Projects | Ege Küçükkömürcü

Compressed All-Optical Photoacoustic Imaging

Fri, 03 Jul 2026 00:00:00 +0000

The question

Photoacoustic imaging has a wonderfully inconvenient premise, send light into tissue, let optical absorption generate ultrasound, detect the sound, and reconstruct where the absorption happened. In principle, elegant. In practice, tissue scatters light, detectors have finite bandwidth, lasers have finite repetition rates, and biology refuses to freeze politely while we measure it.

My PhD asks a simple but annoying question:

Can we recover dynamic biological activity with fewer measurements, using an all-optical photoacoustic system, without throwing away the physics that makes the reconstruction meaningful?

The long-term motivation is neuronal activity imaging. The dream is to observe activity deep inside tissue using optical contrast and acoustic propagation, while avoiding the usual trap of building a beautiful imaging system that is too slow, too dense, or too idealized to survive contact with the experiment.

The approach

I work on compressed all-optical photoacoustic imaging. The system combines compressed optical ultrasound detection, and model-based reconstruction.

The main ingredients are:

Planar optical ultrasound detection
The detector is a transparent optical ultrasound sensor, such as a Fabry–Pérot cavity. This geometry is attractive because it can provide broadband ultrasound detection while leaving optical access to the sample.
Compressed detection with a DMD
Instead of scanning every point one by one, the detection can be patterned. This opens the door to compressed acquisition, where each laser pulse carries more global information than a single local measurement.
Inverse problems and sparsity
The measurements are incomplete by design. The reconstruction therefore has to use prior information: sparsity, positivity, temporal structure, and calcium-like dynamics.
Fast forward models
A reconstruction algorithm is only as useful as the model it believes in. I develop shift-invariant planar forward models for photoacoustic propagation, designed to be much faster than brute-force wave simulation while remaining physically meaningful.
Dynamic reconstruction
The biological target is not a statue. I study how to reconstruct time-varying activity when the acquisition process is constrained by laser repetition rate, measurement budget, and the general tragedy of finite time.

What came out of it

This is my main PhD project and it is ongoing.

So far, the work has focused on building and validating the computational core:

fast convolution-based photoacoustic forward and adjoint operators,
iterative reconstruction methods for planar detection,
compressed measurement strategies,
DMD-based compressed detection,
dynamic reconstruction models for calcium-like signals,
and experimental alignment/testing toward an all-optical acquisition path.

The main lesson is that reconstruction is not just an algorithmic decoration added after the experiment. It is part of the instrument. The physics, the sampling pattern, the detector geometry, and the reconstruction model all negotiate with each other. Usually rudely.

Why it mattered

This project is the center of my current research identity. It sits exactly at the intersection I care about: optics, acoustics, computational imaging, and inverse problems.

The broader goal is not just to make prettier photoacoustic images. It is to ask what can be measured when the acquisition is deliberately compressed, when the object changes in time, and when the reconstruction model is forced to admit that reality has constraints.

Status

Ongoing PhD project at Institut Fresnel, supervised by Thomas Chaigne and Marc Allain.

Part of the model-based reconstruction work is described in:

Ege Küçükkömürcü, Simon Labouesse, Marc Allain, and Thomas Chaigne. arXiv, 2026.

Visual Microphone

Thu, 02 Jul 2026 00:00:00 +0000

This was my final-year project at the Middle East Technical University Physics Department, and it was probably the first time my interests in optics, acoustics, and signal processing fully collided in a useful way.

The question sounded slightly ridiculous, which is usually a good sign:

Can we recover sound without using a normal microphone?

Instead of detecting pressure directly, we looked for sound in light. More specifically, we investigated whether acoustic vibrations could be recovered from changes in the speckle pattern produced by a multimode optical fiber.

At the time, I was fascinated by the idea that a messy optical pattern could contain hidden information about the environment. A speckle image looks random, but it is not meaningless. It is a fragile interference pattern, and fragility is often just sensitivity wearing dramatic clothing.

The idea

A multimode fiber supports many optical modes. These modes interfere at the output and create a speckle pattern. If the fiber is disturbed by sound or vibration, the optical path lengths of the modes change slightly. This changes the speckle pattern.

So the logic was:

sound perturbs the fiber,
the fiber perturbs the optical speckle,
the camera records the speckle fluctuations,
signal processing tries to recover the original sound.

In less polite terms: we asked whether a chaotic-looking optical blob could be bullied into becoming a microphone.

What we built

The setup used a 1550 nm laser, a multimode optical fiber, and a camera to record temporal changes in the speckle pattern. We played sound near the system and extracted signals from the recorded optical fluctuations.

The project involved:

optical alignment,
recording speckle patterns,
extracting temporal intensity variations,
filtering and signal processing,
comparing the recovered signal with the sound played through speakers.

We even tested it with actual music, including the Inspector Gadget theme, because apparently scientific seriousness has limits.

What came out of it

The main result was that sound could indeed be reconstructed from optical speckle fluctuations.

The reconstruction was not magically clean from the beginning. It required filtering and processing, and the signal was sensitive to the experimental conditions. But that was also the point: the speckle pattern was carrying acoustic information, even if it was doing so in the most unnecessarily dramatic way possible.

Listen

Original

Reconstructed

This project became important for me because it showed that optical systems can act as indirect acoustic sensors. That idea never really left me.

Why it mattered for me

Looking back, this project was one of the roots of my current research direction.

My PhD now deals with all-optical photoacoustic imaging, where ultrasound is detected optically rather than with a conventional piezoelectric detector. The physics and hardware are different, but the taste is similar:

use light to listen to sound.

The Visual Microphone project gave me an early intuition for optical acoustic sensing, speckle-based measurement, and the fact that the useful signal is often hidden inside something that initially looks like noise.

Acknowledgements

This project was carried out during my undergraduate studies at METU. I am grateful to Berk N. Gün for his contribution to the project and to Prof. Emre Yüce for his guidance.

Acoustic Levitation

Wed, 01 Jul 2026 00:00:00 +0000

The question

Can sound hold an object in the air?

Acoustic levitation is one of those experiments that looks like magic until you remember that pressure fields exist and are rude enough to push matter around. A strong ultrasonic standing wave can create stable pressure nodes and antinodes, allowing small objects to be trapped without mechanical contact.

The question was simple:

Can we create a stable ultrasonic field strong enough to levitate small particles, and what does that teach us about acoustic radiation forces?

The approach

The project was an experimental exploration of ultrasonic standing waves and acoustic radiation force.

The general idea was:

generate an ultrasonic field,
create a standing-wave configuration using a source and reflector or paired transducers,
tune the geometry and alignment,
place small lightweight objects in the field,
observe whether they become trapped near stable pressure nodes.

The setup is conceptually simple, which is exactly why it is dangerous. Simple acoustic experiments often hide all their difficulty in alignment, boundary conditions, transducer behavior, and the tiny humiliations of real hardware.

What came out of it

The project demonstrated and explored the physical basis of acoustic levitation: sound fields can exert steady forces on small objects.

The important part was not only making something float. It was developing intuition for how acoustic fields create spatial force landscapes, and how sensitive those landscapes can be to geometry, frequency, object size, and alignment.

In other words, the floating object is the cute part. The wave physics is the actual part.

Why it mattered

This project gave me hands-on intuition for acoustic fields, pressure nodes, radiation forces, and experimental wave systems.

It also connects to a broader theme in my work: waves are not just signals that travel from one place to another. They can measure, push, trap, perturb, and reveal. Sometimes they even levitate things, because apparently being invisible was not enough.

Status

Exploratory experimental project.

I keep it here as part of my acoustics background and as a reminder that even “simple” wave experiments are only simple on the blackboard.

Optical Detection of Sound Absorption

Tue, 30 Jun 2026 00:00:00 +0000

The question

Can an acoustic interaction be detected optically?

This project explored a recurring idea in my work: sound does not always have to be measured directly. Sometimes it can be detected through what it does to another physical system — especially an optical one.

The specific motivation was to think about sound absorption and acoustic interaction through optical signatures. If sound is absorbed, scattered, or otherwise modified by a material or medium, can that process be probed using light?

It is the kind of idea that sounds suspiciously indirect, which is usually where the interesting measurement problems begin.

The approach

The project considered optical readout strategies for acoustic phenomena.

The broad idea was:

generate or study an acoustic interaction,
observe how that interaction modifies the system,
use an optical measurement to detect or visualize the effect,
interpret the optical signal as an indirect probe of sound absorption or acoustic coupling.

Depending on the configuration, the optical signature may come from motion, intensity modulation, refractive-index changes, surface displacement, thermal effects, or other secondary consequences of the acoustic field.

The key point is that the optical measurement does not replace the acoustic physics. It gives another way of accessing it.

What came out of it

This was an exploratory direction rather than a finished standalone research program.

Its value was conceptual: it helped connect acoustic absorption, optical sensing, and indirect measurement. It sits on the same intellectual line as the visual microphone project and my current work in all-optical photoacoustic imaging.

All three ask related questions:

Can sound be detected optically?
Can an acoustic process leave a useful optical trace?
Can we reconstruct the physical cause from an indirect measurement?

The answer is often “yes, but please suffer first.”

Why it mattered

This project helped sharpen my interest in opto-acoustic measurement systems.

In my current PhD, photoacoustic signals are generated by optical absorption and detected through optical ultrasound sensors. This project belongs to the same family of ideas: acoustic information can be accessed through optical means, provided the model is honest about what is actually being measured.

Status

Exploratory/student project.

I keep it here because it helped shape my broader taste for optical sensing of acoustic phenomena.

Shear Wave Imaging Simulation

Mon, 29 Jun 2026 00:00:00 +0000

Question

How do shear waves propagate through tissue-like media, and what information can be reconstructed from simulated measurements?

Approach

The project uses simulation to study shear-wave propagation, imaging geometry, and stiffness reconstruction workflows.

Result / Status

This is a simulation-based study connected to my broader work with wave-based measurement and inverse problems.

Links

Links will be added when public material is available.

Projects | Ege Küçükkömürcü

Compressed All-Optical Photoacoustic Imaging

The question

The approach

What came out of it

Why it mattered

Status

Related preprint

Visual Microphone

The idea

What we built

What came out of it

Listen

Why it mattered for me

Acknowledgements

Acoustic Levitation

The question

The approach

What came out of it

Why it mattered

Status

Optical Detection of Sound Absorption

The question

The approach

What came out of it

Why it mattered

Status

Shear Wave Imaging Simulation

Question

Approach

Result / Status

Links