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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
If an experiment requires changing the wavelength of the optical illumination, then a tunable laser is often required. As the name suggests, a tunable laser can shift its output wavelength over a certain range. Depending on the tuning mechanism, the tuning range varies from a few nanometers to hundreds of nanometers. Wavelength tuning needs an optical dispersion assembly, such as a prism or a diffraction grating, and then selects the desired wavelength to be further amplified and output. The tuning capability is extremely useful if an experiment involves a frequency spectrum of a parameter, where only a single-laser system is needed instead of using a multitude of lasers with different wavelengths. The two most commonly used tunable lasers, categorized by their gain medium, are solid-state tunable lasers and liquid dye lasers.
Vertical External-Cavity Organic Lasers: State of the Art and Application Perspectives
Published in Marco Anni, Sandro Lattante, Organic Lasers, 2018
Sébastien Chénais, Sébastien Forget
Widely tunable laser sources in the visible part of the spectrum are required for many applications such as, for instance, spectroscopy [13,28,29] or bio-chemo sensing [30]. Liquid dye lasers have been reigning for decades over this spectral region in virtue of their unrivalled spectral coverage and wavelength agility, but they require complex and bulky flow systems and are plagued by stability and toxicity issues. Optical parametric oscillators (OPO) or generators [31,32] provide a solid-state alternative solution to get tunable visible coherent radiation, but despite many recent improvements [33], they still remain complex, cumbersome, and expensive solutions. The landscape of tunable visible sources seemed to change deeply with the advent of supercontinuum sources, which offer broadband spatially coherent light covering the visible and infrared spectrum (400–1800 nm); however, these sources have still low output spectral power densities (typ. ∼ $ \sim $ mW/nm) and are hence not ideal whenever only a specific spectral region has to be addressed, since in that case only a tiny fraction of the light is useful after filtering. Tunable visible sources based on nonlinear fibers and frequency conversion recently appeared on the marketplace but are available at a cost comparable with that of dye lasers or OPOs. In pulsed regime, OSSLs [2,3] are then appealing devices, which combine the advantages of dye lasers with those of conventional solid-state lasers, with a “low-cost” advantage.
Microring Resonators
Published in Erich Kasper, Jinzhong Yu, Silicon-Based Photonics, 2020
Figure 4.25 plots the setup for filtering measurement. The light from a frequency-tunable laser is coupled into the waveguides through a polarization controller and a polarization-maintaining fiber. The output light is collimated by a lens and then filtered by a polarizer. By turning the mirror, we can switch the collimated light either into an infrared camera or into a fiber with a collimator at the front end. With the light spot observed on the camera, we tune the measurement stages for accurate coupling. After that, the mirror is turned to lead the light to an optical spectrum analyzer (OSA) synchronously and then the transmission spectrum on the OSA is displayed.
Optical coherence tomography systems for evaluation of marginal and internal fit of ceramic reconstructions
Published in Biomaterial Investigations in Dentistry, 2022
Hiba Al-Imam, Ana R. Benetti, Pete Tomlins, Klaus Gotfredsen
Nonetheless, different types of OCT systems have been used to assess the fit of dental reconstructions since 2018 [6–10]. OCT is based on light interference between signals from a sample and a reference mirror [13–15]. Depending on the OCT system, the near infrared light can either be swept source (SS-OCT) or broadband. In the SS-OCT, a tunable laser is used to sweep the wavelengths. Broadband source is applied in the spectral domain OCT (SD-OCT) system and emits a broad range of wavelengths. In both systems, a beam splitter is used to split the light beam in two, propagating to the reference mirror and to the sample. Subsequently, the light backscattered from within the sample and from the reference mirror is coupled through the beam splitter/coupler [13–15]. In the specific SD-OCT system employed in this study, the interference fringes from the reference mirror and sample are detected using a diffraction grating and a single-line photodetector. However, other configurations may be applied in SD-OCT systems [13,15]. For the SS-OCT system, the light is detected using a single-element balanced photodetector. These interference fringes provide a single A-scan, which is a single scanned line in depth from within a sample. Raster scanning across the sample will result in propagation of A-scans, giving rise to a 2D in depth image – known as a B-scan.
A spectroscopic bandwidth correction method based on multi-bandwidth functions
Published in Journal of Modern Optics, 2022
The detail of the proposed bandwidth correction method described in this section is listed as follows: The wavelengths of the measured spectrum are divided into N segments. The bandwidth function corresponding to the central wavelength of each segment is collected by a tunable laser to construct the bandwidth function matrix .Input the values of the regularization parameter , time step , initial value , stopping conditions, and set .Calculate the estimated spectrum with Equation (15) and set .Judge whether the stopping conditions are satisfied. If not, return to step 3.Output the estimated spectrum .In this paper, the stopping conditions are set to or .
Tunable microwave photonic filters based on double-sideband modulation and linear chirped fibre Bragg gratings
Published in Journal of Modern Optics, 2021
Xiaoyun Li, Jinmei Liu, Zhixin Zou, Li Zhan
In this paper, a double-tap tunable microwave photonic filter using LCFBGs with double-side band modulation, large wavelength tunability and large dispersion filtering range have been demonstrated theoretically and experimentally. In our scheme, two LCFBGs are inserted backward into the arms of a Mach–Zehnder interferometer. By changing the optical carrier wavelength out of a tunable laser, the FSR can be varied for the microwave reflecting at different physical location of the LCFBGs. We test the tunability in the 400–500 MHz and 10–10.1 GHz frequency band within the first and the second main passband of the filter, with a large basic time difference between the two taps. The FSR of the filter can be fine-tuned in a sub-megahertz step by adjusting the optical wavelength. This scheme can be extended to multiple taps using laser arrays or more LCFBGs. We believe it may have applications in microwave processing.