PIONEAR — A photonic microphone with better-than-human-ear sound quality
Popular-science summary
Microphones are now essential components of phones, computers, voice-controlled devices, teleconferencing systems, and many industrial applications. Despite enormous technological progress, today’s miniature microphones are still unable to simultaneously detect the quietest sounds audible to humans, very loud acoustic signals, and the full range of audible frequencies. The aim of the PIONEAR project is to create a prototype of a miniature photonic microphone with performance exceeding the capabilities of the human ear.
The new solution is based on a method developed within the project called chromometric sensing, in which sound is detected using light. An acoustic wave moves a membrane that simultaneously forms part of the laser resonator. The displacement of the membrane changes the length of the resonator and, consequently, the frequency of the emitted light. Instead of measuring very small changes in an electrical signal, as in conventional microphones, the system therefore measures very precisely the change in laser frequency. This approach has the potential to provide very high sensitivity and dynamic range while maintaining low power consumption.
The project combines photonics, semiconductor laser technology, micromechanics, photonic integrated circuits, and digital signal processing. Specially designed VCSELs, a miniature acoustic chamber with a membrane, an optical readout system, and a technology for integrating all these components into a compact device will be developed.
Project objective
The main objective of the PIONEAR project is to develop and experimentally demonstrate a new chromometric sensing method and to use it to build a prototype miniature microphone with very high sensitivity and dynamic range. The target microphone is expected to achieve self-noise not exceeding 0 dB(A) SPL, detect signals up to at least 130 dB(A) SPL, and operate over a 20 kHz bandwidth, thereby covering a range exceeding the capabilities of human hearing.
The project includes the development of specially designed electrically pumped VCSELs optimized for chromometric sensing, fabrication of a micromechanical membrane and acoustic chamber, development of micro-transfer printing technology for component integration, and development of a photonic readout system and digital signal processing methods that convert changes in optical frequency into a digital audio signal.
Project partners
The PIONEAR consortium consists of: Lumiary AB, Sweden – project coordinator, OST – Ostschweizer Fachhochschule, Switzerland – Associated Partner, VIGO Photonics S.A., Poland, Łukasiewicz Research Network – Institute of Microelectronics and Photonics, Poland, University College Cork – Tyndall National Institute, Ireland, Lodz University of Technology, Poland, accelopment Schweiz AG, Switzerland – Associated Partner.
The Swiss partners participate in the project as Associated Partners, with their participation funded by the Swiss State Secretariat for Education, Research and Innovation (SERI).
Role of Lodz University of Technology in the project
Lodz University of Technology is primarily responsible for the numerical design and characterization of the special VCSELs that constitute a key component of the photonic microphone. The TUL team performs advanced multiphysics simulations to analyse the influence of the number of quantum wells, the position and thickness of the oxide aperture, and the design of the DBR mirrors on wavelength tunability, emitted optical power, and other laser parameters. The calculations are performed using the PLaSK software developed at TUL, which accounts for the interaction between electrical, thermal, optical, and recombination phenomena.
TUL leads Task 2.1, “VCSEL design and characterisation of lasers”. The first generation of the VCSEL structure is designed on the basis of TUL simulations and subsequently optimized using feedback from epitaxial growth and processing carried out by VIGO Photonics and Łukasiewicz-IMiF, as well as experimental laser characterization performed at TUL. The structures designed by TUL then form the basis for the epitaxial growth of 940 nm VCSELs at VIGO.
Lodz University of Technology also participates in the development of VCSEL technology suitable for integration by micro-transfer printing. Together with VIGO and Łukasiewicz-IMiF, this work is expected to lead to new low-power laser sources that may be useful not only for chromometric sensing, but also for photonic integrated circuits and optical interferometry.
Expected impact of the project
The direct outcome of the project is expected to be a new generation of miniature microphones capable of recording both extremely quiet and very loud sounds while maintaining high signal quality. Potential applications include consumer electronics, professional audio systems, hearing aids, teleconferencing, and voice-controlled devices. Arrays of highly sensitive microphones may enable selective listening in a chosen direction, improving speech recognition in noisy environments.
The technology may also be important for robotics and autonomous transportation. Highly sensitive microphone arrays could use ultrasound for echolocation and navigation, complementing information obtained from LiDAR and radar systems. Combining different sensing modalities could improve the safety of vehicles and robots, particularly in situations where optical sensors are impaired, for example by fog.
The significance of the project extends beyond microphone technology. The same chromometric sensing principle may be applied to pressure and ultrasonic sensors, accelerometers and gyroscopes, biochemical sensors, as well as gas and aerosol detectors. The concept developed within PIONEAR may therefore provide a new platform for highly sensitive and energy-efficient optical sensors.
From a scientific perspective, the project aims to validate a new measurement approach in which information about the measured quantity is encoded in the laser frequency. This is expected to enable very high resolution at low optical power while reducing the need for power-hungry, high-resolution analogue-to-digital converters. From an economic perspective, the project may contribute to the development of new products in consumer electronics, audio, sensing, telecommunications, and photonics, and provide a basis for further commercialisation of the technology by European companies.
Project funding
The PIONEAR project, “A photonic microphone with better-than-human-ear sound quality”, is implemented under the Horizon Europe programme, EIC Pathfinder Open 2023 call, HORIZON-EIC-2023-PATHFINDEROPEN-01. The planned project duration is 48 months.
According to the budget presented in the proposal:
total value of the project activities, including funding for the Swiss partners: EUR 3 648 620,
total eligible costs of the beneficiaries funded directly under Horizon Europe: EUR 2 482 745,
budget allocated to Lodz University of Technology: EUR 376 750, funded at 100% from EU funds.