Technology forum – laser – photonics

Lasers, 3-D imaging, PICs: developments for quantum technologies

The Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (FBH) will provide an insight into the institute’s current developments in the field of quantum technologies as part of the European Quantum Technology Conference (EQTC), which will take place in Hannover, Germany, from October 16 – 20, 2023. According to FBH, it has the complete value chain in-house: from chip design and processing to the production of microintegrated, particularly compact and robust modules and systems. It will be showcasing its extensive range of services at EQTC. Research and development work in the field of quantum technologies is carried out in particular by the four joint labs in which FBH cooperates with Humboldt-Universität zu Berlin. According to FBH, these joint research groups successfully bridge the gap between basic and application-oriented research.

Lasers for quantum sensor technology

Among other things, the Berlin research institute develops and supplies complex and robust laser modules for quantum sensors used on sounding rockets, on the ISS and on satellites. The modules deliver 500 mW in a single-mode fiber at > 20 % conversion efficiency (electrical to optical) and offer a narrow intrinsic linewidth < 1 kHz. According to FBH, they enable quantum sensing applications in fundamental physics, geo- and environmental physics, and timing and navigation. At their core are diode lasers in the wavelength range from 620 to 1180 nm. For all systems, especially for space projects, FBH performs extensive reliability and environmental tests.

FBH laser modules are also used to build compact quantum sensors and optical frequency references (OFR) for use in space. For example, an ultra-compact (volume < ½ liter) autonomous frequency reference based on the D2 transition in rubidium at 780 nm was demonstrated. It is expected to achieve a short-term stability of 1.7 x 10-12 at 1 second. FBH is also developing corresponding systems that use the two-photon transition at 778 nm and are expected to be promising candidates for global navigation satellite systems. In addition, the institute says they are used in optical calibration and as absolute frequency references in atom-based quantum technology.

Module for optical frequency references: Spectroscopy module with gas cell for an autonomous frequency reference (OFR) based on the D2 transition in rubidium at 780 nm. Image: FBH / P. Immerz


3-D quantum imaging

FBH is developing hybrid-integrated, miniaturized quantum light modules for mid-infrared (MIR) hyperspectral imaging and quantum OCT (optical coherence tomography). For this purpose, the researchers have developed special laser diodes and micro-optical elements that are integrated into a compact package together with a nonlinear optical crystal. These quantum light modules generate entangled photon pairs that interact in a nonlinear interferometer. This makes the technically challenging MIR spectral range accessible, with measurements made exclusively in the near-infrared range. According to the researchers, the entanglement means that neither detectors nor additional radiation sources are needed in the MIR.

Compact sensor head for 3D quantum imaging:  The sensor system can provide precise 3-D depth information in the mid-infrared and can be used for quantum OCT of ceramic and polymer materials. Image: FBH / A. Pubantz


Photonic integrated circuits

Photonic quantum computing uses light particles to generate and measure photonic resource states. Photonic cluster states provide a promising approach. Integrated photonic circuits will be used to perform the necessary quantum operations and generate the photonic cluster states. FBH says it has developed a photonic platform of AlGaN heterostructures for electro-optically controlled circuits suitable for fast and precise on-chip operations and measurements.
To realize computationally intensive resource states, one of the Joint Labs is investigating how to create photonic cluster states with optically active spin defects. The scientists are designing and fabricating nanophotonic spin-photon interfaces in diamond. For example, they recently fabricated a sawfish-like resonator that is expected to generate entangled photons with high efficiency. This has been shown in simulations and will now be confirmed experimentally.


Image: FBH / B. Schurian