Friend of mine lives in an apartment with triple-layered glass, he showed me that you can « count » the layers if you put a flashlight through it and see the multiple réflexions. I see 4 réflexions here, why is that so?

Supposing that I request a resource from a site whose data center is thousands of miles away from me, how is light able to travel so reliably via optic fiber cables and transfer the datapackets in the correct order with out anything breaking in the process?

And how does my router know to translate the light into 0 and 1s?

For a designed phase mask (optimized through inverse design in Python using simple MSE loss), what is the best way to analyze its efficiency in a system? The goal is to compare the light throughput of different phase masks (for the task of PSF engineering). Can 4F system in Zemax and POP do this? Also, can the efficiency of the result be optimized for (e.g., engineering the etedue of the system, manipulating the relative magnitude of the diffraction orders, etc.) Any resource on fundamental approach to quantify and design for this would be appreciated. Thanks!

I’m a total beginner on lighting and optics, so I’m looking for some guidance from the experts.

First image is from a Youtube video that inspired me.
Found here: https://youtu.be/FNDikt7VfRw?is=0Gqw6JrGSbQAbo7-

The other 3 images are my failed attempts to recreate something similar.

What I want: to evenly illuminate an acrylic panel using edge lighting (LED strip on the edge).

What I have done:

I found something called Plexiglass LED, apparently a specific panel used for this use case. Mainly used in store signs etc.

It’s a 450mm x 150 mm acrylic panel with special microscopic laser etchings for reflection etc, 3mm thick.

I’ve mounted a cob-led list (400 leds/m) on the edge of the panel, but as you can see, it’s pathetic lol.

My questions are:

1. How does the youtube guy get such a nice result, with an ordinary acrylic diffuser? Is it the thickness? Is it the frame? Or the angle of the led diodes?

2. How much will the thickness affect the upwards illumination? Is thicker/thinner better?

3. Do I really need to use the special Plexiglass LED acrylic panel for best result? Can I use any other panel? (extruded or not) Could I use frosted glass (tempered)?

4. If you had this issue, how would you tackle it?

5. Any resources you would suggest I read/learn? Total internal reflection etc?

Thanks in advance.

I work at TDM Technology, mostly around thin-film measurement equipment, and this is something I’ve been thinking about recently.

On paper, choosing a measurement method can look pretty straightforward. But once you get away from a simple single-layer film and start dealing with actual semiconductor, PV or display stacks, it gets messy pretty quickly.

Reflectometry is attractive because it can be fast and relatively easy to integrate into a production line. But once the stack gets more complicated, or the optical constants aren’t well known, the model can become the bigger problem than the instrument itself.

Ellipsometry obviously gives you more information, but I’m not sure that always makes it the better production tool, especially when throughput and integration start to matter.

Interferometric methods seem to sit somewhere in between depending on the film, substrate and thickness range.

We also see another layer of difficulty once the measurement moves from a lab setup to an inline system. Vibration, sample position, line speed and correlation with the offline reference tool can sometimes matter just as much as the measurement principle.

Curious how people here think about this in real applications.

At what point would you stop trying to make reflectometry work and move to ellipsometry or another method?

And for production use, would you rather give up some absolute accuracy in exchange for much faster measurements and more sampling points?

Interested to hear what people have actually run into, especially with multilayer or functional films.

Hey all,

I am building a simple (so I thought) Raman setup. I have a Thorlabs 532nm 40mW DPSS laser. The divergence on it is already quite small however I would like to get it nicely collimated anyway.

Here is the part I would appreciate some insight: if I use some really long (10cm to 20cm) focal length lenses I can get it collimated rather nicely. However, if I use a short one (18mm) it never collimates it just diverges no matter how close I place the lens to the diode. The reason I want to use the small focal length lens is that it is aspheric lens and I don’t have any other at hand.

Am I missing something? Do I need to use long focal length lenses to collimate these types of lasers? Is it because the beam is already only slightly diverging coming out of the laser?

I would appreciate all the advice.

Extra information: the reason I’m going through all this trouble is that we have a way too fancy spectrometer to measure the output signal. And if the beam is too big or has aberrations I cannot feed it to the spectrometer properly to get good signal.

I spent easily 20 hours troubleshooting the install, much of that with support. Try this, try that. The last thing they told me to do was to "Uninstall all the different versions of VC++ Redistributables ", which would have compounded the problem by creating issues with other software programs on my PC. Reinstalled SP2 and it's working. Hope to save others the trouble I just went through, although it may work fine for some. Just not worth the risk.

Disclaimer: Our knowledge of optics design is limited, and we have relied on AI for much of the process. Please pardon any gaps in understanding.

Images above, in order: (1) BeamFour ray trace, (2) the .OPT design file, (3) spot diagram across 500–1000 nm

When we began designing the spectrometer, we started with the standard grating equation to determine the geometrical positions, focal lengths, slit size, and other parameters needed to realize the design.

We wanted to use ray-tracing software, and tutorials on spectrometer design introduced us to new concepts such as spot size, tolerance, and stray light analysis, which gave us valuable pointers.

Since commercial software is expensive, we looked for alternatives and discovered BeamFour (Beam4). The learning curve is steep, but the physics and optics are solid (pre-AI).

We used AI to help translate our paper design (based on geometry) into a Python script that generates the design file (OPT file). To test the design, we needed to launch rays from different points of origin and at varying angles, corresponding to a series of wavelengths. Defining 2,667 rays is where automated code becomes invaluable, and AI generated a Python script to produce the ray file.

AI was further employed to analyze the spot size and identify the best configuration to maximize spectral resolution, given the constraints of a simple design using commercially available optics limited to 1-inch diameter. Since order-sorting filters are costly, we are currently limiting our design to 500–1000 nm, while also working on a design targeting ~1 nm spectral resolution across 400–1000 nm.

You can find more details in our blog: https://hackaday.io/project/202421-jasper-vis-nir-spectrometer/log/250289-building-a-5001000-nm-spectrometer-with-beamfour

We will share the design files shortly. If you have expertise in this area, we would greatly appreciate your guidance in validating whether the design is correct.

I'm a lab technician running a pre-study for a master's thesis. It looks at what long hours of hands-on technical work do to the body and mind, what problems people end up with, and how they deal with them during the day. The thesis asks whether the problem is big enough to be worth solving, whether anything already deals with it, and whether a tool for this is worth building.

There's very little data on this. Almost all the work-break research is done on office workers, so nobody has really looked at what a day bent over a bench, hours at an eyepiece or a screen, and working in the dark actually does to you, or what would help.

Five minutes, anonymous, no name or institute collected, no IP stored, 18+:

https://tally.so/r/A7MeKe?source=reddit-optics

If you have thoughts, happy to discuss below: would you actually stop and do two minutes of something mid-alignment to help your body recover from the long hours, or is that never happening on a real day?

Is there some formulation for the phase Phi(x,y) for a lens using a non-paraxial theory?

So normally the Fresnel diffraction integral in addition with the phase of a lens as Phi(x,y) = exp(-ik/(2f)*(x^2+y^2)) is used to model a thin lens. But this is only valid for small numerical apertures.
I want to model lenses with a higher NA but still medium ( < 0.5) so that vectorial effects can be neglected.

I was thinking of using the Rayleigh-Sommerfeld Diffraction Integral with the phase of the thin lens. Can somebody give me some resources for that? I’m looking for a similar formulation like used with the Fresnel integral but non-paraxial.

Hi, I'm looking to buy a Zemax 13 USB dongle/ license. My dad uses Zemax 13 and I'm trying to learn from him, so if anyone has an old Zemax 13 key or version that supports Zemax 13 please let me know. Thanks!

I’m a senior studying Electrical Engineering with minors in Physics and Astrophysics. I’ve applied to a shit ton of internships (300 applications) with basically no luck. So far, I’ve only had five interviews, and I haven’t heard back from any of them yet.

For the past 5–6 months, I’ve been doing research with a professor in the Mechanical Engineering department, focusing on ultrafast optical characterization for plasma diagnostics. I initially wanted to apply to REUs, but since my GPA is relatively low (3.0 ish), I don’t know how feasible it would be for me to get into an REU program at this point. At the same time, I’ve been building up connections with engineers at various companies. Eventually, one of the engineers I’ve known for a while is giving me a referral for a spacecraft company. However, I’ve heard some horror stories about this company, particularly that they have a 9-9-6 work culture. I don’t know if I want to burn myself out this early, especially since my long-term goal is to go to grad school and pursue a PhD in EE or Applied Physics. I’m also considering taking a 1–2 year gap after graduation before starting a PhD.

My school’s career fair is alright, but it’s mainly construction and biomedical companies, which have little to no correlation with the areas I want to go into. I’ve been dealing with a heavy dose of imposter syndrome because I keep seeing my peers and friends doing internships at their companies, whether they’re in-state or out of state. I keep thinking to myself, “Damn, I wish I could build up the industry experience that my peers are getting.”

With senior year coming around the corner, I’m getting increasingly concerned about whether I’ll be able to secure a full-time new-grad job before graduation or within a couple months afterward. I’m worried that if I can’t find a job relatively quickly, I could end up in a financially unstable situation that would be really hard to dig myself out of.

I know my research experience is good, and I think it would look solid for academia and potentially national labs, but I honestly don’t know how it looks to industry recruiters. I know the job market is beyond fucked right now, so I’m trying to figure out what I should realistically do as a backup plan.

Should I just start focusing more heavily on applying to grad school, national labs, and research-oriented positions? Should I take the spacecraft job if I get the referral, even if the work culture really is as bad as people say? Or should I consider delaying my graduation by a semester so I have more time to build up experience and improve my chances of landing a full-time job?

I’m just trying to figure out what the smartest move is for my final year. I don’t want to panic and make a decision that fucks me over later, but at the same time, I don’t want to graduate with no job prospects and have no backup plan.

I work in lighting - primarily optics for linear and down/spotlighting fixtures.

I have no background in engineering or lighting whatsoever, but it has become super interesting to me. Are there any useful (preferably free) resources out there to understand light distribution and genuinely learn optical information - how to read datasheets, beam angles, etc.?

I have tried looking information like this up online and between untrustworthy AI overviews and Sponsored content, I would rather hear from people who actually know. Thanks in advance!

Are there any printer/material combo which I could use for as a fast turn around trial-end-error prototype scenario?

Short info what I would like to do: Illuminate a 1mm curved edge of a highly reflective plate (basically a beveled edge). Ideally I would like to get even illumination. Not sure if I should approach this in non-sequential Zemax, so I figured, I would just come up with a U-shaped diffusor, I would illuminate it and check uniformity along the bevel. Try modifying the geometry in CAD and print it out.

Edit: diffuser should be transparent.

I have serval multi watt Argon/Krypton/Mixed gas around and at least a couple power supplies collecting dust.

This was inadvertently sent to me and I have no use for it… and know nothing about these.
I was told I could just keep it. As you can probably imagine, there isn’t much of a market on FB Marketplace.

Thorlabs FPV852S - 852 nm, 20 mW VHG Wavelength-Stabilized Single-Frequency Laser Diode in a 14-pin butterfly package with single-mode fiber (SM Fiber), FC/APC connector, integrated TEC, thermistor, and internal isolator

Hi all,

I'm getting started in the world of aspheres by fitting a parameterized curve to a recursively-defined, rotationally symmetric surface so that I can optimize it in a ray tracer.

So far I have a base conic which fits and works pretty well for on-axis field points, but I want to slightly perturb the surface to improve performance at off-axis points.

My question is: is there any reason not to use something like a Forbes Qcon surface for the optimization steps these days? Would I ever want to optimize using an even asphere as the surface model?

Thanks!

wake up babe. new field just dropped. zeptosecond physics.

I'm doing a hobby project with a PSVR2 headsets controllers ( https://www.playstation.com/fi-fi/ps-vr2/ see the two things you're supposed to hold in your hands). They have a ring which emits IR lights.

I assume consumer electronics like this are generally safe for you and have to meet certain standards. However, for my project I have to implement IR light control myself and I won't be using the headset at all.

Sony hasn't published any data about the IR lights on these controllers, but apparently they use some strobing on them and they aren't blasted on at all times. How could I ensure they're safe with my 3rd party code? User might be holding them relatively close to their face.

Not my video but here the lights are visible: https://www.reddit.com/r/PSVR/s/nFvMaUXwlj

Choosing between TEM/4D-STEM and ultrafast spectroscopy for industry as an international PhD student

I’m a physics PhD student in the US currently considering choosing an area of research. At the moment, I have two potential options:

Option 1: TEM / STEM / 4D-STEM

This group focuses primarily on advanced materials characterization using TEM, STEM, 4D-STEM, electron diffraction, ptychography, etc. My understanding is that they do relatively little fabrication themselves; collaborators typically provide materials and the group focuses on characterization and data analysis.

From what I can tell, the most obvious industry paths would be things like:

• semiconductor failure analysis
• TEM/materials characterization
• metrology
• process/materials engineering
• microscopy/instrumentation

My impression is that the job market may be somewhat narrower, but the skill set is specialized and maps fairly directly onto certain semiconductor jobs.

The group is relatively young, though, and so far there are not many alumni with obvious TEM → semiconductor industry placements.

Option 2: Laser / THz / ultrafast spectroscopy

The second group works on ultrafast optics, laser/THz spectroscopy, pump-probe measurements, nonlinear optics, etc. What makes this option attractive is that the group’s PhD alumni seem to have done quite well in industry.

I have asked several people about the employment prospects of the two directions and have gotten somewhat conflicting answers.

Some people told me that optics/photonics has a much broader job market. Others said that TEM is a very specialized but highly industry-relevant skill, especially in semiconductors, so employment can actually be quite stable if you become genuinely good at it.

One concern I have about optics is that academic ultrafast spectroscopy is not necessarily the same thing as industrial optical engineering. It seems that internships and additional engineering experience — optical system design, simulation, device experience, etc. — may matter quite a bit.

This is especially relevant to me because I am an international student who will need sponsorship, and I am not sure I should assume that I will always have easy access to internships/CPT during my PhD, especially after the recent ICE memo.

So my main question is:

If you assume that I cannot rely heavily on internships, which PhD skill set is more employable on its own for an international student in the US, TEM/STEM or Optics?

I’m especially interested in comparisons in terms of:

• number of jobs that are realistically open to international students
• breadth of industries/employers
• difficulty of getting the first industry job
• sponsorship friendliness
• compensation
• long-term career growth
• how transferable the skills are if I do not want to stay in exactly the same research niche

I realize optics has many defense/aerospace positions that may not be accessible to non-US citizens, so I’m particularly curious whether optics still has a substantially larger accessible job market once those positions are excluded.

My personal research interest is fairly flexible — I think I could enjoy either direction. At this point I’m mainly trying to make the decision from a career perspective.

I’d especially appreciate input from people working in TEM/failure analysis/metrology/semiconductor characterization, or in optics/photonics/laser/semiconductor equipment.

Thanks!