Dynamics of thermal annealing of fiber gratings directly written by an infrared femtosecond laser

The inscription of fibre Bragg gratings using infrared femtosecond laser offers a number of advantages over conventional methods based on UV inscription. The refractive index modification in femtosecond inscription is independent on defect formation and therefore should not experiment the defect-related thermal decay of UV inscribed gratings. In this paper, the response to thermal annealing of fiber Bragg gratings inscribed using a tightly focussed femtosecond laser is investigated. Experimental results reveal a vastly improve thermal stability compared to gratings inscribed using conventional methods based on UV light. Erasure was not observed until temperatures in the range between 900°C and 1000°. These devices are therefore particularly suited to work in hostile environments and as high temperature sensors

Bidirectional nonreciprocal wavelength-interleaving coherent fiber transversal filter

A bidirectional nonreciprocal wavelength-interleaving filter based on an optically coherent high birefringence fiber transversal filter structure is demonstrated. Stable, low loss, low dispersion, and high isolation operation is demonstrated with reconfigurable transfer characteristics for interleaved channel spacing of 0.8 nm

Microchannels in conventional single-mode fibers

Microchannels are fabricated into conventional single-mode fibers by femtosecond laser processing and chemical etching. Fabrication limitations imposed by the fiber geometry are highlighted and resolved through a simple technique without compromising fabrication flexibility. A microfluidic fiber device consisting of a 4 μm wide microchannel that intersects the fiber core for refractive index sensing is further demonstrated. © 2006 Optical Society of America

Investigation of ultrafast laser photonic material interactions: challenges for directly written glass photonics

Currently, direct-write waveguide fabrication is probably the most widely studied application of femtosecond laser micromachining in transparent dielectrics. Devices such as buried waveguides, power splitters, couplers, gratings and optical amplifiers have all been demonstrated. Waveguide properties depend critically on the sample material properties and writing laser characteristics. In this paper we discuss the challenges facing researchers using the femtosecond laser direct-write technique with specific emphasis being placed on the suitability of fused silica and phosphate glass as device hosts for different applications.Comment: 11 pages, 87 references, 11 figures. Article in revie

Waveguide laser formed in YAG: Nd3+ crystal by femtosecond laser inscription

A technique of direct writing of depressed cladding waveguides by a tightly focused, femtosecond laser beam in laser crystals has been developed. A laser based on a depressed cladding waveguide in a Neodimium doped YAG crystal has been demonstrated for the first time

Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

The properties of fiber Bragg gratings in hydrogenated fibers under conditions of ultraviolet overexposure were investigated. Abnormal spectral evolution of the regenerated grating following erasure of the initial type I grating was observed in the hydrogenated fibers. The regenerated grating also exhibited less temperature sensitivity and an 18 nm shift in the Bragg wavelength

Point-by-point inscription of first-order fiber Bragg grating for C-band applications

The influence of the fiber geometry on the point-by-point inscription of fiber Bragg gratings using a femtosecond laser is highlighted. Fiber Bragg gratings with high spectral quality and strong first-order Bragg resonances within the C-band are achieved by optimizing the inscription process. Large birefringence (1.2x10-4) and high degree of polarizationdependent index modulation are observed in these gratings. Potential applications of these gratings in resonators are further illustrated. © 2007 Optical Society of America

Fabrication of high-rejection, low-loss filters by the concatenation of broadly chirped fibre Bragg gratings

Single- and multiple-bandpass filters with broad, high- rejection stopbands and narrow, low-loss passbands are significant components for fiber networks. Hitherto, this combination of characteristics has proved elusive using in- fiber grating techniques. Here, we report the realization of practical single-passband filters synthesized from concatenated chirped broadband fiber gratings written holographically in a highly photosensitive fiber. Practical, low-loss (< 2 dB), single-passband fiber Bragg grating transmission filters have been fabricated with greater than 30 dB out-of-band rejection over a 25 nm spectral width. ©2005 Copyright SPIE - The International Society for Optical Engineering

Bandpass switching in a nonlinear optical loop mirror

A novel device configuration is used to demonstrate wavelength-confined, a bandpass, switching in a nonlinear-optical loop mirror (WOLM). Demonstrated is a self-switching in the soliton regime using a partially reflecting Bragg grating as a wavelength-dependent loss element. Two wavelength operation in which a signal is switched through the use of cross phase modulation, are demonstrated. Observed is the operation of the device confined to wavelengths defined by the grating reflection band

Advances in fiber grating technology for sensor applications

Sensing techniques employing UV-inscribed fibre Bragg gratings and long period fibre gratings continue to make significant advances. A number of recently established concepts are described offering improved sensor performance, multiplex capacity, and simplicity, and results from new application areas presented