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Optical Absorption and Fluorescence of Nanomaterials
Published in Vladimir I. Gavrilenko, Optics of Nanomaterials, 2019
The Rhodamine 6G (Rh6G) is a highly fluorescent rhodamine family dye. Rh6G as well as other Rhodamine family dyes are used extensively in biotechnology applications such as fluorescence microscopy, flow cytometry, fluorescence correlation spectroscopy. The Rh6G is also used as a laser dye, or gain medium, in dye lasers. It has a remarkably high photostability, high luminescence quantum yield (near 0.95), low cost, and its lasing range has close proximity to its absorption maximum. The electron energy structure of the Rh6G molecule has electron levels responsible for the singlet type optical transitions well separated on the energy scale from the backbone electronic structure. This electron energy structure of the Rh6G molecule results in a typical optical absorption and strong luminescence lines that are well separated from the optical spectra related to the excitation of the backbone electronic orbitals (Gavrilenko and Noginov, 2006).
Vibrational Spectroscopy
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Peter Fredericks, Llewellyn Rintoul, John Coates
In a dye laser a jet of dye solution is continuously cycled through an optical cavity. An Ar+ laser is used to “pump” the dye, to produce a broad-band coherent beam which is “tuned” with a suitable dispersion optic. Different laser/dye combinations may be used to provide specific wavelength ranges. With an Ar+ laser pump and a suitable selection of dyes, it is possible to cover most of the visible region. The advent of higher efficiency instruments has enabled greater use of the “red”-end lasers (HeNe NIR diode lasers) to reduce the effects of fluorescence. Dye lasers are now mainly used for special applications, such as resonance Raman where the tunability confers considerable advantage in the study of excitation profiles.
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
A dye laser uses organic dye solution as the gain medium (Figure 2.27) in both oscillator and amplifier to achieve wavelength tuning. Dye lasers are considered “passive lasers” and work with pump lasers that provide energy. A commonly used pump laser is often a high-power frequency doubled Nd:YAG laser, as shown in Figure 2.28. Like a gas laser, dye lasers use mirrors to amplify the spontaneous emission of photons within the gain medium. The mirror at the output will usually be 80% reflective, while all other mirrors are coated to be 99% reflective. This system creates the amplification needed for stimulated emission, and the 20% transmittance of the output mirror allows the laser beam to exit. Another advantage of the dye laser, besides its tuning capability, is the ability to swap the dyes. By switching the dyes in the laser, different wavelengths of light can be produced. Thus, a dye laser with a set of different dyes can output an extremely wide range of wavelengths, eliminating the need for additional lasers.
Spatially and electrically tunable random lasing based on a polymer-stabilised blue phase liquid crystal-wedged cell
Published in Liquid Crystals, 2020
Ruochen Liao, Xiyun Zhan, Xiaowan Xu, Yanjun Liu, Fei Wang, Dan Luo
The mechanism of the formation of a random laser is multiple scattering in the medium [11]. The multiple scattering not only comes from the randomly distributed BP platelets and the discontinuous boundaries, but also the index mismatch between the polymer and the refilled LC molecules. The light waves that are emitted from the laser dye travel along the BP platelets, leading to multiple scattering. Then part of the light waves goes back to the beginning position. The light experiences both loss and amplification along the closed-loop path during scattering. In that case, random lasing appears when gain is higher than loss. The scattering mean free path is a key factor for random lasers emission and influences the wavelength of the emission laser. In a scattering system, the random lasing wavelength is closely related to the scattering mean free path ls [25]. Hu et al. demonstrated that the random lasing wavelength with short ls exhibited blue-shift effect compared to that with long ls in the tunable random polymer fibre laser [26]. Herein, scattering occurs at the boundaries between BP platelets, and between general defects in the BPLC structure. As the PS-BPLC material inside the cell is compressed into thinner regions of the wedged cell, the spaces between the scattering centres will decrease. Therefore, the emitted light has a shorter dwelling time in the thin region than the thick region, which leads to the reduction of the value of the scattering mean free path ls and the blue-shifted laser emission.
Low threshold polymerised cholesteric liquid crystal film lasers with red, green and blue colour
Published in Liquid Crystals, 2019
Xiyun Zhan, Huiping Fan, Yong Li, Yanjun Liu, Dan Luo
The central wavelength λc of reflection band of CLC is determined by the equation: λc = navp, where nav is the average refractive index and p is the pitch of helical structure. The bandwidth Δλ of reflection is given by Δλ = (ne − no) × p, where ne and no is the ordinary and extraordinary refractive index of NLC, respectively. Three mixtures with different concentrations of NLC and chiral dopant that correspond to different reflection band for RGB lasers generation are shown in Table 1. The NLC and chiral dopant were mixed with RMs (25 wt%) and photo-initiator Darocur1173 (1 wt%) thoroughly to achieve PCLC film. During mixing process, the mixtures were heated up to 70°C in isotropic phase of NLC and stirred at about 1000 rpm with the help of the magnetic stirrer for 10 min. The refilled materials include laser dye of DCM or C540A and NLC.
On the Basic Extraction Properties of a Phenyl Trifluoromethyl Sulfone-Based GANEX System Containing CyMe4-BTBP and TBP
Published in Solvent Extraction and Ion Exchange, 2018
Jenny Halleröd, Christian Ekberg, Thea Authen, Laura Bertolo, Mu Lin, Bohumír Grüner, Jaroslav Švehla, Christoph Wagner, Andreas Geist, Petra Panak, Emma Aneheim
During the Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) measurements, Cm(III) (10 M) was extracted from 4 M HNO3 into organic phases composed of 10 mM CyMe4-BTBP in (a) 100% FS-13 or (b) 70% FS-13 and 30% TBP. Phase contacting time was 1 h or 4 h. The separated organic phase was transferred into a quartz cuvette (1 cm path length) and measured (T = 25°C). TRLFS studies were performed using a Nd:YAG laser-pumped (Continuum Surelite Laser) dye laser system (NARROWscan D-R Dye Laser) with a repetition rate of 10 Hz. Cm(III) was excited using a wavelength of = 396.6 nm. Following spectral decomposition by a spectrograph (Shamrock 303i, 1199 lines mm), the spectra were recorded by an Intensified Charge-Coupled Devices (ICCD) camera (iStar Gen III, ANDOR) with an integrated delay controller. The fluorescence signal was detected after a delay time of 1 s to discriminate scattering light and short-lived fluorescence of organic compounds.