Technology forum – laser – photonics

Tunable light-to-microwave conversion for integrated photonics

Semiconductor-based non-linear optoelectronic systems – thus devices that can convert light energy to electrical energy or vice versa – are drawing particular attention for their potential in photonic integrated circuits. Researchers at the Paul-Drude-Institut für Festkörperelektronik (PDI), Berlin, cooperated with colleagues at the Argentina-based Centro Atómico Bariloche and Instituto Balseiro (CAB-IB) in the development of an on-chip solid state time crystal, that could be used as a frequency converter.

Time instead of lattice periodicity

While conventional crystals consist of a periodic lattice structure, time crystals are composed of particles and quasiparticles like excitons, photons, and polaritons that vary periodically in time. Now for the first time, researchers have created a time crystal in microscale on a semiconductor chip that oscillates at GHz frequencies when excited with a continuous-wave near-infrared laser. The researchers also found that the oscillations could be fine-tuned by the laser’s optical power, with the possibility to stabilize the frequency by engineered 20-GHz mechanical vibrations of the semiconductor atomic lattice. In accordance with their theory, the researchers found that on further increasing the laser power the particles vibrated at exactly half the frequency of the mechanical vibrations.

Solid state quantum well

The sample, designed and fabricated at PDI, was created by stacking one-atom-thick layers of semiconductor materials under ultrahigh vacuum conditions, eventually forming a micron-sized quantum well with the ability to trap millions of quantum particles. It was then transferred to CAB-IB for testing.

Light-to-microwave frequency converter

According to the research team, this experiment shows promise for using time crystals in integrated and microwave photonics. “Due to the polariton-enhanced coupling between GHz phonons and near-infrared photons, the results have the potential for applications in (quantum) conversion between microwave and optical frequencies,” said Paulo Ventura Santos, a senior scientist at PDI.
Alejandro Fainstein, the senior researcher and professor who led the CAB-IB team, says: “Because the materials involved are semiconductors compatible with integrated photonic devices, and the frequencies displayed are relevant for both classical and quantum information technologies, we envision additional stages in which we will try to control these behaviors for applications, including photon-to-radiofrequency conversion at the quantum level.”

Original publication:
[Solid-state continuous time crystal in a polariton condensate with a built-in mechanical clock, I. Carraro-Haddad, D. L. Chafatinos, A. S. Kuznetsov, I. A. Papuccio-Fernandez, A. A. Reynoso, A. Bruchhausen, K. Biermann, P. V. Santos, G. Usaj, and A. Fainstein, Science, Vol 384, Issue 6, 2024, DOI: 10.1126/science.adn7087]

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