Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/02—Optical fibres with cladding with or without a coating
  • G02B6/02295—Microstructured optical fibre
  • G02B6/023—Microstructured optical fibre having different index layers arranged around the core for guiding light by reflection, i.e. 1D crystal, e.g. omniguide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B6/122—Basic optical elements, e.g. light-guiding paths
  • G02B6/1225—Basic optical elements, e.g. light-guiding paths comprising photonic band-gap structures or photonic lattices
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B6/122—Basic optical elements, e.g. light-guiding paths
  • G02B6/124—Geodesic lenses or integrated gratings
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B2006/12083—Constructional arrangements
  • G02B2006/12107—Grating
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
  • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
  • G02B2006/12083—Constructional arrangements
  • G02B2006/12119—Bend

Definitions

• the present invention relates broadly to an optical device comprising a waveguide and a process for fabricating the same.
• the directing of light signals m different directions would also be desirable m devices where it is required to confine light to a predetermined path within the waveguide, for example m optical filter or optical resonator structures.
• the present invention provides an optical device comprising a waveguide structure, at least one grating structure formed m the waveguide structure; the grating structure being disposed to direct along a selected path m the waveguide structure light of a predetermined wavelength entering the waveguide structure at a predetermined angle of incidence to the grating structure.
• the waveguide structure may be formed from photosensitive material, and the grating structure may be formed by UV-mduced refractive index variations m the waveguide.
• the present invention allows for angular dispersion to be added to a propagating light signal which can be controlled by the properties of the grating structures. This can be utilised for e.g. dispersion compensation, pulse shirpmg, or pulse compressing. This is because different wavelengths see a different angular path with respect to the grating structure.
• the device may be utilised m complex light manipulation circuits both m the spectral and time domain.
• the grating structure may comprise a chirped grating.
• the grating structure may be disposed to direct the light m a reflection or m a transmission mode.
• the present invention may alternatively be defined as providing an optical device comprising a waveguide of photosensitive material; at least one grating structure formed by UV-mduced refractive index variations m the waveguide; the grating structure being disposed to confine to a selected path m the waveguide light of a predetermined wavelength entering the waveguide at a predetermined angle of incidence to the grating structure. Because of the angular dependence of the accepted wavelength m the grating confined waveguide such devices can e.g. depend on angular sweep to isolate wavelengths or signals .
• the grating structure may comprise a contmuos grating. Alternatively, the grating structure may comprise two gratings which mirror each other.
• the grating structure comprises regions of constant refractive index which extent m the propagation direction of the waveguide.
• the regions may extend parallel to the propagation direction .
• the regions may extend cylmdrically parallel to the propagation direction.
• the regions may extend elipsoidically parallel to the propagation direction.
• the device may further comprise at least one optical reflector disposed m a direction transverse to the propagation direction to aid m confining the light to the path .
• the device may comprise two or more grating structures angularly disposed with respect to each other to channel the light around the selected path. Accordingly, different confinement conditions may be realised at different boundaries of the waveguide.
• the grating structures may be formed by UV-holography .
• the gratings may be chirped gratings.
• the gratings may be sampled gratings.
• the device may be a filter, a resonator, or a sensor.
• the device is a sensor further comprising means for measuring an intensity of the light at a predetermined point along the selected path for determining changes m the intensity due to induced changes m confinement conditions of the sensor.
• the changes may be induced by gas molecules entering the waveguide.
• the present invention may alternatively be defined as providing a process for fabricating an optical device comprising a waveguide of photosensitive material, the method comprising the step of forming at least one grating structure by UV-mduced refractive index variations m the waveguide; the grating structure being disposed to confine to a selected path m the waveguide light of a predetermined wavelength entering the waveguide at a predetermined angle of incidence to the grating structure.
• Figure 1 is a schematic drawing of a device embodying the present invention.
• Figure 2 is a schematic drawing of a device embodying the present invention.
• Figure 3 is a schematic drawing of a device embodying the present invention.
• Figure 4 is a schematic drawing of a device embodying the present invention.
• Figure 5 is a schematic drawing of a device embodying the present invention.
• Figure 6 illustrates m an isometric view a method of fabricating a grating confined waveguide embodying the present invention.
• Figure 7 illustrates m an isometric view another method of fabricating a grating confined waveguide embodying the present invention.
• Figure 8 is a schematic drawing m a cross-sectional view illustrating a device embodying the present invention.
• Figure 9 is shows a plot of resonant angle against grating period for a grating confined waveguide.
• Figure 10 is a schematic drawing m an isometric view illustrating a device embodying the present invention.
• Figure 11 is a schematic drawing m a top view illustrating a device embodying the present invention.
• Figure 12 is a schematic drawing m a cross-sectional side view illustrating a device embodying the present inventio .
• Figure 13 is a schematic drawing m an isometric view of a resonator structure embodying the present invention.
• Figure 14 is a schematic drawing m an isometric view of a device embodying the present invention. Detailed Description of the Preferred Embodiments
• a grating structure 4 is written in the vicinity of the tight bend.
• the grating structure 4 effectively has a photonic band gap preventing the effervescent light 2 from leaking out and resulting m higher efficiency m the light coupled to output 5. This results m a substantial reduction m the bending loss as a result of the utilization of the detraction grating 4 which m turn allows for tighter bends to be formed m the waveguide structure.
• the wavelength of the grating 4 can be tuned so as to match desired frequencies for operation.
• the grating 6 can be written m a reflection mode so as to provide for reflection of desired frequencies along the path 7 with losses 8 for those frequencies not having desired characteristics.
• Fig. 2 The utilization of the arrangement of Fig. 2 can be extended so as to provide for wavelength division multiplexing capabilities on a waveguide structure. This is illustrated m Fig. 3 wherein initial light can be launched down a waveguide having a number of frequencies ⁇ l, ⁇ 2, ⁇ 3 coupled out of the waveguide by utilization of corresponding matched Bragg gratings 12, 13, 14 which operate so as to filter out the requisite frequencies.
• Fig. 4 illustrates a further arrangement whereby light coupled along waveguide 15 will be coupled to outputs 16, 17 by means of suitably matched Bragg grating 18 having desired periodic characteristics, matched to the desired frequencies for coupling.
• the surrounding waveguide refractive index regions eg. 19 can be tapered to provide for stronger coupling.
• the splitter arrangement of Fig. 4 has a Bragg grating coupled such that 50° of the light traverses along each of path 17, 18. This can be achieved for wavelengths twice the Bragg period. Of course, it is possible to ad ust the Bragg period to adjust the output angle and coupling efficiency.
• m Fig. 5 a Bragg grating 20 is provided for coupling around a bend for light travelling along the path 21, 22.
• a waveguide 110 m the form of a layer of photosensitive material has been deposited onto a substrate 112, eg. a silicon wafer having a native oxide layer for optical isolation of the waveguide material 110.
• a UV beam 116 from a UV source 114 is focussed (through optical elements 118) m the plane of the waveguide 110.
• the substrate 112 can be laterally moved as indicated by arrows 120 and 122 to effect writing of planes indicated by lines 124 of a first grating 126 of a grating structure 127, through UV-induced changes of the refractive index of the waveguide 110.
• a second grating 128 of the grating structure 127 is written by appropriate moving of the substrate 112.
• Light of a predetermined wavelength entering the waveguide 110 at predetermined angles of incidence on the gratings 126, 128 are confined to a path extending m the propagation direction 130 m the plane of the waveguide 110.
• the propagation characteristics of the waveguide 10 will therefore depend on the wavelength of a light signal 131 and an angle ⁇ under which it enters the waveguide 110.
• m the planar structure described above the grating confinement is limited to one- dimension m the plane of the waveguide 110.
• waveguides can be produced m a photosensitive waveguide material that are grating confined in two or three dimensions.
• holographic UV grating writing techniques using a phase mask 140 can be used to produce a waveguide 142 (propagation direction as indicated by arrow 141) within a block 144 of photosensitive waveguide material which is grating confined in two dimensions through gratings 146, 148 of a first grating structure 147 and gratings 150, 152 of a second grating structure 151 respectively.
• the one or more of the grating structures of a device could alternatively comprise a continuos grating whilst still effecting confinement of light of a predetermined wavelength entering at a predetermined angle of incidence on the grating structure.
• the resonator 250 shown in Figure 14 comprises two continuos grating structures 252, and 254 to effect channelling of light 256 of a predetermined wavelength entering the resonator 250 at a predetermined angle of incidence on the grating structures 252 and 254 around a ring path 258.
• Grating confinement can also be achieved in an optical fibre, e.g. using a cylindrical grating structure 320 around a guiding core 322 (propagation direction perpendicular to the drawing plane) of an optical fibre 324 as illustrated in Figure 12.
• the grating structure 320 effects confinement to a path extending in the propagation direction of light of a predetermined wavelength entering at a predetermined angle of incidence on the grating structure 320. It will be appreciated by a person skilled in the art that for a non-cylindrical grating structure confinement conditions can vary in different radial directions.
• grating confined waveguide propagation is the Bragg condition.
• This single equation contains within it the entire properties of grating confinement such as e.g. so- called photonic crystal fibres.
• Figure 8 shows the plot of resonant angle against grating period for the wavelength regime 1200-1600 nm for 1st, 2nd and 3rd order grating diffraction.
• variations in the resonant angle converge to within a few degrees, although the effect is largest for the 1st order.
• the physical interpretation is that for a large number of wavelengths the incident angle is approximately the same equating with similar diffraction properties. Therefore grating confinement will occur over a large bandwidth for a small input coupling angle at longer periods under identical launch conditions. Outside this regime radiation loss w ll occur. Other interesting properties are noted. There exist other regimes of incident angle at which total internal reflection can occur to enable propagation along the grating confined waveguide.
• K is the angle-dependent coupling coefficient for the grating
• L is the length of the grating
• ⁇ is the detuning of the wavevector, defined by
• a resonator 181 can be utilised for WDM (wavelength division multiplexing) filtering if the grating periods (which may be chirped) of gratings 182 and 184 of a first grating structure 183 and of gratings 186 and 188 of a second grating structure 187 are carefully selected such that a ring resonance is different for different wavelengths and therefore the outputs are spatially at different points.
• WDM wavelength division multiplexing
• a photonic crystal fibre 302 is located in line in a ring laser 304 (of any sort) to improve both linewidth, laser stability and mode selectivity (including transverse if multi-mode active fibre is used to increase power) . It is noted that a similar design can be applicable to linear lasers (of any sort) .
• a helical ring fibre laser 310 comprises an optical fibre 312 having a grating confined core structure 314 and spaced apart concave reflectors 315, 316 within the core structure 314.
• the helical ring fibre laser 310 can thus provide a circularly birefringent output (as indicated by arrow 311 ) .
• high power fibre lasers may be provided without using cladding pump configuration.
• single mode operation and good stability are possible, as well as large mode areas.
• the modes are grating diffraction dependent unlike conventional fibres which are aperture diffraction dependent.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Nanotechnology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Biophysics (AREA)
• Optical Integrated Circuits (AREA)
• Diffracting Gratings Or Hologram Optical Elements (AREA)
• Lasers (AREA)

Priority Applications (5)

Applications Claiming Priority (4)

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Cited By (6)

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Citations (7)

• 1999
  • 1999-11-12 EP EP99957723A patent/EP1129375A1/en not_active Withdrawn
  • 1999-11-12 JP JP2000582832A patent/JP2002530691A/ja not_active Withdrawn
  • 1999-11-12 CA CA002348995A patent/CA2348995A1/en not_active Abandoned
  • 1999-11-12 WO PCT/AU1999/001000 patent/WO2000029883A1/en active IP Right Grant
  • 1999-11-12 KR KR1020017006030A patent/KR20010089449A/ko not_active Application Discontinuation

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