arXiv subjects

Konstantinos Akritidis

Publications and source records attributed to Konstantinos Akritidis.

5 recordsLinked to original sources

arXiv2026

Micro-transfer Printed Blue InGaN Lasers on Silicon Nitride Photonic Integrated Circuits

Expanding integrated photonics into the blue spectral range requires high-performance light sources, making the gallium nitride (GaN) material family indispensable. While silicon nitride (SiN) platforms offer a robust, CMOS compatible passive ecosystem for visible wavelengths, seamlessly integrating GaN lasers remains a major bottleneck. Conventional heterogeneous integration methods present distinct trade-offs: full-wafer bonding achieves high throughput but requires careful management of thermal and lattice mismatches across large areas, whereas flip-chip bonding ensures high yield through pretesting but is constrained by sequential processing speed. In this landscape, micro-transfer printing (MTP) emerges as a disruptive, material-efficient alternative, bypassing these limitations by combining high-density parallel integration with known-good-die selection. Applying MTP to GaN, however, presents a significant material challenge: due to its chemical inertness and strong III-N bonds, device release typically relies on electrochemical etching, which can compromise material quality. Here, we overcome this hurdle and demonstrate the first micro-transfer printed blue lasers on a SiN platform. Using a heavily doped n-type sacrificial layer together with optimized electrochemical etching conditions, we release smooth-surfaced thin-film light sources from bulk GaN substrates. Following release, the devices are integrated and butt-coupled to SiN fork-shaped edge couplers, achieving high current densities exceeding 20 kA$/$cm$^2$ alongside lasing at 455 nm. These results expand the visible integrated photonic toolkit and establish a framework for multi-wavelength integration, opening new avenues for next-generation technologies including flow cytometry, quantum computing, optical communications, and augmented/virtual reality.

physics.optics↗

arXiv2026

Heterogeneously Integrated Efficient and Widely Tunable Lasers at 795 nm for Rubidium-Based Quantum Technologies

Scaling quantum processors and optical atomic clocks fundamentally requires orders-of-magnitude reductions in the size, weight, power, and cost of optical control systems. Photonic integration of lasers is critical to fulfill these requirements. At the near-infrared wavelengths required for atomic clocks and quantum computing through manipulation of rubidium atoms, laser integration is hindered by difficulty in light coupling and poor heat dissipation. Here, we introduce a wafer-scalable method utilizing micro-transfer printing to integrate GaAs-based amplifiers in etched recesses, directly butt-coupled to silicon nitride waveguides. We demonstrate extended-cavity single-mode lasers using this integration approach. Our compact microgear laser achieves a narrow 3 kHz fundamental linewidth at an on-chip output power of >22 mW -- a record for a single-mode heterogeneously integrated laser in the 780-800 nm band -- with a wall-plug efficiency of 9.4%, showcasing the high-power and efficiency potential of this integration approach. Additionally, we demonstrate a widely tunable laser leveraging Vernier filters to achieve lasing with 9 nm coarse tuning, a quasi-continuous fine-tuning range exceeding 140 GHz, and a mode-hop-free tuning range of 45 GHz. Our scalable integrated laser toolkit shows great promise for replacing macroscopic external-cavity diode lasers in next-generation quantum technologies and optical atomic clocks.

physics.optics↗

arXiv2026

A Heterogeneous 200 mm Silicon Nitride Photonics Platform for Visible-to-Near-Infrared Applications via Micro-Transfer Printing

The commercialization of next-generation technologies, including optical interconnects, quantum computing, AR/VR, and medical diagnostics, requires a low-loss photonic platform offering compact, multifunctional systems in the visible and near-infrared range. Although silicon nitride (SiN) is an excellent material due to its ultra-low loss and broad transparency window, integrating active components such as light sources, modulators and photodetectors from diverse material platforms in a scalable, reliable way remains challenging. Micro-transfer printing is an emerging wafer-scale heterogeneous integration technology that can be implemented as a back-end post-processing step without disrupting the primary in-line fabrication process. In this work, we present a dual LPCVD SiN layer platform fabricated in a 200 mm CMOS pilot line, that incorporates micro-transfer printing modules, allowing the integration of active components on well defined recesses. A hydrogenated amorphous silicon layer is also available to increase the versatility of the platform allowing for evanescently-coupled III-V lasers as well as other passive functionality in the near-infrared region. We report full wafer-scale measurements showing low optical SiN losses of 4 dB/cm and 0.23 dB/cm at a wavelength of 488 nm and 940 nm respectively. In addition, a transition loss of only 0.35 dB is obtained from the SiN to the a-Si:H layer, in good agreement with simulated values. Finally, to showcase more advanced functionality, GaAs-based gain sections are micro-transfer printed on several dies, achieving consistent die-to-die lasing at 970 nm with on-chip optical powers of approximately 1 mW. These results showcase the potential of the integrated photonics platform towards unlocking a wide range of new applications in the sub-1-$μ$m spectral region.

physics.optics↗

arXiv2026

Thin-film lithium tantalate for ultraviolet integrated electro-optic modulator

The realization of integrated, high-speed ultraviolet (UV) modulation is pivotal for the advancement of quantum information processing, portable atomic clocks, and secure solar-blind communications. While mature photonic platforms have facilitated sophisticated system-level integration across visible and infrared spectra, high-speed active modulation in UV remains with traditional bulk crystals. Consequently, a scalable integrated solution that simultaneously combines low insertion loss and extreme compactness with high modulation efficiency has remained challenging. Here, we report the first integrated UV electro-optic modulator on a thin-film lithium tantalate (TFLT) platform. By employing a compact lumped-electrode design, we achieve a record-low VπL of 85 mV\cdot cm at 375 nm, providing an up to four orders of magnitude improvement in terms of bandwidth/Vπ L over bulk technologies. The device demonstrates a robust extinction ratio of 22.7 dB, a low insertion loss of 1.3 dB, and a Vπ of 4.2V. Although the measured 3-dB bandwidth of 922 MHz is currently limited by photodetector performance, the small device footprint of 1.16 mm and electrode design of 200 μm indicate intrinsic potential for high-speed operation beyond 67 GHz which is confirmed by the electrical-to-electrical response. This work establishes TFLT as a disruptive platform for wafer-scale compatible active UV photonics, enabling the next generation of scalable quantum and communication systems.

physics.optics↗

arXiv2025

Micro-Transfer Printed Continuous-Wave and Mode-Locked Laser Integration at 800 nm on a Silicon Nitride Platform

Applications such as augmented and virtual reality (AR/VR), optical atomic clocks, and quantum computing require photonic integration of (near-)visible laser sources to enable commercialization at scale. The heterogeneous integration of III-V optical gain materials with low-loss silicon nitride waveguides enables complex photonic circuits with low-noise lasers on a single chip. Previous such demonstrations are mostly geared towards telecommunication wavelengths. At shorter wavelengths, limited options exist for efficient light coupling between III-V and silicon nitride waveguides. Recent advances in wafer-bonded devices at these wavelengths require complex coupling structures and suffer from poor heat dissipation. Here, we overcome these challenges and demonstrate a wafer-scale micro-transfer printing method integrating functional III-V devices directly onto the silicon substrate of a commercial silicon nitride platform. We show butt-coupling of efficient GaAs-based amplifiers operating at 800 nm with integrated saturable absorbers to silicon nitride cavities. This resulted in extended-cavity continuous-wave and mode-locked lasers generating pulse trains with repetition rates ranging from 3.2 to 9.2 GHz and excellent passive stability with a fundamental radio-frequency linewidth of 519 Hz. These results show the potential to build complex, high-performance fully-integrated laser systems at 800 nm using scalable manufacturing, promising advances for AR/VR, nonlinear photonics, timekeeping, quantum computing, and beyond.

physics.optics↗