A new scheme of a highly efficient hybrid laser cavity is proposed and experimentally demonstrated utilizing a hot cesium (Cs) vapor cell as an optical gain medium. The laser cavity consists of a macroscopic concave reflector (> 99% reflectivity) and a 4% Fresnel-reflecting facet of a single mode fiber (SMF). The cesium gain cell is located between these two reflectors. The SMF serves multiple roles: (1) a passive mode-matching component to approximate the pump beam diameter to that of the laser cavity mode within the cesium cell, (2) an output coupler with a low reflectivity, and (3) a low loss laser delivery with a high beam-quality. Optimizing the pump beam waist diameter and the cesium vapor cell temperature, a high slope efficiency of 86% and an optical-to-optical conversion efficiency of 71% were achieved in the pump power range of 400–600 mW. The unique multi-functional role of the SMF in the hybrid cavity is fully described, which can also be applied to other high optical gain media.

This study introduces a THz optical fiber with a petrolatum core and PTFE cladding, optimized for reduced bending losses and improved transmission, showcasing its potential in biomedical imaging with strong performance in tight bends. (c) 2024 The Author(s)

Alkali atomic vapor lasers have gained significant attention in recent decades as a promising option for high-powered and efficient laser systems. Utilizing hot alkali atomic vapor as the optical gain medium, these lasers, in principle, offer several advantages, such as high quantum efficiency, reduced thermal issues, and high beam quality. This paper reviews critical techniques developed in recent years to enhance the power and efficiency of these lasers. We discuss continuous wave laser optimization strategies, optical amplifier schemes, and pulsed laser generation based on hot alkali atomic vapor cells. Additionally, select findings from the authors’ research group are presented.

Whilst free space Bessel modes can show particle guidance over extended distances, this has been limited for fiber-based Bessel-like beams which have importance for microfluidic applications. We propose and experimen-tally demonstrate a novel all-fiber Bessel-like beam generator (BBG) that is shown transport a dielectric particle distance in excess of 2mm. This was achieved by optimizing the multimode interference (MMI) in the BBG struc-ture to create a Bessel-like beam of appropriate propagation invariant length (PIL) and judicious choice of laser wavelength suppress thermal effects. By varying the diameter of the region where the MMI occurred we analyzed its impact on PIL and the transverse intensity profile of the Bessel-like beam. Our study paves the way for the fiber optic applications such as novel beam shaping, optical transport, and optical imaging.

We experimentally demonstrated a tunable microsecond passively Q-switched fiber laser using deionized water (DIW) as a saturable absorber (SA). The DIW-SA was integrated into an all-fiber device by filling the gap between two cleaved fiber facets with DIW, which were enclosed in a glass ferrule. We observed a high nonlinear transmission through DIW-SA and implemented it in an erbium-doped fiber ring laser cavity. Microsecond Q-switched pulse trains were produced tunable from 1564.3 to 1603.4 nm using a fiber-optic Fabry-Perot interference filter within the cavity, avoiding peak water absorption while maintaining stable operation. Tunable and robust Q-switching of a fiber laser using water would open a new avenue of nonlinear aqua-photonics.

We present a fiber-optic sensor based on the principles of a Fabry–Perot interferometer (FPI), which promptly, sensitively, and precisely detects blood clot formation. This sensor has two types of sensor tips; the first was crafted by splicing a tapered fiber into a single-mode fiber (SMF), where fine-tuning was achieved by adjusting the tapered diameter and length. The second type is an ultra-compact blood FPI situated on the core of a single-mode fiber. The sensor performance was evaluated via clot-formation-indicating spectrum shifts induced by the varied quantities of a thrombin reagent introduced into the blood. The most remarkable spectral sensitivity of the micro-tip fiber type was approximately 7 nm/μL, with a power sensitivity of 4.1 dB/μL, obtained with a taper fiber diameter and length of 55 and 300 μm, respectively. For the SMF type, spectral sensitivity was observed to be 8.7 nm/μL, with an optical power sensitivity of 0.4 dB/μL. This pioneering fiber-optic thrombosis sensor has the potential for in situ applications, healthcare, medical monitoring, harsh environments, and chemical and biological sensing. The study underscores the scope of optical technology in thrombus detection, establishing a platform for future medical research and application.

We report the characteristics of GHz bandwidth amplified spontaneous emission (ASE) from a hot Cs atom vapor cell, where the optical feedback was inhibited. When pumped by an 852 nm laser, both forward and backward ASE output near 894 nm showed a nonlinear increase in its power without a pump power threshold. A continual decrease in spectral width down to 4.7 GHz was experimentally observed as the ASE output power increased. Using the same vapor cell, we injected a 1mW signal to configure a single-pass optical amplifier, and we monitored the forward output both in temporal and spectral domains. We found the signal laser efficiently suppressed the ASE and obtained a large amplification factor over 700 at the pump power of 1.2 W.

From mechanical syringes to electric field-assisted injection devices, precise control of liquid droplet generation has been sought after, and the present state-of-the-art technologies have provided droplets ranging from nanoliter to subpicoliter volume sizes. In this study, we present a new laser-driven method to generate liquid droplets with a zeptoliter volume, breaking the fundamental limits of previous studies. We guided an infrared laser beam through a hollow optical fiber (HOF) with a ring core whose end facet was coated with single-walled carbon nanotubes. The laser light was absorbed by this nanotube film and efficiently generated a highly localized microring heat source. This evaporated the liquid inside the HOF, which rapidly recondensed into zeptoliter droplets in the surrounding air at room temperature. We spectroscopically confirmed the chemical structures of the liquid precursor maintained in the droplets by atomizing dye-dissolved glycerol. Moreover, we explain the fundamental physical principles as well as functionalities of the optical atomizer and perform a detailed characterization of the droplets. Our approach has strong prospects for nanoscale delivery of biochemical substances in minuscule zeptoliter volumes.

We experimentally demonstrated an optimized diode-pumped cesium laser using frequency locking of a pump laser and quasi-continuous-wave pulse modulation to control both the pulse width and the repetition rate using fast mode-hopping in pump laser.

Objective: This study aimed to develop a tool to evaluate User Experience (UX) for the home appliance design. Background: Nowadays, UX is considered to be one of most important concepts to be considered by product designers. Home appliance product designers are trying to enhance the UX of their products to achieve competitive advantage across the industry. However, the number of UX evaluation tools that could be applied to home appliances is limited. It is needed to provide an UX evaluation tool to consider several different perspectives of UX such as usability, affective satisfaction, and value. Method: This study followed three stages. (1) UX design principles for home appliance were defined by literature review, web document analysis. (2) Design elements of home appliances are also defined through literature survey and product design property analysis. (3) UX design guidelines and UX evaluation questionnaires were generated based on the feasible combinations of these UX design principles and design elements. The generated questionnaires were filtered and merged into a total of 109 questionnaires by experts. Results: A UX evaluation tool for home appliance that consist of 109 questionnaires were developed. Application: The proposed UX evaluation tool could be useful for designers of home appliance industry to evaluate UX of their products and clarify the weak points of the designs.