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Optics Components and Electronic Equipment
Published in Vadim Backman, Adam Wax, Hao F. Zhang, A Laboratory Manual in Biophotonics, 2018
Vadim Backman, Adam Wax, Hao F. Zhang
The laser beam in a laser pointer is often generated by a laser diode, which uses a semiconductor as the gain medium. Specifically, the semiconductor consists of a P-N junction, made from doping two thin layers on the surface of a wafer. The top layer is doped to be a P-type region, while the bottom layer is an N-type region. When the diode is powered by electric current, the holes in the P-type region and the electrons in the N-type region move toward the gap between the layers. There, the two charge carriers annihilate each other, releasing energy and emitting photons. This spontaneous transmission then causes further annihilation events in the junction. This creates the stimulated emission necessary to create a laser beam. The wavelength of the laser pointer depends on the semiconductor material used in the two doped layers. Early laser pointers could emit only red light with a wavelength of 633 nm. Today, laser pointers are made as diode-pumped solid-state lasers. This new and improved technology offers higher-quality laser beams and narrower spectral bandwidths. It also allows for the production of different colored laser pointers, including green, blue, and yellow.
Primer on Photonics
Published in Paul R. Prucnal, Bhavin J. Shastri, Malvin Carl Teich, Neuromorphic Photonics, 2017
Paul R. Prucnal, Bhavin J. Shastri, Malvin Carl Teich
Laser light has several important properties that are very different from thermal light. Firstly, laser radiation is spectrally pure; in other words, it has a narrow spectral linewidth. Secondly, laser radiation can exhibit very high powers. Once the laser threshold is reached, a significant portion of further pumping power will be converted to optical power at the lasing wavelength. This is different than filtered thermal light, which can have a narrow linewidth, but wastes optical power in proportion to the narrowness of the spectrum. Thirdly, laser radiation is directional, which has been experienced by anyone using a laser pointer. In the context of integrated waveguides, directionality does not apply in the same way; however, this property manifests as laser light occupying a single spatial mode. This is a very important property for many integrated devices, for example couplers, where device function relies on inputs and outputs being in a single mode.
Radiation—ionising and non-ionising
Published in Sue Reed, Dino Pisaniello, Geza Benke, Kerrie Burton, Principles of Occupational Health & Hygiene, 2020
Laser pointers are increasing in efficiency and power, with many capable of dazzling and causing an after-image if the beam enters the eye. This dazzling may have catastrophic consequences for operators of machinery. Laser pointers of power above 1 mW are prohibited imports (Australian Customs and Border Protection Service n.d.), and are controlled or prohibited as potential weapons in many jurisdictions (e.g. NSW Police Force 2009). Teachers and public speakers should keep to a class 1 or 2 laser pointer.
A holographic waveguide based eye tracking device
Published in Journal of Modern Optics, 2019
Changgeng Liu, Beatrice Pazzucconi, Juan Liu, Lei Liu, Xincheng Yao
A model eye was built to test the capability of the holographic waveguide imager to monitor eye position as shown in Figure 1(A). It was made of a 25 mm diameter ball. One segment of the ball was removed to create a 11 mm diameter flat surface. A plano-convex lens made of N-BK7 glass (refractive index 1.51, front surface curvature radius 7.7 mm and thickness 5.1 mm) was glued to this surface using optical adhesive (Norland optical adhesive 65, Thorlabs) to simulate the anterior segment of the human eye. An iris image with a 2.5 mm diameter round black spot in the centre was inserted behind the flat side of the lens to simulate the iris and the pupil. On the opposite side of the ball, coaxial with the lens, was a tube holder. A laser pointer was inserted in the holder. Its beam provided a visible backward extension of the optical axis of the model eye. This was necessary because the model eye needed to be set to known positions during prototype eye tracker evaluation. To do so, we erected a screen on the back side of the model eye, made a marker on the screen whose location intersected the backward extension of the optical axis of the model eye when it was at a desired position, and directed the laser beam to that marker (Figure 1(B)). The model eye was designed by a mechanical design software and printed by a high resolution 3D printer (Stratasys Objet30 Prime). To minimize the reflection from the flat surface of the lens, we roughened this surface using a piece of sand paper. The model eye was then mounted on a frame with two vertical supporting spherical surfaces holding the eye ball in the centre. This allowed the model eye to be rotated around its own centre as shown in Figure 1(B).
Insights into Fabrication and Measurements of PCB-Based Passive Millimeter Wave Antennas
Published in IETE Technical Review, 2021
G. S. Karthikeya, Shiban K. Koul
The antenna under test is aligned with respect to the primary beam of the horn antenna at far-field distance. Laser pointer or alignment device could be used to ensure the maximum power reception. It is highly recommended that the researcher must always make multiple measurements to optimize the alignment. The maximum power reception could be used for the rest of the measurements in other orthogonal planes or at other frequencies. The antenna under test is connected to the spectrum analyzer placed outside the anechoic chamber.
Formulation and evaluation of a two-stage targeted liposome coated with hyaluronic acid for improving lung cancer chemotherapy and overcoming multidrug resistance
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Xuelian Wang, Hongye Cai, Xinyu Huang, Zhuhang Lu, Luxi Zhang, Junjie Hu, Daizhi Tian, Jiyu Fu, Guizhi Zhang, Yan Meng, Guohua Zheng, Cong Chang
Three types of PTX-loaded liposomes were prepared using the lipid film hydration and ultrasound technique. As shown in Figure 2A, the solutions of the three liposomes were translucent with a blue opalescence, and there were no visible insoluble impurities or lumps. Upon irradiation with a laser pointer, the Tyndall effect was observed perpendicular to the direction of the laser light.