Dec. 2, 2024
Liquid Optics
Human vision is a powerful inspiration for developers of advanced optical systems, with designers and engineers striving to replicate and even surpass its capabilities. Yet creating vision systems that deliver high magnification, small pixel sizes, and low f-numbers — especially in low-light conditions — poses substantial challenges. These factors tend to reduce the depth of field, necessitating precise focusing solutions. Traditional mechanical lenses often suffer from misalignment and wear over time, making them less reliable for high-speed, high-frequency applications. Liquid lenses offer a compelling solution to overcome these bottlenecks. Drawing on the dynamic focusing capabilities of the human eye, these lenses, constructed with a polymer membrane encasing optical fluid, adjust focus rapidly. Moreover, this technology enables reliable, precise focusing without mechanical wear and tear, and guaranteed performance for a billion re-focus cycles and well beyond. This article introduces liquid lenses, with a focus on their design, performance capabilities, applications, and prospects for continued success across sectors.
Key Technologies: Liquid Lenses, Voice Coil Actuation, Fast Steering Mirrors, Medical Imaging, Microscopy Imaging, Industrial Inspections, Barcode Scanning, 2D Mirrors, AR/VR Lenses
Specialty Optical Fiber
In the last two decades, the development of fiber lasers emitting in the 2µm region has been subject to comprehensive research. Compared to ytterbium-doped fiber lasers operating in the 1µm region, thulium-doped fiber laser sources are part of the well-known “eye safe” region starting from 1700 to 2200nm. These spectral region covers water absorption peaks and several atmospheric transmission windows which have raised the interest for medical, sensing, materials processing and direct energy applications. The two main pump bands for thulium-doped fibers are ~790 and ~1550nm. Pumping with 1550nm sources has the benefit of lowering the quantum defect with high laser efficiency and low threshold. However, laser diodes at this wavelength and with an output power >10W are not commonly available and alternative in-band pumping schemes had inherited lower optical efficiencies. The absorption band located at ~790nm overlaps with commercially available high power pump diodes, which under specific circumstances can enable a phenomenon known as two-for-one cross-relaxation process. The optimization of this process can facilitate the generation of two lasing photons for each pump photon, reaching a quantum efficiency up to 200% in the 2µm region. The high efficiency and excellent beam quality have made thulium-doped fiber lasers the perfect choice when a minimally invasive surgical technique is needed. Due to the characteristic absorption wavelengths of some materials, 2µm laser sources have turned into the choice for polymeric material processing applications. The constant growth on technological advancements in combination with power scalability as well as the permissible power transmission in free space, have also allowed the development of directed energy systems and other demanding applications for the 2µm fiber lasers.
Key Technologies: Fiber lasers, Specialty Optical Fiber, Optical Fiber in Medical Applications, Free Space Comms., Thulium-Doped Fiber Lasers
Low-Power Lasers
Despite their magnetic foundation, hard disk drives (HDDs) represent an emerging opportunity for the photonics industry. Heat-assisted magnetic recording (HAMR), the enabling mechanism behind HDDs, require the use of heat source -- and low-power lasers are a promising and effective candidate. This article overviews this developing application for low-power lasers in the realm of data communications and data storage, focusing on the types of sources used in this application and their integration into optimized systems. The use of lasers for the flipping, or “switching,” of data bits represents a shift from the established industry standard, perpendicular magnetic recording, in which a recording head’s write pole creates a perpendicular magnetic field to switch the recording media. The laser-based optical solution's benefits are examined, and real-world deployments are identified.
Key Technologies: NIR Lasers, Lasers in Data Communications, Fabry-Perot NIR Lasers, Waveguides, Optical Coupling, Femtosecond Lasers
Optoelectronic Sensors
The evolution of sensor technology has been pivotal in the advancement of various fields, including automotive safety, environmental monitoring, security, and more. Among these technologies, lidar and radar have emerged as leading tools thanks to their unique capabilities. But are these distinct modalities competitors, or teammates to be? This article from Silicon Austria Labs introduces the role that silicon photonics has to play in bridging the advantages of both techniques into a "unified" ranging sensor solution. As a combined system is introduced, the authors unravel challenges to miniaturization, component optimization, and best-use applications.
Key Technologies: Lidar (ToF and FMCW), Radar, ADAS, Silicon Photonics, VCSELs, MEMS, PICs, Multimode Interferometry
Photonic Fundamentals: Manufacturing Optics
Polymer refractive microlenses are finding expanded use in consumer, automotive, and electronics applications, among others. For small form factor modules, the commonly-used manufacturing process is based on UV lens molding at wafer level; while alternative lithography methods are limited in their ability to manufacture complex optical structures at wafer level, nanoimprint lithography (NIL) and lens molding are insensitive to shape and complexity, rendering them suitable for high-volume production. In this case study, partners DELO and EV Group report on how UV-curable polymers can offer a manufacturing boost for wafer-level micro-optics fabrication. Analyzed results reveal that NIL/lens molding (in combination) can be done on/with larger wafers, increasing UPH and production volumes while leveraging increasingly-reliable optical materials. Supported applications include automotive microlens arrays and others with very high reliability standards.
Key Technologies: Nanomprint Lithography, Micro-optics (components [DOEs, Surface Relief Gratings, Diffractive Waveguides] and fabrication), Adhesives, Polymer-Refractive Microlenses, UV light sources, UV Lens Molding, UV Lithography, Wafer-Level Optics
Laser Safety Column
Laser Safety columnist Ken Barat explores the origins, meaning, and utility of standard operating procedure (SOP). Its definition as outlined in Z136.1 Safe Use of Lasers Standard; Applicability in a range of settings, environments, and applications; and necessary renewals are among the topics that Barat explores.
Key Technologies: lasers, laser safety equipment
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