Compact birefringent waveplates photo-induced in silica by femtosecond laser

© 2014 by the authors; licensee MDPI, Basel, Switzerland. Recently, we showed that femtosecond laser induced "nanogratings" consist of thin regions with a low refractive index (Δn = -0.15), due to the formation of nanoporous silica surrounded by regions with a positive index change. In this paper, we investigate a wide range of laser parameters to achieve very high retardance within a single layer; as much as 350 nm at λ = 546 nm but also to minimize the competing losses. We show that the total retardance depends on the number of layers present and can be accumulated in the direction of laser propagation to values higher than 1600 nm. This opens the door to using these nanostructures as refined building blocks for novel optical elements based on strong retardance

Embedded nanograting-based waveplates for polarization control in integrated photonic circuits

Femtosecond laser direct writing (FLDW) enables precise three-dimensional structuring of transparent host materials such as fused silica. With this technique, reliable integrated optical circuits can be written, which are also a possible candidate for future quantum technologies. We demonstrate the manufacturing of integrated waveplates with arbitrary orientations and various phase delays by combining embedded birefringent nanograting structures and FLDW waveguides in fused silica glass. These waveplates can be used both for classical applications and for quantum gates

Mode-locking of thulium-doped and Erbium-doped fiber lasers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 140-152).by Lynn Elizabeth Nelson.Ph.D

The ultrafast laser inscription of photonic devices for integrated optical applications

A study of some key areas in which ultrafast laser inscription may usefully be employed is presented. The thesis includes waveguide inscription in a variety of substrates including passive glass, doped glass and a nonlinear crystal. The work contained can be split into three studies, with some overlap between them. Firstly fused silica glass is used, both in planar substrates and as flat fibre, for the inscription of two sensing elements. The planar substrate is used for a device similar in design to a side-polished fibre and the flat fibre is used for the fabrication of a Bragg grating waveguide array. In the second study, waveguides are inscribed in the nonlinear crystal monoclinic bismuth borate, and used for guided mode second harmonic generation. A novel waveguide design is employed to increase overlap between the pump and second harmonic waveguide modes. The remainder of the thesis investigates the applicability of ultrafast laser inscription to the fabrication of compact modelocked lasers. Lasing is demonstrated, both continuous wave and modelocked, using a laser inscribed erbium doped bismuthate glass waveguide as the gain element. A study is then undertaken into methods of integrating carbon nanotubes, used as saturable absorbers to modelock lasers, into laser inscribed waveguides

All-Fiber Mode-Locked Ultrafast Thulium-Doped Fiber Lasers at 2um

In this work, we demonstrate three original all-fiber ring configurations of passively modelocked Thulium-doped fiber(TDF) lasers operated around 2μm wavelength for which the usage of free-space optics components is minimized. Different mode-locking techniques/materials e.g. nonlinear polarization evolution (NPE), graphene-based saturable asbsorbers(GSAs) and single-wall carbon nanotubes (SWCNTs) are developed and used to passively mode lock TDF laser and produce ultrashort pulses at 2μm. Also to achieve higher pulse energy directly from a fiber oscillator, the net intra-cavity dispersion is managed by the introducing of normal dispersion fiber(NDF) at 2μm into the fiber cavity. Both the sign and amount of the net cavity dispersion can be controlled without compromising the merits of all-fiber configuration. Distinctive ultrashort pulses of different pulse shapes and per-pulse energies e.g. solitons, noise-like pulses and dissipative solitons are produced from these fiber lasers for which the generated pulses’ features and dynamics are experimentally investigated and characterized. A computational model is built to simulate these mode-locked TDF lasers by numerically solving the Nonlinear Schr˝odinger Equations(NLSE)