Align an Off-Axis Parabolic (OAP) Mirror to Collimate a Beam (Viewer Inspired)

Align an Off-Axis Parabolic (OAP) Mirror to Collimate a Beam (Viewer Inspired) | Thorlabs Insights

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Күн бұрын

Off-Axis parabolic (OAP) mirrors are often used to collimate divergent beams, but aligning these mirrors can be a frustrating experience. This is because there are multiple variables that must be controlled during the alignment process. This demonstration divides the procedure into discrete steps and includes helpful tips for successfully positioning the mirror and light source. In addition, the dependence of the correct alignment on the mirror's geometry is discussed, and the typical effects of different misalignment geometries on the beam shape are shown on a viewing screen.
In this demonstration, the divergent output of an optical fiber and an OAP mirror are aligned so that the incident light and the collimated reflected beam travel in a plane parallel to the surface of the optical table. Because of this, an important initial step in the procedure is to set both the height of the source and the center of the mirror mount's bore at the height of the desired collimated beam. Then, an iterative approach is used in which the mirror is rotated to bring the plane of reflection parallel to the plane of the table, and the fiber's end face is moved to the mirror's focal point.
00:00 - Introduction
01:00 - Alignment and the Parent Parabola
02:12 - Attach the Adapter to the Mirror
02:55 -Mount and Coarsely Align the Mirror
04:58 - Set Mirror and Source Heights to be Equal
05:39 - Initial Positioning of Mirror and Source
07:20 - Fine Positioning of Mirror and Source
10:37 - Beam Quality, Options, and Having Patience
Key Components used in this Demonstration Include:
- MPD149-F01-Off Axis Parabolic Mirror, Ø1", 90°, RFL = 4": www.thorlabs.com/newgrouppage...
- SM1MP SM1 Adapter for Ø1" Off-Axis Parabolic Mirror: www.thorlabs.com/newgrouppage...
- KC1-T Kinematic SM1-Threaded Mount: www.thorlabs.com/newgrouppage...
- R2 Post Collar: www.thorlabs.com/newgrouppage...
Other Components Include:
- M625F2 Fiber Coupled LED: www.thorlabs.com/newgrouppage...
- LEDD1B T-Cube LED Driver: www.thorlabs.com/newgrouppage...
- M15L01 SMA-SMA Fiber Patch Cable: www.thorlabs.com/newgrouppage...
- LMR1 Lens Mount: www.thorlabs.com/newgrouppage...
- SM1SMA SMA Fiber Adapter Plate: www.thorlabs.com/newgrouppage...
- EDU-VS2 Smaller Viewing Screen: www.thorlabs.com/newgrouppage...
- EDU-VS1 Larger Viewing Screen: www.thorlabs.com/newgrouppage...
- BHM3 Ruler: www.thorlabs.com/newgrouppage...
- SPW602 Spanner Wrench: www.thorlabs.com/newgrouppage...
- BM075 Magnetic Button Clamps: www.thorlabs.com/newgrouppage...
- HW-KIT2 1/4"-20 Cap Screw and Hardware Kit: www.thorlabs.com/newgrouppage...
For more photonics how-to videos, visit www.thorlabs.com/newgrouppage...

Пікірлер: 20

@blueberrydetective7323 2 жыл бұрын

I really appreciate all of these tutorial videos. They are very informative and help a lot with learning about components I am unfamiliar with. Happy Holidays!

@thorlabs 2 жыл бұрын

That makes us happy, thanks! Your username caught our attention - do you use photonics components to probe the mysteries of this superfood? We'd love to hear more, if you do! And, if there's a photonics component or lab practice you'd be interested in seeing in a video, we'd like to hear about that, too :)

@blueberrydetective7323 2 жыл бұрын

@@thorlabs No requests at the moment, just trying to expand my knowledge base. Thanks again!

@TushhsuT 2 жыл бұрын

Nice tutorial. Thank you! I believe I did such alignment once and it was a pain. Especially if one wants to refocus the beam, keeping nice gaussian shape in a focal spot.. As a suggestion - there are some parts which always need to be horizontal/vertical, being actually round and don't having any horizontal or vertical edge.. An example is just in the video. It would be much easier to align having a small reference face. For example - a part of long part of zylinder could be flattened (CNC, lathe/milling machine) during manufacture process, when one still exactly know where the axis is. It should not be big - 5x5 mm plane would be more than enough. Same for wedges, periscopes, etc. One could than simply take a screwdriver or hexkey, press it to this small reference plane with a finger and align element vertical/horizontal/aligned to holes on the table looking on some line (screwdriver) to orient. Would one want to be even more precise - some additional laser beam could be reflected from a piece of flat mirror attached to this surface and make a perfect horizontal alignment. By this, the probability of an accident during wedge or periscope alignment could be strongly reduced. IMHO

@thorlabs 2 жыл бұрын

Thank you very much for the compliment, we’re very happy you found the video useful. You’re absolutely right that including a reference plane can be very helpful when trying to align circularly symmetric optics. We did something similar on our aspheric fiber collimators that are pigtailed with PM fiber ( www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=13154 ) so the user knows the orientation of the fiber axis. We will pass along your suggestion to our product development teams to continue the practice and consider adding it to existing products.

@rachelanderson1232 11 күн бұрын

Great video! I assume these same techniques can be used to align spherical mirrors too?

@thorlabs Күн бұрын

@rachelanderson1232 We are glad you liked the video! While this video includes alignment techniques generally useful for spherical and off-axis parabolic mirrors, there would be challenges to using the complete demonstrated approach to align spherical mirrors. One challenge is that the focal region of spherical mirrors is directly in front of the mirror (i.e. these mirrors have obstructed focal regions). Since a spherical mirror’s collimated beam passes over its focal region, a fiber end face placed within the focal region would create a shadow in the collimated beam, which may not be desirable for the application. (This is the geometry of Newton telescopes.) If an off-axis approach is used with the spherical mirror, the collimated beam will be aberrated (primarily due to astigmatism, which is caused by the spherical mirror shape). Additional optics would likely be needed to improve the beam quality.

@rishabhsangal5155 Жыл бұрын

Hello, very helpful tutorial. I was also trying collimation/beam expansion with lenses(Achromats), i am using your SI254 to check the collimation and I am always getting curved fringes(aberrations) in shear. I was wondering is it my alignment fault or do we get better collimated beams with OAPs than lenses, any advise?

@thorlabs Жыл бұрын

Both OAPs and lenses can provide well-collimated and low-aberration beams, and the best option depends on the details of the setup. Without more information about your setup, it is difficult to know whether using OAPs would benefit your application. If you contact Thorlabs Tech Support ( techsupport@thorlabs.com ), we can discuss your setup with you and help you find a solution. One thing to note is that it is possible the aberrations are not due to your lens or the alignment. The aberrations might originate from one or more other locations in your setup, including the light source.

@raoufkutaish1294 10 ай бұрын

Could you please tell me what should I order from Thorlabs to have the same LED that you used for alignment? The number of the fiber-coupled LED and the LED mount.

@thorlabs 10 ай бұрын

@raoufkutajsh1294 The LED we used in the demonstration is the M625F2 and its driver is a LEDD1B. If you need a power supply, the KPS201 is compatible. Links to the LED, its driver, and other components used in the demonstration can be found in the description. This is a link to the KPS201 power supply: www.thorlabs.com/thorproduct.cfm?partnumber=KPS201&YVI=18 .

@lahuiss2040 6 ай бұрын

what is the source used ? it is ok to use a divergent lens with a USB PL201 laser ?

@thorlabs 5 ай бұрын

@lahuiss2040 The source used in this demonstration was a fiber-coupled LED emitting around 625 nm. For more information about this source, click the link to this source in the description. (The link is the first after the “Other Components Include“ header.) Since the beam from the PL201 is collimated, a lens could be used to focus/diverge the beam, and then an OAP could be used to re-collimate.

@moeswartz888 2 жыл бұрын

That's only half of the game. There is only a little chance that the fiber tip is perfectly placed into the focal plane of the oap. Ideally you want to focus the beam onto a small pixel detector for fine adjustment of the input w.r.t. the oap.

@thorlabs 2 жыл бұрын

You are absolutely right, it is sometimes necessary to make fine adjustments to the pointing angle and relative height of the fiber tip with respect to the mirror. For example, this becomes especially important when using an OAP to couple light from a collimated beam into a fiber, opposite the direction demonstrated in the video. For those who are curious, when the pointing angle and/or height of the input fiber tip is misaligned, the effect on the output beam would be similar to, but less severe than, that shown between 9:06-9:29, when the OAP was rotated in the SM1-threaded bore of the mount. We provided this demonstration thinking it would assist most users in the task of achieving an output beam whose collimation and beam path would be evaluated using a standard ruler with millimeter increments. If further precision is required for the application, it could be helpful to also place the fiber in a kinematic mount and tune both kinematic mounts' adjustors as required. Using a beam profiler or camera to check the circularity and direction of propagation would be a great way to confirm the beam shape and direction of propagation at the micrometer level. Please let us know if it would be helpful to show these additional steps to improve the precision of the collimated beam, use the OAP to couple light into a fiber, or anything else!

@selahthales 2 жыл бұрын

Nice video -- although I think the other way around is a tougher procedure. I really wished the optical conpanies could do a precision flat surface on the OAP near one edge -- with that, refocusing becomes trivial.

@thorlabs 2 жыл бұрын

@@selahthales Thank you very much for suggesting a feature addition that you think would make it easier to align OAPs! We'll pass along your recommendation to our development engineers.

@selahthales 2 жыл бұрын

this would help for sure. check the EO monolithic beam expander video

@thorlabs 2 жыл бұрын

@@selahthales Thanks for connecting us with this example, it definitely helps us better understand the functionality you're looking for.