Silicon-photonics-enabled chip-based 3D printer.

Imagine if it were possible to create 3D objects in the palm of your hand within seconds using only a single photonic chip. Although 3D printing has revolutionized the way we create in nearly every aspect of modern society, current 3D printers rely on large and complex mechanical systems to enable layer-by-layer addition of material. This limits print speed, resolution, portability, form factor, and material complexity. Although there have been recent efforts in developing novel photocuring-based 3D printers that utilize light to transform matter from liquid resins to solid objects using advanced methods, they remain reliant on bulky and complex mechanical systems. To address these limitations, we combine the fields of silicon photonics and photochemistry to propose the first chip-based 3D printer. The proposed system consists of only a single millimeter-scale photonic chip without any moving parts that emits reconfigurable visible-light holograms up into a simple stationary resin well to enable non-mechanical 3D printing. Furthermore, we experimentally demonstrate a stereolithography-inspired proof-of-concept version of the chip-based 3D printer using a visible-light beam-steering integrated optical phased array and visible-light-curable resin, showing 3D printing using a chip-based system for the first time. This work demonstrates the first steps towards a highly-compact, portable, and low-cost solution for the next generation of 3D printers.

Mechanically-flexible wafer-scale integrated-photonics fabrication platform.

The field of integrated photonics has advanced rapidly due to wafer-scale fabrication, with integrated-photonics platforms and fabrication processes being demonstrated at both infrared and visible wavelengths. However, these demonstrations have primarily focused on fabrication processes on silicon substrates that result in rigid photonic wafers and chips, which limit the potential application spaces. There are many application areas that would benefit from mechanically-flexible integrated-photonics wafers, such as wearable healthcare monitors and pliable displays. Although there have been demonstrations of mechanically-flexible photonics fabrication, they have been limited to fabrication processes on the individual device or chip scale, which limits scalability. In this paper, we propose, develop, and experimentally characterize the first 300-mm wafer-scale platform and fabrication process that results in mechanically-flexible photonic wafers and chips. First, we develop and describe the 300-mm wafer-scale CMOS-compatible flexible platform and fabrication process. Next, we experimentally demonstrate key optical functionality at visible wavelengths, including chip coupling, waveguide routing, and passive devices. Then, we perform a bend-durability study to characterize the mechanical flexibility of the photonic chips, demonstrating bending a single chip 2000 times down to a bend diameter of 0.5 inch with no degradation in the optical performance. Finally, we experimentally characterize polarization-rotation effects induced by bending the flexible photonic chips. This work will enable the field of integrated photonics to advance into new application areas that require flexible photonic chips.

Integrated visible-light polarization rotators and splitters for atomic quantum systems.

In this work, we design and experimentally demonstrate the first, to the best of our knowledge, integrated polarization splitters and rotators at blue wavelengths. We develop compact and efficient designs for both a polarization splitter and rotator at a 422-nm wavelength, an important laser-cooling transition for 88Sr+ ions. These devices are fabricated in a 200-mm wafer-scale process and experimentally demonstrated, resulting in a measured polarization-splitter transverse-electric thru-port coupling of 98.0% and transverse-magnetic tap-port coupling of 77.6% for a compact 16-µm-long device and a polarization-rotator conversion efficiency of 92.2% for a separate compact 111-µm-long device. This work paves the way for more sophisticated integrated control of trapped-ion and neutral-atom quantum systems.

Integrated liquid-crystal-based variable-tap devices for visible-light amplitude modulation.

In this Letter, we propose and experimentally demonstrate the first, to our knowledge, integrated liquid-crystal-based (LC-based) variable-tap devices for visible-light amplitude modulation. These devices leverage the birefringence of LC medium to actively tune the coupling coefficient between two waveguides. First, we develop the device structure, theory of operation, and design procedure. Next, we summarize the fabrication and LC packaging procedure for these devices. Finally, we experimentally demonstrate amplitude modulation with 15.4-dB tap-port extinction within ±3.1 V for a 14-µm-long device at a 637-nm operating wavelength. These small-form-factor variable-tap devices provide a compact and low-power solution to integrated visible-light amplitude modulation and will enable future high-density integrated visible-light systems.

Hands-On Photonic Education Kits: empowering the integrated photonics workforce through practical training.

The Hands-On Photonic Education (HOPE) Kits, developed with AIM Photonics, address the need for skilled workers in integrated photonics. This paper highlights the role of the HOPE Kits in advancing the training ecosystem and bridging the skills gap. The kits include fully packaged photonic integrated circuits (PICs), enabling instructors to educate and train students on PIC testing and characterization. Covering a wide range of devices and circuits, from waveguides to wavelength division multiplexing for data communication, the kits offer a hands-on experience. Engaging with actual PICs, students gain practical insights, enhancing their understanding of key principles, and preparing them for real-world skill sets in integrated photonics.

Liquid-crystal-based visible-light integrated optical phased arrays and application to underwater communications.

In this Letter, we present the first, to the best of our knowledge, liquid-crystal-based integrated optical phased arrays (OPAs) that enable visible-light beam forming and steering. A cascaded OPA architecture is developed and experimentally shown to emit a beam in the far field at a 632.8-nm wavelength with a power full width at half maximum of 0.4°×1.6° and 7.2° beam-steering range within ±3.4 V. Furthermore, we show the first visible-light integrated-OPA-based free-space-optical-communications transmitter and use it to demonstrate the first integrated-OPA-based underwater-wireless-optical-communications link. We experimentally demonstrate a 1-Gbps on-off-keying link through water and an electronically-switchable point-to-multipoint link with channel selectivity greater than 19 dB through a water-filled tank.

Impact of process variations on splitter-tree-based integrated optical phased arrays.

We consider the impact of intra-wafer systematic spatial variation, pattern density mismatch, and line edge roughness on splitter-tree-based integrated optical phased arrays. These variations can substantially affect the emitted beam profile in the array dimension. We study the effect on different architecture parameters, and the analysis is shown to be consistent with experimental results.

Integrated visible-light liquid-crystal-based phase modulators.

In this work, an integrated liquid-crystal-based phase modulator operating at visible wavelengths was developed and experimentally demonstrated. A visible-light silicon-nitride-based 300-mm-wafer foundry platform and a liquid-crystal integration process were developed to leverage the birefringence of liquid crystal to actively tune the effective index of a section of silicon-nitride waveguide and induce a phase shift over its length. The device was experimentally shown to achieve a 41π phase shift within 4.8 Vpp for a 500-µm-long modulator, which means that a 2π phase shifter would need to be only 24.4 µm long. This device is a compact and low-power solution to the challenge of integrated phase modulation in silicon nitride and paves the way for future low-power small-form-factor integrated systems at visible wavelengths.

A Silicon Photonic Data Link with a Monolithic Erbium-Doped Laser.

To meet the increasing demand for data communication bandwidth and overcome the limits of electrical interconnects, silicon photonic technology has been extensively studied, with various photonics devices and optical links being demonstrated. All of the optical data links previously demonstrated have used either heterogeneously integrated lasers or external laser sources. This work presents the first silicon photonic data link using a monolithic rare-earth-ion-doped laser, a silicon microdisk modulator, and a germanium photodetector integrated on a single chip. The fabrication is CMOS compatible, demonstrating data transmission as a proof-of-concept at kHz speed level, and potential data rate of more than 1 Gbps. This work provides a solution for the monolithic integration of laser sources on the silicon photonic platform, which is fully compatible with the CMOS fabrication line, and has potential applications such as free-space communication and integrated LIDAR.

Optical frequency synthesizer with an integrated erbium tunable laser.

Optical frequency synthesizers have widespread applications in optical spectroscopy, frequency metrology, and many other fields. However, their applicability is currently limited by size, cost, and power consumption. Silicon photonics technology, which is compatible with complementary-metal-oxide-semiconductor fabrication processes, provides a low-cost, compact size, lightweight, and low-power-consumption solution. In this work, we demonstrate an optical frequency synthesizer using a fully integrated silicon-based tunable laser. The synthesizer can be self-calibrated by tuning the repetition rate of the internal mode-locked laser. A 20 nm tuning range from 1544 to 1564 nm is achieved with ~10-13 frequency instability at 10 s averaging time. Its flexibility and fast reconfigurability are also demonstrated by fine tuning the synthesizer and generating arbitrary specified patterns over time-frequency coordinates. This work promotes the frequency stability of silicon-based integrated tunable lasers and paves the way toward chip-scale low-cost optical frequency synthesizers.

Monolithically integrated erbium-doped tunable laser on a CMOS-compatible silicon photonics platform.

A tunable laser source is a crucial photonic component for many applications, such as spectroscopic measurements, wavelength division multiplexing (WDM), frequency-modulated light detection and ranging (LIDAR), and optical coherence tomography (OCT). In this article, we demonstrate the first monolithically integrated erbium-doped tunable laser on a complementary-metal-oxide-semiconductor (CMOS)-compatible silicon photonics platform. Erbium-doped Al2O3 sputtered on top is used as a gain medium to achieve lasing. The laser achieves a tunability from 1527 nm to 1573 nm, with a >40 dB side mode suppression ratio (SMSR). The wide tuning range (46 nm) is realized with a Vernier cavity, formed by two Si3N4 microring resonators. With 107 mW on-chip 980 nm pump power, up to 1.6 mW output lasing power is obtained with a 2.2% slope efficiency. The maximum output power is limited by pump power. Fine tuning of the laser wavelength is demonstrated by using the gain cavity phase shifter. Signal response times are measured to be around 200 µs and 35 µs for the heaters used to tune the Vernier rings and gain cavity longitudinal mode, respectively. The linewidth of the laser is 340 kHz, measured via a self-delay heterodyne detection method. Furthermore, the laser signal is stabilized by continuous locking to a mode-locked laser (MLL) over 4900 seconds with a measured peak-to-peak frequency deviation below 10 Hz.

Publisher Correction: Integrating photonics with silicon nanoelectronics for the next generation of systems on a chip.

In this Letter, owing to an error during the production process, the author affiliations were listed incorrectly. Affiliation number 5 (Colleges of Nanoscale Science and Engineering, State University of New York (SUNY)) was repeated, and affiliation numbers 6-8 were incorrect. In addition, the phrase "two oxide thickness variants" should have been "two gate oxide thickness variants". These errors have all been corrected online.

Integrating photonics with silicon nanoelectronics for the next generation of systems on a chip.

Electronic and photonic technologies have transformed our lives-from computing and mobile devices, to information technology and the internet. Our future demands in these fields require innovation in each technology separately, but also depend on our ability to harness their complementary physics through integrated solutions1,2. This goal is hindered by the fact that most silicon nanotechnologies-which enable our processors, computer memory, communications chips and image sensors-rely on bulk silicon substrates, a cost-effective solution with an abundant supply chain, but with substantial limitations for the integration of photonic functions. Here we introduce photonics into bulk silicon complementary metal-oxide-semiconductor (CMOS) chips using a layer of polycrystalline silicon deposited on silicon oxide (glass) islands fabricated alongside transistors. We use this single deposited layer to realize optical waveguides and resonators, high-speed optical modulators and sensitive avalanche photodetectors. We integrated this photonic platform with a 65-nanometre-transistor bulk CMOS process technology inside a 300-millimetre-diameter-wafer microelectronics foundry. We then implemented integrated high-speed optical transceivers in this platform that operate at ten gigabits per second, composed of millions of transistors, and arrayed on a single optical bus for wavelength division multiplexing, to address the demand for high-bandwidth optical interconnects in data centres and high-performance computing3,4. By decoupling the formation of photonic devices from that of transistors, this integration approach can achieve many of the goals of multi-chip solutions 5 , but with the performance, complexity and scalability of 'systems on a chip'1,6-8. As transistors smaller than ten nanometres across become commercially available 9 , and as new nanotechnologies emerge10,11, this approach could provide a way to integrate photonics with state-of-the-art nanoelectronics.

Programmable dispersion on a photonic integrated circuit for classical and quantum applications.

We demonstrate a large-scale tunable-coupling ring resonator array, suitable for high-dimensional classical and quantum transforms, in a CMOS-compatible silicon photonics platform. The device consists of a waveguide coupled to 15 ring-based dispersive elements with programmable linewidths and resonance frequencies. The ability to control both quality factor and frequency of each ring provides an unprecedented 30 degrees of freedom in dispersion control on a single spatial channel. This programmable dispersion control system has a range of applications, including mode-locked lasers, quantum key distribution, and photon-pair generation. We also propose a novel application enabled by this circuit - high-speed quantum communications using temporal-mode-based quantum data locking - and discuss the utility of the system for performing the high-dimensional unitary optical transformations necessary for a quantum data locking demonstration.

Integrated optical phased arrays for quasi-Bessel-beam generation.

Integrated optical phased arrays for generating quasi-Bessel beams are proposed and experimentally demonstrated in a CMOS-compatible platform. Owing to their elongated central beams, Bessel beams have applications in a range of fields, including multiparticle trapping and laser lithography. In this Letter, continuous Bessel theory is manipulated to formulate the phase and amplitude conditions necessary for generating free-space-propagating Bessel-Gauss beams using on-chip optical phased arrays. Discussion of the effects of select phased array parameters on the generated beam's figures of merit is included. A one-dimensional splitter-tree-based phased array architecture is modified to enable arbitrary passive control of the array's element phase and amplitude distributions. This architecture is used to experimentally demonstrate on-chip quasi-Bessel-beam generation with a ∼14 mm Bessel length and ∼30 µm power full width at half maximum.

Finite-difference complex-wavevector band structure solver for analysis and design of periodic radiative microphotonic structures.

We demonstrate a finite-difference approach to complex-wavevector band structure simulation and its use as a tool for the analysis and design of periodic leaky-wave photonic devices. With the (usually real) operating frequency and unit-cell refractive index distribution as inputs, the eigenvalue problem yields the complex-wavevector eigenvalues and Bloch modes of the simulated structure. In a two-dimensional implementation for transverse-electric fields with radiation accounted for by perfectly matched layer boundaries, we validate the method and demonstrate its use in simulating the complex-wavevector band structures and modal properties of a silicon photonic crystal waveguide, an array-antenna-inspired grating coupler with unidirectional radiation, and a recently demonstrated low-loss Bloch-mode-based waveguide crossing array. Additionally, we show the first direct solution of the recently proposed open-system low-loss Bloch modes. We expect this method to be a valuable tool in photonics design, enabling the rigorous analysis and synthesis of advanced periodic and quasi-periodic photonic devices.