We have realized phase encoding and sensing of signals for quantum cryptography in compact circuits made with
standard silica-on-silicon technology. The circuits include Bragg grating filters allowing multichannel cryptography with
dense channel spacing, and they are thermally balanced to avoid crosstalk.
The development of new techniques for writing and tailoring the properties of Bragg gratings has generated a suite of
distinct grating types that are optimised for performance within different temperature windows. These cover gratings
produced by recipes such as hypersensitisation, thermal processing and single and multiphoton writing. In this paper, we
review four types of high temperature gratings that offer comprehensive coverage of temperature space for most
applications of interest. Up to 1200°C novel processing methods allow standard silica-based optical fibres to be used.
However, beyond these temperatures, optical fibres made from other materials, such as sapphire, need consideration.
We report some of our recent progress in the area of Bragg grating writing in photonic crystal fibres (PCFs). The various
challenges that PCFs present are discussed and the methods used to overcome these challenges are presented. The
fabrication of highly-durable type-IIa gratings in highly nonlinear photonic crystal fibre is demonstrated, the rotational
variance of grating inscription is also investigated through both experiments and numerical modeling. In other
experiments we fabricate a narrow-linewidth distributed feedback (DFB) laser in erbium-doped PCF, achieving stable,
single-mode and CW operation. The potential of such a DFB PCF in sensing applications is assessed by accurately
measuring an absorption line of acetylene gas.
The measurement of the tuning speed in fiber Bragg gratings is an increasingly important parameter for characterizing the dynamics of
tunable devices. Optical spectrum analyzers and wavelength meters are not suitable due to their slow response for measuring the
wavelength shift in time. In this paper we report on a technique for estimating the tuning speed of a fiber Bragg grating which is based
on accessing the wavelength shift through a calibration curve and measuring the time in which the shift occurs with the help of a fast
photo-detector.
A distributed feedback laser was fabricated in Er3+-doped photonic crystal fibre. Single mode lasing is obtained with
<10kHz linewidth. The output was amplified to 12mW using a commercial erbium doped fibre amplifier (EDFA).
A well-known side-effect from fibre Bragg grating UV-fabrication is short wavelength attenuation, where irradiation
with laser light, usually in the UV, generates both defect-induced absorption and scattering. These losses are especially
problematic for high power optical fibre lasers operating at shorter wavelengths where resonant assisted coupling into the
glass matrix through the rare earth ions can take place (e.g. Yb3+). In this, work we present a study of the relative
magnitude of short wavelength attenuation in gratings written by the point-by-point method using a Ti-sapphire
femtosecond laser operating at 800 nm. Such gratings are very stable and have been used as the feedback elements in
fibre lasers with powers exceeding 100 W. We show that the scattering properties responsible for the attenuation are
analogous to those associated with type II gratings written with UV lasers.
The construction and operation of a DFB photonic crystal fibre laser produced in Er3+ core doped air-silica structured optical fibre is presented. Its potential in sensing generally is elaborated.
A Bragg grating in a two-mode air-silica structured PCF was written and its dependence with temperature and strain analyzed. The temperature and strain calibration curves for both modes are measured and found to be distinct.
Type IIA fibre Bragg gratings were produced in pristine boron-codoped germanosilicate optical fibre that were shown to have remarkable high-temperature resistance. The temperature resistance and decay behaviour of these gratings is presented.
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