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US 5,830,622 AGranted
Optical grating
AssigneeThe University of Sydney
InventorsJohn Canning, Mark Sceats
Life of this patent
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Abstract
An optical grating is formed by exposing linearly spaced regions of an optical fibre (10), typically a germanosilicate core fibre, to UV irradiation to produce spaced apart regions (12 and 13) of differing refractive index within the core (11) of the fibre. The grating characteristics are modified to create a relatively complex structure, for example a pi- shifted distributed phase structure, by post-processing the grating. This is achieved by exposing at least one concomitant region (14) of the grating to localised UV irradiation.
Claims21
A method of forming an optical grating which comprises the steps of:
- (a) forming a first grating structure by exposing substantially equally linearly spaced regions of a glass light transmitting device to optical irradiation, the regions being spaced apart in the direction of intended light propagation through the device, said optical irradiation having an intensity, dose level and wavelength appropriate to cause a localised increase in the refractive index of the device in said exposed regions;
- and
- (b) either prior to or following exposure of the linearly spaced regions, individually exposing a concomitant region or contiguous group of concomitant regions of the grating structure to optical irradiation localised only to said concomitant region or said contiguous group of regions, the optical irradiation having a substantially uniform magnitude across said concomitant region(s) and having an intensity, dose level and wavelength appropriate to cause a localised increase in the refractive index of the device substantially only in said concomitant region or group of regions so as to divide said grating structure into at least two smaller grating structures separated by said concomitant region(s).
Dependencies are inferred from the claim text.