Active Fibre Mode-locked Lasers in Synchronization for STED Microscopy
01 Jan 2019-pp 233-253
TL;DR: In this paper, the authors investigate the characteristics of an actively mode-locked ring laser, designed as a slave laser and driven by a commercial Ti:Sapphire laser acting as a master.
Abstract: Mode-locked fibre ring lasers can generate picosecond optical pulse widths with MHz repetition rates. Applications in optical imaging, or in experiments with pump-probe lasers, benefit from being able synchronize two lasers at high repetition rates, while retaining the narrow optical pulse widths. We investigate the characteristics of an actively mode-locked fibre ring laser, designed as a slave laser and driven by a commercial Ti:Sapphire laser acting as a master. The master-slave synchronization was stabilized for frequency detuning by matching the cavity lengths, and the dependence of the output pulse width of the slave laser was studied as its cavity was detuned. The increase in pulse width was asymmetric about the ring cavity resonance frequency, a phenomenon that we were able to establish as a consequence of an asymmetry in the detuning range of the higher order cavity modes. We observed that the detuning range decreased linearly with the mode number, an observation that was supported by a theoretical perturbative analysis of cavity locking.
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TL;DR: In this article , multiple RF inputs are shown, theoretically, to relock and extend the locking range of cavity modes in a detuned partially mode-locked fiber ring laser (AMLL).
Abstract: Actively mode-locked fiber ring lasers (AMLLs) with loss modulators are used to generate approximately 100ps pulses with 100MHz repetition. RF detuning around the fundamental frequency, f0, causes a loss in phase lock (unlocking) of cavity modes and partial mode locking. Multiple RF inputs are shown, theoretically, to relock and extend the locking range of cavity modes in a detuned partially mode-locked AMLL. A custom-built Yb3+-doped AMLL with f0=26MHz, and operating wavelength of 1064nm, was used to experimentally verify the theoretical predictions. Two RF sinusoidal signals with constant phase and equal amplitude resulted in an extension of the range by Xn=6.4kHz in addition to the range Rn=14.34kHz with single input for the mode n=10. An increase in locking range was also observed for higher modes. Pulsewidth reduction to approximately 205ps from about 2ns was also observed in the AMLL.
TL;DR: In this paper , the authors present a review of three advanced microscopy techniques, i.e., microspectrophotometry (MSP), super-resolution localization microscopy (SRLM), and holotomographic microscopy(HTM), which can achieve an insight view into the role intracellular molecular organizations such as photoreceptive and photosynthetic structures and lipid bodies play in many cellular processes as well as their biophysical properties.
Abstract: Though microscopy is most often intended as a technique for providing qualitative assessment of cellular and subcellular properties, when coupled with other instruments such as wavelength selectors, lasers, photoelectric devices and computers, it can perform a wide variety of quantitative measurements, which are demanding in establishing relationships between the properties and structures of biological material in all their spatial and temporal complexities. These combinations of instruments are a powerful approach to improve non-destructive investigations of cellular and subcellular properties (both physical and chemical) at a macromolecular scale resolution. Since many subcellular compartments in living cells are characterized by structurally organized molecules, this review deals with three advanced microscopy techniques well-suited for these kind of investigations, i.e., microspectrophotometry (MSP), super-resolution localization microscopy (SRLM) and holotomographic microscopy (HTM). These techniques can achieve an insight view into the role intracellular molecular organizations such as photoreceptive and photosynthetic structures and lipid bodies play in many cellular processes as well as their biophysical properties. Microspectrophotometry uses a set-up based on the combination of a wide-field microscope and a polychromator, which allows the measurement of spectroscopic features such as absorption spectra. Super resolution localization microscopy combines dedicated optics and sophisticated software algorithms to overcome the diffraction limit of light and allow the visualization of subcellular structures and dynamics in greater detail with respect to conventional optical microscopy. Holotomographic microscopy combines holography and tomography techniques into a single microscopy set-up, and allows 3D reconstruction by means of the phase separation of biomolecule condensates. This review is organized in sections, which for each technique describe some general aspects, a peculiar theoretical aspect, a specific experimental configuration and examples of applications (fish and algae photoreceptors, single labeled proteins and endocellular aggregates of lipids).
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TL;DR: The authors' simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver, which resolves objects only a few nanometers across.
Abstract: Optical lenses have for centuries been one of scientists’ prime tools. Their operation is well understood on the basis of classical optics: curved surfaces focus light by virtue of the refractive index contrast. Equally their limitations are dictated by wave optics: no lens can focus light onto an area smaller than a square wavelength. What is there new to say other than to polish the lens more perfectly and to invent slightly better dielectrics? In this Letter I want to challenge the traditional limitation on lens performance and propose a class of “superlenses,” and to suggest a practical scheme for implementing such a lens. Let us look more closely at the reasons for limitation in performance. Consider an infinitesimal dipole of frequency v in front of a lens. The electric component of the field will be given by some 2D Fourier expansion,
10,974 citations
TL;DR: The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation.
Abstract: Molecular excitation by the simultaneous absorption of two photons provides intrinsic three-dimensional resolution in laser scanning fluorescence microscopy. The excitation of fluorophores having single-photon absorption in the ultraviolet with a stream of strongly focused subpicosecond pulses of red laser light has made possible fluorescence images of living cells and other microscopic objects. The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation. This technique also provides unprecedented capabilities for three-dimensional, spatially resolved photochemistry, particularly photolytic release of caged effector molecules.
8,905 citations
TL;DR: A new type of scanning fluorescence microscope capable of resolving 35 nm in the far field is proposed, overcome the diffraction resolution limit by employing stimulated emission to inhibit the fluorescence process in the outer regions of the excitation point-spread function.
Abstract: We propose a new type of scanning fluorescence microscope capable of resolving 35 nm in the far field. We overcome the diffraction resolution limit by employing stimulated emission to inhibit the fluorescence process in the outer regions of the excitation point-spread function. In contrast to near-field scanning optical microscopy, this method can produce three-dimensional images of translucent specimens.
5,110 citations
IBM1
TL;DR: In this paper, surface microscopy using vacuum tunneling has been demonstrated for the first time, and topographic pictures of surfaces on an atomic scale have been obtained for CaIrSn 4 and Au.
Abstract: Surface microscopy using vacuum tunneling is demonstrated for the first time. Topographic pictures of surfaces on an atomic scale have been obtained. Examples of resolved monoatomic steps and surface reconstructions are shown for (110) surfaces of CaIrSn 4 and Au.
4,290 citations
Journal Article•
TL;DR: In this paper, the authors proposed a new type of scanning fluorescence microscope capable of resolving 35 nm in the far field by employing stimulated emission to inhibit the fluorescence process in the outer regions of the excitation point spread function.
Abstract: We propose a new type of scanning fluorescence microscope capable of resolving 35 nm in the far field. We overcome the diffraction resolution limit by employing stimulated emission to inhibit the fluorescence process in the outer regions of the excitation point-spread function. In contrast to near-field scanning optical microscopy, this method can produce three-dimensional images of translucent specimens.
3,987 citations