Great video! I recently got a shear-plate and it has been very useful for checking collimation in tight regions of my optical setup. I think a video highlighting clever usages of the cage system would be very useful. I have seen colleagues with some nice tricks, but haven't found many great examples online.
@SammerX Thanks for letting us know you like the video, and a big thank you for suggesting a video topic - we love to get recommendations! Would you be willing to share the tricks that impressed you? Or let us know what cage system examples you looked for online? This will help us kick off our brainstorming session :)
Another amazing video. I haven’t used a Shear-Plate in the lab, and I’m wondering what kinds of affects you would see if your beam was not parallel with respect to the optical table. I can imagine you could still cause an interference pattern at top of the Shear-Plate with a tilted beam which might cause confusion with determining the point of collimation.
@danieldahl It's great to hear the video got you thinking about different things that could affect the fringes you would see! You are correct that changing the angle between the incident beam and the shear plate will have an effect. Since the shear plate is wedged top-to-bottom, the effect depends on whether the input beam is misaligned side-to-side (yaw angle) or up-and-down (pitch angle). If the incident beam is not parallel to the table, then the beam is misaligned in pitch. Assuming the pitch angle is small and there are no other aberrations or misalignments, a collimated beam will still produce fringes that are parallel with the reference line on the ground glass diffuser. However, it is still necessary to keep the pitch angle small, since the angle of the two beams reflected from the shear plate changes as the pitch angle changes. As the pitch angle increases, the interference pattern will walk off of the ground glass diffuser. If the incident beam is misaligned in yaw, then a collimated beam will produce fringes that are tilted with respect to the reference line. The tilt angle increases as the yaw angle increases. In the case of yaw misalignment, the reference line on the diffuser would not correctly indicate the orientation of the fringes when the beam is collimated. The interference pattern will also walk off of the ground glass diffuser as the yaw angle increases. These are two of the reasons we used a rail in the demonstration.
Excellent video and well explained. Can this method be used with off-axis parabolic mirrors or do they introduce wavefront errors? Specifically can it be used to focus a beam expander/reducer that uses OAP mirrors instead of lenses.
@chromarti Yes, a shear-plate tester can be used to optimize the collimation of a beam provided by an OAP beam expander/reducer pair. While the wavefront error contributed by OAPs is not zero, it is low, and the beam quality OAPs provide can be high. For example, when the OAPs are properly aligned to the input beam, these mirrors should add negligible spherical, coma and distortion to the beam.
@rishabhsangal5155 Thanks, we're glad you found the video useful! Have you seen our OAP Video Insight ( th-cam.com/video/l8v8RyCi4HU/w-d-xo.html ), which shows an approach for using an OAP to collimate light diverging from a multimode fiber? The same general method applies to collimating diverging light from a beam focus or directly from a light source. Were there aspects you felt were missing in that video, or are there additional OAP approaches you would like to see?
@@thorlabs Ohh no, i am sorry. I have seen collimation video. What i wanted to ask is BEAM EXPANSION (2X, 3X...) USING ONLY OAPs. made a mistake in previous comment. Been using expanders with lenses for long time, out curiosity just want to learn with OAPs. Hope you can give some tips. and thank you for your response. : )
Do the tip and tilt of the shear plate need to be adjusted? If yes, how? In the video, it seems that was already taken care of by the mounting of the shear plate.
@user-zo2xy4iu8g There are no tip/tilt adjustments available on the shear-plate collimation tester. The housing holds the shear plate at a 45° fixed angle to the horizontal. In the demonstration, the laser and lens mounts were pre-aligned to ensure the light traveled parallel to the table and along the rail. We relied on the mounting configuration (post, post holder, and rail) to keep the device vertical to the table. If the input beam cannot travel parallel to the table, turning mirrors could be used to realign the input beam. Alternatively, the tester could be mounted to a KM200PM ( www.thorlabs.com/thorproduct.cfm?partnumber=KM200PM&YVI=9 ) to adjust the tip and tilt.
Great video! I recently got a shear-plate and it has been very useful for checking collimation in tight regions of my optical setup.
I think a video highlighting clever usages of the cage system would be very useful. I have seen colleagues with some nice tricks, but haven't found many great examples online.
@SammerX Thanks for letting us know you like the video, and a big thank you for suggesting a video topic - we love to get recommendations! Would you be willing to share the tricks that impressed you? Or let us know what cage system examples you looked for online? This will help us kick off our brainstorming session :)
Another amazing video. I haven’t used a Shear-Plate in the lab, and I’m wondering what kinds of affects you would see if your beam was not parallel with respect to the optical table. I can imagine you could still cause an interference pattern at top of the Shear-Plate with a tilted beam which might cause confusion with determining the point of collimation.
@danieldahl It's great to hear the video got you thinking about different things that could affect the fringes you would see! You are correct that changing the angle between the incident beam and the shear plate will have an effect. Since the shear plate is wedged top-to-bottom, the effect depends on whether the input beam is misaligned side-to-side (yaw angle) or up-and-down (pitch angle).
If the incident beam is not parallel to the table, then the beam is misaligned in pitch. Assuming the pitch angle is small and there are no other aberrations or misalignments, a collimated beam will still produce fringes that are parallel with the reference line on the ground glass diffuser. However, it is still necessary to keep the pitch angle small, since the angle of the two beams reflected from the shear plate changes as the pitch angle changes. As the pitch angle increases, the interference pattern will walk off of the ground glass diffuser.
If the incident beam is misaligned in yaw, then a collimated beam will produce fringes that are tilted with respect to the reference line. The tilt angle increases as the yaw angle increases. In the case of yaw misalignment, the reference line on the diffuser would not correctly indicate the orientation of the fringes when the beam is collimated. The interference pattern will also walk off of the ground glass diffuser as the yaw angle increases. These are two of the reasons we used a rail in the demonstration.
Excellent video and well explained. Can this method be used with off-axis parabolic mirrors or do they introduce wavefront errors? Specifically can it be used to focus a beam expander/reducer that uses OAP mirrors instead of lenses.
@chromarti Yes, a shear-plate tester can be used to optimize the collimation of a beam provided by an OAP beam expander/reducer pair. While the wavefront error contributed by OAPs is not zero, it is low, and the beam quality OAPs provide can be high. For example, when the OAPs are properly aligned to the input beam, these mirrors should add negligible spherical, coma and distortion to the beam.
Very informative video as always. Can you also give some tips for collimating a laser beam using only OAPs. Thank you.
@rishabhsangal5155 Thanks, we're glad you found the video useful! Have you seen our OAP Video Insight ( th-cam.com/video/l8v8RyCi4HU/w-d-xo.html ), which shows an approach for using an OAP to collimate light diverging from a multimode fiber? The same general method applies to collimating diverging light from a beam focus or directly from a light source.
Were there aspects you felt were missing in that video, or are there additional OAP approaches you would like to see?
@@thorlabs Ohh no, i am sorry. I have seen collimation video. What i wanted to ask is BEAM EXPANSION (2X, 3X...) USING ONLY OAPs. made a mistake in previous comment. Been using expanders with lenses for long time, out curiosity just want to learn with OAPs. Hope you can give some tips. and thank you for your response. : )
@rishabhsangal5155 Thanks for helping us better understand what you had in mind! Thanks also for the topic suggestion, we have added it to our list!
nice video！❤❤❤
Do the tip and tilt of the shear plate need to be adjusted? If yes, how? In the video, it seems that was already taken care of by the mounting of the shear plate.
@user-zo2xy4iu8g There are no tip/tilt adjustments available on the shear-plate collimation tester. The housing holds the shear plate at a 45° fixed angle to the horizontal. In the demonstration, the laser and lens mounts were pre-aligned to ensure the light traveled parallel to the table and along the rail. We relied on the mounting configuration (post, post holder, and rail) to keep the device vertical to the table.
If the input beam cannot travel parallel to the table, turning mirrors could be used to realign the input beam. Alternatively, the tester could be mounted to a KM200PM ( www.thorlabs.com/thorproduct.cfm?partnumber=KM200PM&YVI=9 ) to adjust the tip and tilt.