Mount shown above. Three standard 8-32 cap screws and the required 9/64" hex key are provided with each adapter.
The MP508P2(/M) OAP Mirror Adapter contains four 8-32 (M4) taps, for post mounting, that orient the OAP mirror at right angles. The distance from the center of the optic to the edge of the mount in the MP508P2 is 1.5" (38.1 mm), allowing for standardized optical axis heights when used with a fixed height post, such as our Ø1" Posts. Please note that the MP508P2(/M) is not compatible with Ø3" mirror mounts, and is instead designed for post mounting. Three standard 8-32 cap screws and the required 9/64" hex key are provided with each adapter.
The SM2MP3 Mounting Adapter for Ø3" Off-Axis Parabolic Mirrors offers a mounting alternative to our smooth bore kinematic mirror mounts. External SM2 threading (2.035"-40) provides a mechanically stable option for mounting Ø3" OAP mirrors into an internally SM2-threaded component. Two holes spaced 1.5" apart on the back can be used to secure the adapter with an SPW801 adjustable spanner wrench. The SM2MP3 adapter also contains four 8-32 taps, for post mounting, that orient the OAP mirror at right angles. Thorlabs offers a selection of screw thread adapters, including the AP8E4M 8-32 to M4 thread adapter, which can be used to mount the SM2MP3 adapter onto M4-threaded posts.
This adapter contains three 8-32 captive screws that are positioned to align with the 8-32 tapped holes on our Ø3" OAP mirrors. Captive screws can be secured with a 5/64" (2 mm) hex key (not included). The SM2MP3 adapter also features a radial alignment slot for use with the included dowel pin to assist when mounting to a mirror. A Ø0.16" (Ø4 mm) through hole at the center of the SM2MP3 adapter provides passage for a through beam parallel to the collimated beam. The back side features an internal SM1-threaded (1.035"-40) bore for mounting externally SM1-threaded alignment tools, such as the SM1A7 alignment disk pictured above to the far right.