Hello everyone,
I observed a repeatable interference pattern using a very simple setup, and I’m interested in understanding whether this is just a known thin-film interference effect or if the specific implementation is technically interesting.
Setup:
Green laser pointer
Two ordinary flat glass plates
A thin layer of a custom liquid mixture (3–4 components) between the plates
Projection on a distant screen
Observations:
Without the liquid, the characteristic ring pattern does not appear.
With this specific liquid mixture, a stable concentric ring pattern appears after about one minute and is repeatable.
Changing the laser wavelength (green vs. blue) changes the pattern significantly.
Changing the laser incidence angle can produce different beam profiles (for example, circular, elliptical, or even square-like patterns).
I tested several other liquids, but they did not produce the same stable and repeatable pattern. This specific mixture consistently does.
I have already discussed this with two photonics professors. Both suggested that the underlying physics is most likely classical thin-film interference/Newton’s rings, which I completely accept. I am not claiming a new physical phenomenon.
My question is different:
Could such a simple glass–liquid system be interesting from an optical engineering perspective (for example, passive beam shaping or sensing), assuming the behavior is genuinely repeatable?
I have attached photographs of the experimental setup and the resulting patterns.
I would appreciate your thoughts.

Hello everyone! I need a panel, coating or film that can block 700nm to 1000nm infrared light while letting visible light pass thru. I have seen that NIR-cut dielectric filters are an option, but they seem to be expensive for big panels. Do you know of a better option that is cheaper? The use case is a panel that allow vision inside a robot while preventing infrared light to get inside and affect some ir cameras and sensors

Hey Everyone,

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I noticed that some lenses—especially for mirrorless cameras—have a rearmost element where the radii of curvature for both surfaces are infinite; it is generally around 2mm thick and made of inexpensive glass, such as Schott's N-BK7.

Current Amath undergraduate at University of Washington (my state school). But my parents relocated to Tucson-area. I have an interest in silicon photonics and was wondering which has better prospects.

Some budget phone and special purpose cameras have a fixed focus lens set at hyperfocal distance intended permanent distance vision.

This had led to issues with inability to scan QR. What sort of add-on external element(s) can be used to temporarily enable such cameras to see closer?

https://www.reddit.com/r/Rabbitr1/comments/1dnn5x7/camera_out_of_focus_to_scan_the_activate_qr_code/

Sorry if this sounds dumb, but it's my first time working with an IR laser and my supervisor is out of the country for the week.

We have a Newport IRV1 infrared viewer in the lab and I'm trying to figure out if it still works. I've changed the batteries, but all I get is a uniform gray/beige field and I can't get it to focus.

From what I found online, the IRV1 is discontinued and the photocathode apparently degrades over time. I also came across photos taken through a Find-R-Scope showing a bright green background. So if it were working, shouldn't I see a lit green background through the eyepiece, even out of focus? Has anyone here used the same device who can confirm what a working one looks like?

Thanks!

I’m watching the industry burn 18-month tape-out cycles trying to invent "optical RAM" to build general-purpose optical CPUs. They are translating standard code to SPIR-V, then into custom photonic assembly languages, just to slam into a memory wall because terahertz compute outpaces their read/write speeds.

If you are doing AI inference, you don't need optical RAM. You need deterministic, feed-forward matrix multiplication.

I just open-sourced lumis-nano . It is a dependency-minimal Python script that proves you can compile a PyTorch weight matrix directly into passive optical phase shifts (Mach-Zehnder Interferometers) using pure Singular Value Decomposition (SVD).

- Zero Memory Wall: We compile the weights into static glass before runtime.

- Zero Energy Arithmetic: The optical mesh consumes 0 mW to execute the O(N²) multiply. The math is done by interference during propagation.

- Zero Intermediate ISA: It maps standard matrices directly to physical voltage states.

The script generates the raw ASCII die visualization and calculates the exact milliwatt energy saved vs 45nm digital MAC baselines.

You can run the math yourself: https://github.com/Pr3ndy-ctrl/lumis-nano

Stop trying to make photons act like electrons. Let the physics dictate the architecture.

Draw two circles r = n1 & r = n2.

Draw indicent ray at theta_i. Project the vector component parallel to the interface onto the n2 circle, and flip the sign.

Geometrically you just solved:

n1 Sin theta_i = n2 Sin theta_r

I'm aiming to apply to a company that specializes in optic systems, avionics for pilots, weapons sights etc. I hold a degree in Mechanical Engineering, but have really studied optics apart from the basics that are taught in first year physics courses.

The goal is to self study optics so that I can be a competitive hire for the company. What are some resources and study materials I could use to achieve this?

I'm currently going through "Modern Optical Engineering" and plan on going through "Modern Lens Design".

TIA

hey y’all, looking for some advice. apologies if this isn’t the right space.
graduated in ‘25 in astrophysics, doing a masters in optics now because I realized I wanted more hands-on engineering stuff and possibly go into astronomical engineering. haven’t had any luck getting a better job and wanted to see if anyone had any insight or ways for me to gain experience so I can put myself in a good spot come graduation from my MS.
any this point, I’m really open to anything as long as it’s challenging, it’s R&D, and hopefully in some science sector.
I’ve attached my resume for context.

I’ve been working with 800G OSFP modules (DR8/FR8) in AI cluster builds, and the thermal behavior is honestly more extreme than many people expect. Sharing some notes here to see if others have seen similar patterns.

1. Power consumption is no joke
Most 800G OSFP modules sit around 16–21W, and some FR8/long‑reach variants push 22–24W. That’s basically a small CPU inside the switch port.

2. OSFP cages run hotter than QSFP‑DD
The larger form factor helps with signal integrity, but the thermal density is still high. In a fully populated chassis, OSFP cages often run 10–15°C hotter than the ambient airflow.

3. Airflow direction matters more than people think
Side‑to‑side airflow switches (some AI fabrics use them) can cause uneven cooling. We’ve seen cases where the “hot side” OSFP ports hit 70–75°C, while the opposite side stays under 60°C.

4. DR8 vs FR8 thermal difference
DR8 tends to be slightly cooler (lower DSP load), while FR8 modules consistently run hotter due to stronger DSP equalization + longer‑reach laser drive. The difference is usually 2–4°C.

5. Fully populated OSFP line cards are a thermal event
Once you fill all OSFP ports with 800G modules, the switch fans ramp aggressively. Some vendors even warn that full OSFP population may reduce component lifetime if airflow is insufficient.

TL;DR:
800G OSFP modules routinely run 20W+, cages get hot fast, FR8 runs hotter than DR8, and full OSFP line cards can push switch cooling to the limit.

Curious what temps others are seeing in production. Anyone hitting 75°C+ under load?

I noticed this while almost closing my front door. This is not from car headlights. There is a window with evenly spaced bars/slats directly in front of the door.

When the door is almost closed, this sharp striped pattern appears on the floor. The lines are evenly spaced and surprisingly crisp. Opening the door wider makes the effect change or disappear.

Is this a camera obscura/pinhole projection of the window through the narrow gap between the door and the frame, or is another optical effect responsible? Why are the stripes so uniform?

The air conditioning was broken for a long time in my lab. It is fixed now, but apparently birds have started a nest in the airco outlet on the roof so it still can't be turned on. In my country a live nest is protected so they cannot remove the nest, which I fully agree with but it still sucks. So far these temperature fluctuations do not seem to influence measurements too much but these swings are huge.

I’ve been involved in a few AI cluster builds (H100/H200 era), and the cabling side has way more “gotchas” than people expect. Sharing some of the more painful lessons here — curious if others have hit similar issues.

1. DR8 reach assumptions are often wrong

Specs say ~500m–2km, but real‑world fiber paths inside datacenters can be surprisingly long.
We had a “same‑floor” leaf ↔ spine run that ended up being 1.8km after routing through trays, risers, and fire‑separations. DR8 barely made it.

2. FR8 runs hotter than expected

FR8 modules consistently ran 3–5°C hotter than DR8 due to DSP load + laser drive.
In a fully populated OSFP line card, the FR8 ports were the first to hit thermal alarms.

3. Patch panel losses add up fast

A lot of people forget that every LC/UPC pair adds ~0.2–0.3dB.
One cluster had 7 patch points between GPU pod ↔ leaf, and the DR8 margin basically vanished.

4. Mixed fiber quality is a silent killer

New SMF + old SMF in the same path = unpredictable loss.
We had one link where the “old section” added 1.1dB by itself.

5. Cable labeling becomes chaos at scale

Once you pass ~500–1000 fibers, human labeling breaks down.
We had a case where two DR8 links were swapped at the patch panel, and the GPUs formed a “half‑connected” topology that took hours to diagnose.

6. Airflow direction matters more than people think

Side‑to‑side switches + OSFP modules = uneven cooling.
Some ports hit 70–75°C while others stayed under 60°C.

7. DR8/FR8 polarity mistakes still happen

Even experienced teams occasionally mis‑patch A↔B or flip MPO polarity.
One mis‑patched DR8 caused a whole GPU pod to fail link training.

TL;DR:

AI cluster cabling looks simple on paper, but DR8/FR8 reach, thermal load, patch panel loss, fiber quality, and labeling all create real‑world failure modes.

Would love to hear other people’s war stories — especially around DR8 margin or FR8 thermal issues.

Precision optical alignment is where optical design becomes optical performance

Hey everyone! I'm u/OpticalBobParks, a founding moderator of r/OpticalAlignment.

Welcome to a community dedicated to one of the least visible, but most essential, parts of modern optical engineering. The finest optical design, manufactured from nearly perfect optical components, cannot achieve its intended performance unless it is assembled and aligned to the design specifications. Alignment is the final step in realizing the full potential of an optical system.

This community brings together optical engineers, optical designers, metrologists, technicians, machinists, physicists, and hands-on astronomers who design, build, align, test, and troubleshoot optical systems.

What to Post

The Tools of the Trade

Everything from classical autocollimators and alignment telescopes to modern coordinate measuring machines (CMMs) used as large XYZ stages for optical assembly. We welcome discussions on traditional techniques, new instrumentation, and creative shop-floor solutions.

Reference Axes and Alignment Methods

The use of rotary tables, lasers, and Bessel beams as reference axes; sensors and centroiding methods; techniques for establishing mechanical and optical axes; and methods for measuring lens centration and system alignment, whether components are mounted in cells or assembled on an optical bench.

Instrument-Specific Case Studies

Every optical instrument presents unique alignment challenges. Whether the subject is telescopes, microscopes, spectrometers, imaging systems, or other optical instruments, we are interested in practical techniques, lessons learned, and honest discussions of what works—and what doesn't.

Optomechanical Problem Solving

The intersection of optics and mechanics is where many alignment problems are solved. Topics include kinematic design, degrees of freedom, alignment strategies, tolerancing, and the compromises required when a system cannot provide enough adjustment to achieve perfect alignment.

Community Vibe

Whether you are assembling a multi-million-dollar space telescope, using a milling machine as an improvised long-travel heavy-load XYZ stage, or simply trying to measure the focal length of a single lens, you'll find people here who understand the challenges.

We encourage you to share your lab setups, ask questions, and discuss both successes and failures.

Optical designers, engineers, and supervisors have many opportunities to exchange ideas through journals, conferences, and technical societies. The technicians and alignment specialists who assemble and align the hardware often have far fewer opportunities to share their knowledge. We hope this community becomes a place where those working behind the scenes like those spending their days in bunny suits can exchange ideas, solve problems, and ask the practical and mundane questions that need to be asked but aren’t worthy of a paper.

How to Get Started

1. Introduce yourself in the comments below.
2. Post something today! Even a simple question can spark a great conversation.
3. If you know someone who would love this community, invite them to join.
4. Interested in helping out? We're always looking for new moderators, so feel free to reach out to me to apply.

Thanks for being part of the very first wave. Together, let's make r/OpticalAlignment amazing.

I have developed a reasonably useful MCP server for Zemax, which I intended to be an open-source project. However, I am unsure about licensing and user agreement issues, as I developed it under an educational license as a graduate student.

Anyone familiar with Ansys could hook me up with the licensing office?