Public defence in Photonics and Nanotechnology, M.Sc. Aigar Vaigu

The title of the thesis: Development and implementation of measurement principles from single-photon applications to telecom

Thesis defender: Aigar Vaigu
Opponent: Dr. Jan C. Petersen, Danish National Metrology Institute, Denmark
Custos: Prof. Erkki Ikonen, Aalto University School of Electrical Engineering

How do you reliably measure and calibrate light when dealing with just a few photons? This doctoral research tackles that question, introducing methods and devices needed to measure ultra-low light levels and ensure those measurements are accurate and trustworthy. 

The work presents two main innovations. First, it showcases a single-photon source based on tiny light sources - silicon-vacancy centres in nanodiamonds. By precisely controlling how often the source is excited by a laser, the brightness of this source can be adjusted predictably. In other words, the operator can decide how many photons are generated. This demonstration shows a clear way towards “light standard” at the few-photon level —crucial for testing and calibrating ultra-sensitive light detectors in quantum technologies, secure communications, and advanced scientific experiments. 

Second, the thesis describes several innovative transmission trap detectors. These detectors collect the light using specially arranged photodiodes. The advantage of these trap detectors is better insight into how the detector behaves and how much light is actually passing through. 

All of this is important because today’s cutting-edge technologies—such as quantum technologies and next-generation optical communication—depend on handling light at extremely low levels and doing it reliably. 

Keywords: radiometry, single photon source, trap detector

Thesis available for public display 10 days prior to the defence at Aaltodoc.