In this blog, the Physics Department at Durham University have shared how they use 3D printing for rapid prototyping and production in their “Rydberg Quantum Optics” lab work.

Scientific Abstract

The lack of intrinsic interactions between optical photons combined with the ability to control the propagation of photons using optics makes them ideal carriers of information. At the same time, the lack of interactions makes processing of the encoded information at the level of individual quanta difficult. In conventional nonlinear optics, nonlinearities become apparent only at very high intensities. The Rydberg Nonlinear Quantum Optics project focuses on the creation of strong optical nonlinearities and effective interactions at the level of individual photons by interfacing optical photons with ultracold Rydberg atoms [1-3] confined in magneto-optical (MOT) and optical dipole traps, which exhibit strong dipolar interactions over distances of many micrometers.

General Abstract

In our lab we work with Rydberg atoms; these atoms are highly energetic and can be thousands of times larger than normal atoms. The huge size of these excited atoms means they interact with one another. We can use this effect to generate one of the most unfathomable particles: single photons. As well as being able to witness and utilise the effects of one atom on another, our lab uses the latest techniques to control the fundamental properties of the atoms (for example, their opacity). This allows us not only to generate single photons, but to gain control over these photons, dictating their speed and direction in a way never previously realised.

3D Printing

Our group makes much use of 3D Printing for rapid prototyping and production. Here are a sample of our applications.

3D Printed Mount for Spectroscopic Cell

This item is of a nonstandard size. Without the ability to 3D print this mount we would have probably asked our in house workshop to construct a mount from aluminium; a heavier, costlier, bulkier, and altogether less useful option.

3D Printed Beam Profiler

It is routine to profile laser beams in our lab, which involves taking a series of images of the laser beam at different distances from the laser. This is time consuming and error prone. To save time, we have constructed this 3D printed laser beam profiler, including a 3D printed rack and pinion visible in the last two images. A Raspberry Pi controls the movement of the camera via a stepper motor attached to a 3D printed pinion and takes images automatically at specific distances using the camera. This produces accurate profiles in a fraction of the time it takes to perform this task by hand. It is also not susceptible to the errors of measurement that commonly occur when this is done by hand.

3D Printed Power Meter Head Holders

Our lab regularly measures the power of our lasers to ensure they are all functioning correctly. Unfortunately we have many lasers which all require accurate measurement. We have much fewer power meters than lasers, and it takes a few minutes to secure the power meter before a laser every time we want to take a measurement. Thus the measurement of 10 lasers can take twenty tedious minutes. 3D printed power meter head holders, tailored to the exact size of our power meter head, have recently been placed in all of the spots where we routinely measure laser power. Dropping the power meter head into these holders takes seconds and reduces a 20 minute job to around one minute. This enables us to concentrate on the physics that we do, rather than continually worrying about laser power.

3D Printed Beam Blocks

Troubleshooting in our lab generally involves a process of elimination involving all of our lasers. We will block one laser and observe the effect, then block another and observe until we have determined which one is causing an issue. As such, we regularly need to block and unblock beams, and it helps to have beam blocks in place and ready to go for this procedure. These 3D printed beam blocks print rapidly, and contain a magnet, whereby they can affix to our steel optical table. They are reliable, stable and most importantly, so cheap to produce that we can afford to place them all over the lab. As with most of our applications of 3D printing, there are naturally other ways of achieving the same aims. However, it is unlikely that we
would have ever pursued anything like this if it were not for the low cost and ease of 3D printing.

Knife Edging Cover

To measure the size of our laser beams, it is common to translate a knife edge across the beam and see how fast the laser beam is extinguished. For small beams (100 micron or less), this requires working with extremely sharp razor blades in a lab environment. As such, the blades must be protected to avoid injury. Here, we have 3D printed some really small knife edge covers. These allow us to use only one small part of the razor blade, which we have cut from a larger blade using a guillotine. This small blade is fixed into the knife edge cover with epoxy. The small hole in the casing opposite the blade is to mount the knife edge to other equipment for translation of the blade.

A 3D printed cover is perfectly adequate here, but would have been made by our workshop from aluminium in the absence of a 3D printing facility. As such we have made 10 of them for redundancy. They form an integral part of our experiment, as the size of our beams is crucial to the physics we are studying. Initial alignment of our experiment would be significantly more difficult without these tiny razor covers.

Heater Prototype

Here (image on right) we have a heater for a glass phial of atoms which is contained within the brass enclosure. This is an intricate part with tight tolerance, containing glassware filled with atoms. It also has ports / holes for electrodes which measure temperature, and for the heater itself. As such, both sides of the heater enclosure were 3D printed before fabrication from brass to ensure a snug fit. A good thing too; since the final version that was fabricated was prototype no.3 (image on left). Prototyping using the 3D printer helps us to avoid errors. The brass enclosure represents about 20 man hours of construction.

Cage Beam Blocks

These are not available from the manufacturer of the cage systems. It is easy to block a beam less elegantly with paper etc.. and to our mechanical engineering service would not consider these worth producing. They are, however, extremely practically useful.

Camera Enclosure

This CCD camera enclosure is much more compact and useful than the original that came with this CCD. It is being used to monitor the modes of a Stable Laser Systems optical cavity (the steel drum).

Cable Clips

These clips are quick to manufacture, and help keep the lab tidy.

Brewster Cell Mount

Here again we use the 3D printer to prototype a mount for a sensitive item. This mount is to be manufactured in Brass by our mechanical engineering workshop.

The CREATE Education Project would like to thank Michael Armstrong, Laboratory Technician Supervisor in the Department of Physics at Durham University for sharing this blog with us.

Group Web Page

https://www.jqc.org.uk/research/rydberg-nonlinear-quantum-optics/

Reference Sample

https://www.nature.com/articles/nphys4058
https://www.researchgate.net/publication/311855437_A_high_repetition_rate_experimental_
setup_for_quantum_non-linear_optics_with_cold_Rydberg_atoms

For more references contact Nicholas Spong (Nicholas.l.spong@durham.ac.uk)

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