One- and two-dimensional forms of carbon, carbon nanotube, and graphene, and related 2D
materials, have attracted great attention of researchers in many fields for their
interesting and useful ...electrical, optical, chemical, and mechanical properties. In this
tutorial, we will introduce the basic physics and the linear optical properties of these
1D/2D materials. We then focus on their nonlinear optical properties, saturable
absorption, electro-optic effect, and nonlinear Kerr effect. We will also review and
discuss a few key applications using the ultrafast nonlinear phenomena possessed by these
1D/2D materials: (1) short-pulse fiber lasers using saturable absorption, (2)
electro-optic modulators, and (3) all-optical signal processing devices.
One and two dimensional forms of carbon, Carbon nanotube and graphene, have interesting and useful not only electronic but also photonic properties. This tutorial will review their photonic ...properties, linear and nonlinear, and applications of nonlinear photonic properties as laser mode lockers and nonlinear functional devices.
Swept-source optical coherence tomography (SS-OCT) is a powerful tool for fast medical imaging. For the real-time three-dimensional imaging, the wide tuning range over 100 nm and fast sweep rate over ...100 kHz are typically required. We have proposed a new wavelength-swept laser for SS-OCT. It is based on a principle called dispersion tuning. Since the cavity contains no mechanical components, such as tunable filters, we could achieve the very high sweep rate. In this paper, we describe the principle of the dispersion-tuned swept laser and present our recent works on the applications to the SS-OCT system.
There is an increasing demand for all-fiber passively mode-locked lasers with pulse repetition rates in the order of gigahertz for their potential applications in fields such as telecommunications ...and metrology. However, conventional mode-locked fiber lasers typically operate at fundamental repetition rates of only a few megahertz. In this paper, we report all-fiber laser operation with fundamental repetition rates of 4.24 GHz, 9.63 GHz and 19.45 GHz. This is, to date and to the best of our knowledge, the highest fundamental repetition rate reported for an all-fiber laser. The laser operation is based on the passive modelocking of a miniature all-fiber Fabry-Pérot laser (FFPL) by a carbon nanotube (CNT) saturable absorber. The key components for such device are a very high-gain Er:Yb phosphosilicate fiber and a fiber compatible saturable absorber with very small foot print and very low losses. The laser output of the three lasers was close to transform-limited with a pulsewidth of approximately 1 ps and low noise. As a demonstration of potential future applications for this laser, we also demonstrated supercontinuum generation with a longitudinal mode-spacing of 0.08 nm by launching the laser operating at 9.63 GHz into 30 m of a highly nonlinear dispersion shifted fiber.
Optical devices based on carbon nanotubes (CNTs) have been realized with several fabrication methods in different structures, such as free-space, fiber-end, waveguide, and fiber structures. Most of ...waveguide- and fiber-type devices utilize evanescent coupling between the guided light and CNT layers, and offer very high optical damage threshold and high third-order nonlinearity. However, the conventional fabrication methods require complicated processes and waste much of CNTs. In this work, we propose and demonstrate CNT deposition around microfibers induced by injecting light through the fibers. This method can area-selectively deposit desired number of CNTs around microfibers, and can be realized by a simple process and setup. We also demonstrate a passively mode-locked fiber laser using a CNT-deposited microfiber as a passive mode-locker.
Mode-locked fiber lasers are currently undergoing a significant evolution towards higher pulse energies and shorter pulse durations. A key enabler in this progress has been the discovery of novel ...saturable absorbers (SA) such as carbon nanotubes (CNT) and graphene. The exceptional properties of CNTs as SA have been extensively studied in recent years. Graphene, a one atom thick planar sheet of carbon atoms arranged into a hexagonal lattice, has been recently proposed as an alternative to CNTs in several photonics applications. Here, we propose a method for the integration of graphene into a fiber ferrule using an optical deposition technique, which has been also employed for the deposition of CNT directly on the core of a fiber edge and in tapered fibers. We investigate and compare the optical properties of CNT-SA and graphene-SA fabricated by this optical deposition technique. Soliton-like, mode-locked lasing is confirmed using an erbium doped optical fiber in an all-fiber ring cavity laser configuration.
We present a high-speed wavelength-swept fiber laser based on a dispersion tuning method using a reflective semiconductor optical amplifier (RSOA) and a chirped fiber Bragg grating (CFBG). By using ...these devices, the cavity length can be shortened drastically. The short cavity improves the laser performance at high sweep rates over 200 kHz. We achieve a sweep range of 60 nm and an output power of 8.4 mW at 100 kHz sweep. We applied the dispersion-tuned fiber laser to the swept-source OCT system and successfully obtained OCT images of an adhesive tape at up to 250 kHz sweep rate.
We demonstrate for the first time a strain-controlled all polarization-maintaining (PM) fiber Lyot filter based on a piezoelectric lead zirconate titanate (PZT) fiber stretcher. This filter is ...implemented in an all-PM mode-locked fiber laser to serve as a novel wavelength-tuning mechanism for fast wavelength sweeping. The center wavelength of the output laser can be tuned across a range from 1540 nm to 1567 nm linearly. And the strain sensitivity achieved in the proposed all-PM fiber Lyot filter is 0.052nm/με, which is 43 times higher than that achievable by other strain-controlled filters such as a fiber Bragg grating filter (0.0012nm/με). Wavelength-swept rates up to 500 Hz and wavelength tuning speeds up to 13,000 nm/s are demonstrated, which is hundreds of times faster than what is attainable with conventional sub-picosecond mode-locked lasers based on mechanical tuning methods. This highly repeatable and swift wavelength-tunable all-PM fiber mode-locked laser is a promising source for applications requiring fast wavelength tunability, such as coherent Raman microscopy.
In this paper, we propose a new way of estimating the absorption in graphene coated silicon wire waveguides based on a self-developed, modified 2D Finite Difference Method, and use it to obtain a ...detailed absorption dependency of the waveguide design. For the first time, we observe peaks in the TM mode absorption curves, as well as the reversals of the dominantly absorbed mode with waveguide design variation, both of which have not been predicted previously theoretically, but have been implied through experimental results. We also provide a qualitative explanation of our novel numerical results, and explain how these results can be utilized in optimization of various graphene based integrated devices like optical modulators, photodetectors and optical polarizers.
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