The crystallinity of a material often plays a significant role in determining its material properties. Aluminum nitride (AlN), which has emerged as a promising material for photonics in the past few decades, can be polycrystalline or monocrystalline in nature. Previously, the electro-optic (EO) coefficient of polycrystalline and bulk monocrystalline AlN has been reported. However, to the best of our knowledge, the EO coefficient of thin-film monocrystalline AlN has not yet been reported. In this work, we report the EO coefficient of thin-film monocrystalline AlN and make a side-by-side comparison with the EO coefficient of polycrystalline AlN. We used the resonant shift of a microring resonator to measure the EO coefficients for both transverse electric (TE) and transverse magnetic (TM) modes in the telecom C-band. For monocrystalline AlN, we observe surface effects that cause bias drift, which can be eliminated through annealing. The EO coefficients we measured for monocrystalline and polycrystalline AlN are comparable, with the EO of annealed monocrystalline AlN being slightly higher.

We present Self-Aligned Fiber Entry Low-loss Optical Couplers (SAFELOCs), three-dimensionally tapered polymer waveguides that efficiently couple tapered optical fibers to on-chip waveguides across multiple material platforms with low insertion loss (≲ 1 dB) over the C and L -bands. SAFELOCs incorporate 3D fiber receptacles for passive, mechanical alignment, enabling broadband coupling without precision stages or active feedback. Experimental measurements confirm low insertion loss consistent with simulations, and the design can achieve minimal polarization dependence. The tapered fiber receptacle also allows permanent fiber attachment while expanding alignment tolerance, facilitating simultaneous coupling of fiber arrays for multi-port photonic circuits. While demonstrated in the C and L bands on Si₃N₄, Si, and SU-8, the two-photon lithography fabrication process can be applied to other materials, and the polymer's broad transparency window suggests compatibility down to 400 nm, highlighting the versatility and scalability of SAFELOCs.

We demonstrate efficient coupling of multiple fibers using 3D-printed coupling structures that interface with on-chip grating and adiabatic couplers, achieving low-loss, compact integration. The technique is readily scalable for high-density and alignment-tolerant photonic packaging applications.

We present SOI foundry-compatible, switchable, and nonvolatile micromechanical beams for post-fabrication tuning of microresonator-based photonic integrated circuits. Utilizing mechanical bistability, these devices provide an energy-efficient, passive, and digital approach for aligning optical resonances to target wavelengths.

We experimentally measure the optomechanical coupling in a suspended AlN ring cavity. Comparisons with simulations and external piezo-optical measurements suggest a significant role of an indirect photoelastic interaction, governed by piezoelectric and electrooptic effects.

We demonstrate an adiabatic polarization splitter-rotator on a 500 nm Si 3 N 4 -on-SiO 2 platform, with < 1 dB insertion loss, < −12 dB crosstalk, and > 50 nm bandwidth near 1550 nm, tolerant to ±50 nm width variations.

Using the resonant shift in a microring resonator, we measure the electro-optic coefficient for both TE and TM modes in monocrystalline and polycrystalline AlN in the C band.

We present an ultrasensitive technique for probing transient optical changes in atomically thin molybdenum disulfide (MoS_2) layers integrated onto silicon nitride (Si_3N_4) ring resonators. The MoS_2 is illuminated by a femtosecond laser, while a tunable near-infrared (NIR) continuous-wave laser probes the microresonator resonance. The NIR light polarization can be adjusted to either transverse electric (TE, parallel to the 2D material) or transverse magnetic (TM, perpendicular), a configuration that is impossible to achieve with conventional normal-incidence pump-probe techniques. By capturing the transmitted signal on a fast oscilloscope, we detect transient optical shifts with unprecedented sensitivity, observing phenomena over time scales ranging from picoseconds to microseconds. Our results reveal both a rapid, carrier-induced nonlinear optical shift in the resonance, and a slower thermo-optic transient. The ability to simultaneously measure these fast and slow dynamics offers new insight into the complex optoelectronic behavior of 2D materials when integrated with microresonators. This method provides a significant advance over traditional pump-probe approaches, enabling the detection of exceedingly small transient signals and opening new avenues for exploring the optical properties of atomically thin materials. Our findings highlight the potential of this approach for investigating polarization-dependent nonlinear effects, with applications in photonics, sensing, and optoelectronics.

We measured the optical transmission through an SU-8 microring resonator inside a cryostat and analyzed the shift of the resonant wavelengths to determine the thermo-optic behavior around a wavelength of 1600 nm. As the temperature was decreased from room temperature (RT) to 3K, the refractive index of crosslinked SU-8 was measured to increase from 1.571 to 1.584, while the thermo-optic coefficient decreased by two orders of magnitude.

We demonstrate low-loss (< 1 dB), broadband (BW∼100 nm near λ ∼ 1550 nm) and polarization-independent fiber-to-chip couplers using 3D nano-printed polymer structures on Si3N4-on-SiO2 platform.

This paper demonstrates a passive, integrated electro-optic receiver for detection of free -space microwave radiation. Unlike a traditional microwave receiver, which relies on conductive antennas and electrical amplifiers, this receiver uses only passive, optically probed elements with no electrodes or electronic components. The receiver employs two co -resonant structures: a dielectric resonator antenna (DRA) to concentrate incoming microwave radiation and an integrated aluminum nitride (AlN) racetrack resonator to resonantly enhance the optical carrier. The microwave field of the DRA modulates the built-up optical carrier in the resonator via the electro-optic response of AlN. We successfully detected 15 GHz microwave radiation through co -resonant electro-optic up -conversion, without the need for any conducting electrodes, amplifiers, or electronic components. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

We designed and demonstrated 3D polymer coupler structures to adiabatically couple light into polymer waveguides. We measured a coupling loss of 2.1 dB per coupler facet around 1550 nm.

Here we use the near field of a dielectric resonant antenna to modulate an on-chip aluminum nitride ring resonator. Using this device we demonstrate entirely metal-free electro-optic modulation at 15.1 GHz.

We report a fabrication-tolerant and broad-band polarization rotator implemented on the SiN platform. Numerical studies predict approximately 99.7% polarization conversion efficiency for a device length of 185 micrometres. Preliminary experimental work suggests 90% conversion efficiency across the 1520-1620 nm waveband.

We employ a silicon nitride microdisk resonator to observe the transient dynamics of photoexcited carriers in multi-layer and few-layer MoS 2 exfoliated flakes.

We demonstrate an AlN piezo-opto-mechanical slot-mode resonator excited using a radio-frequency electrode hovering above the chip, with a 1550-nm optical mode coupling to multiple mechanical modes over broad frequency span (4.5 MHz - 3.8 GHz).

Superconducting computing research is motivated by fast energy-efficient computing, which creates the challenge of developing components with low-power dissipation requirements. In support of this research, we demonstrate a system that measures heat dissipated by electrical and absorbed optical power in packaged cryogenic devices at a temperature of 4 K. In our system, the device under test resides on a stage that is maintained at a constant 4 K using a feedback heater circuit. The sample stage is cooled via a passive weak thermal link to a stabilized 3 K bath of a closed-cycle pulsed-tube refrigerator. With a maximum device payload of 300 g and a weak thermal link of 13 800 K/W, the empirically determined minimum measurable dissipated power is 300 pW. With a very strong thermal link of 53 K/W, the maximum measurable dissipated power is 30 mW.

We report for the first time the thermo-optic behavior of SU-8 around 1550nm in a ring resonator from 300K to 3K. Cryogenic measurement is enabled by on-chip 3D polymer structures that secure the fiber-to-chip coupling.

To inform research activities in HPC interconnect of strategic importance to the USG beyond 2018, in January of 2018, the DoD sponsored the 2nd Photonics and Electronics Technology for Extreme-scale Computing (REPETE) workgroup. REPETE investigated new challenges in the area of HPC interconnect inspired by technology trends and challenges of vital importance to USG stakeholders. The REPETE Working group investigated two focus areas of interest to the USG: Socket Level Photonic IO and Cryogenic Photonic IO. The working group spanned industry, academia, and government, in research, development, product, and technology investment areas. The workgroup team focusing on current and future design challenges for socket level photonic IO began discussing technical challenges and current state of applying photonics to off-chip IO in April of 2019 through biweekly meetings that concluded in early September of 2019. The focus of these meetings was to discuss what technology exists for moving the conversion of electrical signaling to photonic signaling from the node (as is currently done) down to within the socket for off-chip IO. Areas discussed include: I/O Requirements and Trends at the Compute Socket for 2025 and Beyond; Current and Near-Term Copper Solutions for Off-Chip, Socket-Level Interconnect; Current Photonic Solutions for Off-Chip or Socket-Level Interconnect; Light Generation for Off-Chip, Socket-Level IO; Fabrication and Packaging of Photonic Integrated Circuits; All-Photonic Switching Technology; and Simulation of Photonic Interconnects.

The property of self-imaging combined with the polarization birefringence of the angled multimode waveguide is used to design a silicon nitride (SiN) polarization splitter (PS) at lambda similar to 1550 nm. The demonstrated PS on a 450 nm thick SiN device layer (with 2.5 mu m cladding oxide) has a footprint of 80 mu mx13 mu m and exhibits nearly wavelength independent performance over the C+L bands. Also, the device can be configured as a polarization combiner (PC) in reverse direction with similar bandwidth and performance. The measured crosstalk (CT) and insertion loss (IL) are respectively <-18 dB (<-20 dB) and similar to 0.7 dB (similar to 0.8 dB) for TE (TM) polarization over the measurement wavelength range of 1525 nm <= lambda <= 1625 nm. The measured device parameter variations suggest some tolerance to fabrication variations. Such a device is a good candidate for a photonics integrated chip (PIC) foundry-compatible, SiN PS. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement