Method of making a waveguide and a waveguide made thereby

Abstract

A method of making a waveguide, the method including depositing discrete units of optical core material in a pattern of the waveguide, and controlling the refractive index of the discrete units such that the refractive index of the waveguide varies along its length.

1 . A method of making a waveguide, the method comprising:
 depositing discrete units of optical core material in a pattern of the waveguide; and selecting the refractive index of the discrete units such that the refractive index of the waveguide varies along its length.   
     
     
         2 . A method according to  claim 1 , in which the step of controlling the refractive index of the discrete units comprises mixing two or more components of optical core material of different refractive index to produce a discrete unit of optical core material having a refractive index dependent on the refractive indices of the components and/or the proportions in which they are mixed. 
     
     
         3 . A method according to  claim 1 , in which the discrete units of optical core material are liquid droplets of optical polymer material. 
     
     
         4 . A method according to  claim 3 , in which the deposited discrete units of optical core material are left for a period of time prior to hardening so as to allow diffusion between discrete units to smooth out refractive index differences at the boundaries of the discrete units. 
     
     
         5 . A method according to  claim 3 , comprising after the droplets have been deposited, curing the droplets with curing radiation. 
     
     
         6 . A method according to  claim 1 , comprising:
 providing a first source of a first optical material having a relatively high refractive index and a second source of a second optical material having a relatively low refractive index.   
     
     
         7 . A method according to  claim 6 , comprising varying the proportion of discrete units of the first type with respect to the number of the second type deposited along the waveguide thereby to control variation in the refractive index of the waveguide along its length. 
     
     
         8 . A method according to  claim 1 , in which the average diameter of each discrete unit is at least an order of magnitude less than the width of the waveguide. 
     
     
         9 . A method according to  claim 1 , comprising forming the waveguide on an optical cladding layer and providing an upper cladding on top of the waveguide once formed. 
     
     
         10 . A method according to  claim 1 , in which the waveguide is a tapered waveguide having a tapered optical core and an optical cladding around the core, in which the refractive index difference between the cladding and the core material increases from a relatively thick end of the waveguide to a relatively narrow end. 
     
     
         11 . A method according to  claim 6 , comprising mixing the desired proportions of the first and second type of optical core material in a conduit between the source and the point of application to achieve a desired refractive index for each of the dispensed units. 
     
     
         12 . A method according to  claim 6 , comprising, providing plural dispensers each containing a polymer with a refractive index different to all the others, the method comprising providing one or more discrete units from each of the dispensers to achieve a waveguide with a refractive index that varies along its length. 
     
     
         13 . An apparatus for forming an optical waveguide, the apparatus comprising:
 a nozzle for dispensing discrete units of optical material from two or more sources of optical material of different refractive index; and   a controller configured to control the nozzle to deposit discrete units of optical core material in a pattern of the waveguide, and to control the refractive index of the discrete units such that the refractive index of the waveguide varies along its length.   
     
     
         14 . An apparatus according to  claim 13 , comprising a conduit for mixing optical material from the two or more sources to obtain a resultant material of desired refractive index for deposition to form the waveguide. 
     
     
         15 . An apparatus according to  claim 14 , in which the nozzle is sized to produce discrete units of optical material having a width at least an order of magnitude smaller than the width of the waveguide being formed. 
     
     
         16 . An apparatus according to  claim 14 , in which there are only two sources of optical material of different refractive index, the refractive index of the material from one of the sources being higher than that of the other,
 wherein the controller is arranged to control the nozzle to dispense discrete units from each of the two sources in a desired proportion so as to achieve a desired variation in refractive index along the waveguide.   
     
     
         17 . An apparatus according to  claim 13 , in which there are plural sources of optical material each for containing optical material with a different refractive index. 
     
     
         18 . An apparatus according to  claim 13 , comprising a radiation source arranged to irradiate the optical material before, during or after it has been dispersed from the or each nozzle. 
     
     
         19 . An apparatus for forming an optical waveguide, the apparatus comprising:
 a nozzle for dispensing of optical material from two or more sources of optical material of different refractive index;   a conduit for mixing optical material from the two or more sources to obtain a resultant material of desired refractive index for deposition to form the waveguide; and   a controller configured to control the apparatus to deposit a continuous stream of optical material and to vary the composition of the stream during dispensing so as to determine variation in the refractive index of the waveguide as it is formed.   
     
     
         20 . An apparatus according to  claim 19 , comprising a curing radiation source for irradiating the stream before, during or after it has been dispensed from the nozzle to at least partially cure the material before it is deposited on a substrate. 
     
     
         21 .- 28 . (canceled)