Marcus S. Dahlem

Laser instantaneous frequency (LIF) describes the time-varying frequency of a laser signal, defined as the temporal derivative of the oscillation phase divided by 2π. This concept is crucial in understanding frequency noise, phase noise, and chirped optical signals, where the frequency changes over time. Most current optical frequency measurements rely on frequency-domain analysis, which face limitations when applied to rapidly chirped lasers. Unlike frequency-domain methods, time-domain methods provide a more accurate representation of the time-varying frequency of chirped lasers, which is crucial for real-time applications. The widely used Hilbert transform-based method describes the LIF measurement but has slow real-time responses, a relatively low measurement speed, a not on-chip-compatible structure, and the ambiguity of the chirp sign, which hampers its use, particularly in real-time applications. This paper introduces a novel real-time LIF estimator for chirped lasers, offering higher accuracy, reduced algorithm complexity, and an on-chip integration solution. Experimental demonstrations include applications for FMCW LiDAR adaptive nonlinearity correction and real-time photoelectric control loops.

Light detection and ranging (LiDAR) sensors bring remarkable features to the automotive industry, enabling the development of autonomous vehicles. More concretely, frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR) sensors offer several advantages over their time-of-flight (ToF) counterparts in terms of maximum achievable distance, interference immunity, and velocity detection. Nonetheless, FMCW LiDAR systems are inevitably affected by phase noise, limiting the sensor performance. One evident solution consists in using narrow linewidth lasers, at the expense of overall sensor cost. Therefore, in this work, a thorough analysis of the phase noise is conducted for FMCW LiDAR sensors. Moreover, a novel and low-complex phase noise compensation algorithm based on pre-estimation and feedforward correction (PNC-PEFC) is proposed. The PNC-PEFC algorithm is extensively evaluated in an experimental setup under different target distances and additive white Gaussian noise (AWGN) conditions. The experimental results show excellent performance when applying the proposed PNC-PEFC algorithm, proving its robustness across all evaluated conditions.

We present the design and experimental evaluation of low-loss advanced bends in silicon nitride (SiN) waveguides for the C-band. The advanced bends, with a radius of 25 μm, exhibit a bending loss of approximately 0.025 dB per 90°, comparable to the loss of a circular bend with a radius of 50 μm. Consequently, the 25 μm radius advanced bend is proposed for routing in SiN photonic integrated circuits to reduce the overall footprint. Furthermore, the use of these advanced bends in micro ring resonators results in quality factors of 5.8×10³ and 5.5×10⁴, with relatively large free spectral ranges and extinction ratios for radii of 15 μm and 25 μm, respectively.

Sensors are integrated into collaborative robot systems to ensure the safety of human workers by allowing them to perceive their environments, detect human presence, and adjust their actions accordingly. This PRISMA scoping review focuses on current sensor-enabled safety systems for human-robot collaboration in the manufacturing industry based on both scientific papers and patents. From the initial search of 6669 references, 281 underwent full-text review and segmentation based on sensor technology, installation location, and safety operating mode according to the ISO/TS 15066 standard. In the last decade, there has been a clear trend of increasing sensor-enabled safety systems. The dominant sensors used are infrared-structured light, capacitive, LiDAR, resistive, stereo/depth camera, RaDAR, and laser scanners. The primary safety operating mode identified was Speed and Separation Monitoring (SSM). Some systems integrate multiple sensor types, with the most common combinations being LiDAR with stereo cameras or LiDAR with capacitive sensors, and laser scanners with RaDAR. We suggest multi-sensor integration and standardized benchmarks for future development. This review is among the few that employ the PRISMA protocol to study sensor technologies and contribute to a more systematic understanding of the current state of the art in this area.

In this paper we study the gas sensing performance of a compact silicon photonics Mach-Zehnder interferometer (MZI) with a coiled sensing arm. A partially exposed sensor was fabricated using deep UV lithography, with a process resolution of 248 nm. Testing with inert gases, He and N $_{2}$ , resulted in a measured sensitivity and limit of detection of $\sim\!$ 1458 nm/RIU and $\sim$ 8.5×10 ^-5 RIU, respectively, in a sensing volume of 1.852 picoliters. The temperature sensitivity of the sensor was 166 pm/ $^\circ$ C and the inclusion of a cladded ring-resonator, post-MZI, allowed resolving the temperature drift due to gas flow. In order to further enhance the overlap of the optical mode with the measurand and thus the sensitivity, a suspended MZI was designed and simulated with an expected sensitivity of $\sim$ 5500 nm/RIU, for wavelengths around 1550 nm and a temperature of 300 K.

Optical phase errors are inherent to practical waveguides and will degrade the beam quality of optical phased arrays. This paper demonstrates a scalable approach to on-chip phase calibration of optical phased arrays using a compact phase interrogator structure. This phase interrogator is designed for optical phased arrays with a 2.5μm pitch and demonstrated in a 64-channel optical phased array realized in a Si/SiN photonic stack. The optical phased array exhibits 38° of unambiguous beam steering range and a side lobe level of at most -9.8 dB after calibration. The calibration algorithm is model-based and does not rely on any iterative optimization algorithm. This enables calibration with linear scaling of both the computational complexity and the area of the calibration structures. By including wavelength dependent effects, the model allows for 2D beam steering without any need for re-calibration.

In this work, we summarize our recent advances in 2D beamsteering using optical phased arrays operating in NIR and SWIR wavelengths, covering different architectures and steering techniques based on active phase shifting and wavelength tuning.

Integrated photonic is penetrating different segments of the commercial market beyond classical tele/datacom where it provides distinct features such as compactness, low cost, reliability and robustness. In this talk we will focus on these aspects and couple of applications will be introduced. Solid-state lidar has been an exciting research topic for quite a while. And now it’s finding its way into commercial products. Especially automotive applications, such as ADAS technologies, are craving compact, robust and inexpensive systems for 3D mapping.

We demonstrate a compact ( $367 \times 67 \, \mu {\text{m}}^2$ ) four-channel wavelength division multiplexer using an arrayed waveguide grating based on multimode interference couplers, and built on a monolithic silicon photonics platform. The design is particularly attractive due to the thin device layer. A semi-numerical approach was used for device design and simulation. Optical measurements were found to be consistent with simulation results. The device channel spacing, 3-dB bandwidth and crosstalk were measured to be 97 GHz, 87 GHz and 9.6 dB, respectively, for the designed wavelength of operation near 1310 nm.