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
  • G02B6/24—Coupling light guides
  • G02B6/25—Preparing the ends of light guides for coupling, e.g. cutting
• • 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
  • G02B6/105—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type having optical polarisation effects
• • 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
  • G02B6/126—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 using polarisation effects
• • 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
  • G02B6/13—Integrated optical circuits characterised by the manufacturing method
• • 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
  • G02B2006/12166—Manufacturing methods
  • G02B2006/12176—Etching

Definitions

• the present invention relates broadly to laser ablation (or alternatively sometimes referred to as laser etching, hereinafter referred to as ablation) processing of waveguide structures .
• optical waveguide devices During the construction of optical waveguide devices, it is common that changes associated with a particular construction step occur which may affect the operational characteristics of the devices.
• optical devices are often constructed utilizing an adaptation of semiconductor fabrication techniques and can commonly include a number of layers constructed on a silicon substrate.
• various compressive stresses are induced during normal operating conditions. These stresses can have the effect of changing the operational characteristics of any device formed on the substrate.
• the compressive stresses can often give rise to anisotropic birefringent properties in optical waveguides which can substantially effect their operation.
• the present invention provides a method of processing an optical device incorporating a waveguide, the method comprising the step of utilizing a laser to heat a surface of the device, to alter an optical characteristic of the waveguide, and wherein the power density of the laser is selected to effect surface ablation.
• the laser may comprise a carbon dioxide laser source .
• the method may be utilized to alter the birefringent properties of the waveguide, e.g. the TM and TE birefringent modes may be substantially aligned.
• the step method may further comprise the step of may further comprise masking the surface with a thermally conductive material having an aperture defined therein to limit exposure of the device to the laser.
• the device may comprise a sensor.
• the method may further comprise the step of depositing a material layer on the surface. Accordingly, the method itself may be utilised to form the device.
• the device may eg. comprise a semiconductor device or a Si0 2 /Si planar waveguide device .
• Step of depositing the material layer may comprise depositing the material layer on portions of the surface affected by the ablation.
• the material layer may be provided as an electrode for electrically contacting the device.
• the method may further comprise the step of mounting a further component in a groove formed in the surface as a result of the ablation.
• the further component may comprise a modulator for modulating a characteristic of the device.
• the method may be conducted at different locations of the device so as to form an optical structure.
• the optical structure may comprise a grating structure.
• the optical structure may comprise a polarisation filter.
• the method may be used to diminish UV induced changes present in the waveguide.
• the device may comprise an optical fibre.
• the method may be utilised to mark the device by way of the ablation.
• the laser may comprise a semiconductor laser operating at a wavelength of more than about 1.8 micro metre. This wavelength range may be preferable where the surface of the device comprises Si0 2 .
• the method may further comprise the step of providing an absorber material to facilitate the heating of the surface of the device.
• the invention may alternatively be defined as providing an device incorporating a waveguide, wherein the device has been processed utilising a laser to heat a surface of the device, to alter an optical characteristic of the waveguide, and wherein the power density of the laser is selected to effect surface ablation.
• Fig. 1 illustrates schematically the operation of the method of the preferred embodiment
• Fig. 2 illustrates the ablation of a wafer surface
• Fig. 3 illustrates the change and effective index in an experiment utilizing the preferred embodiment
• Fig. 4 illustrates a further change in the effective index of an experiment utilizing the preferred embodiment
• Fig. 5 illustrates the initial profile of a Mach-
• Fig. 6 illustrates the spectral response for TE and TM modes of a MZ interferometer after application of the preferred embodiment for the device of Fig. 6;
• Fig. 7 illustrates an alternative form of processing a wafer;
• Fig. 8 illustrates the process of ablation around a core of a waveguide;
• Fig. 9 illustrates the utilization of ablation in changing the device characteristics of a waveguide
• Fig. 10 illustrates the utilization of ablation in conjunction with deposition of further layers on a wafer
• Fig. 11 illustrates the construction of a long period lossy grating. Description of Preferred and Other Embodiments
• an inexpensive and relatively compact C0 2 laser device is utilized to provide mid infrared laser processing of a waveguide structure so as to obtain both birefringence compensation and tuning of optical components.
• the processing set up is illustrated schematically in Fig. 1 wherein a waveguide 3 is subjected to ablation utilizing a C0 2 laser 5.
• An example of the ablation processing is illustrated in Fig. 2 wherein a waveguide 6 having a internal core 7 is processed so as to include ablation channels 8, 9.
• the processing set up is illustrated schematically in Fig. 1 wherein a waveguide 3 is subjected to ablation utilizing a C0 2 laser 5.
• An example of the ablation processing is illustrated in Fig. 2 wherein a waveguide 6 having a internal core 7 is processed so as to include ablation channels 8, 9.
• the first example the
• C0 2 laser was used to enhance the device characteristics of an asymmetric Mach-Zehnder (MZ) interferometer fabricated utilizing hollow-cathode PECVD techniques .
• MZ Mach-Zehnder
• the mid-IR radiation was used to thermally relax stresses at the core and substrate as well as affect a change in the refractive index.
• the core and cladding waveguide glasses can be softened, melted and vaporised.
• These ablation processes themselves can be used to generate faster relaxation than would otherwise be possible as well as provide a source of polarisation dependent loss for energy stripping within waveguides for functions such as optical attenuators, and for other more classical applications, including the laser ablation of stress-relieving grooves.
• Most heating was found to occur through non-radiative transfer of absorbed light into vibrational modes of the silica molecule.
• the substrate temperature was thought to be approximately the same as that induced at the surface.
• the laser was operated initially with unfocussed 10W of C power ( - 140W/cm 2 ) . When the laser was later focused, temperatures readily exceeding the melting point of silica were achieved resulting in laser vaporisation and ablation.
• birefringence compensation as measured by matched TE and TM spectra (the TM identified to have a higher effective index by writing a weak Bragg grating in a straight waveguide manufactured on the same wafer), can be achieved between the two couplers. From an experimental point of view, if true birefringence reduction in this region is demonstrated, the change in TE and TM notch wavelength due to an increase in effective index must be such that they converge when processing the longer arm, and diverge when processing the shorter arm. The reverse is the case for a decrease in refractive index.
• optical spectra were taken, of the MZ device using a broadband erbium-doped fibre amplifier (EDFA) and a spectrum analyser with a resolution of 0.05nm, limiting the birefringence splitting which can be measured to -lxlO "5 .
• EDFA erbium-doped fibre amplifier
• the longer arm of a MZ device (12um Si0 2 cladding and buffer layers, 4x5 ⁇ m Ge0 2 - doped core, . ⁇ n - 0.01) was processed for testing and confirmation of the concept. Measurements were taken at intervals after briefly halting the exposure at fixed times since the fibre coupling was increasingly affected by longer exposures.
• the power density of the C0 2 laser was then increased to -1.3kW/cm 2 by focussing to a lOO ⁇ m spot size such that we exceed the threshold necessary for vaporisation for an exposure of less then 0.2s. Ablation was confirmed under an optical microscope after gently cleaving through one damage region of the surface. By controlling the duration of the exposure it was possible to control the depth to which material is removed. The spectral responses when exposing the longer arm were found to shift to shorter wavelengths indicating a decrease in refractive index. However, the TM state was found to decrease more rapidly resulting in a large drop in the birefringence splitting.
• Fig. 4 shows the change in effective index as a function of shots fired in the same region and shows the convergence of birefringence when exposing the longer arm. It was noted that subsequent successive shots on the same region did not contribute any further. Indeed a small reversal was observed. Exposing the shorter arm showed spectral divergence, as expected if polarisation compensation has been achieved.
• Fig. 5 The spectral response for a second device utilized in experiments (essentially a polarisation splitter) prior to irradiation is shown in Fig. 5.
• the poor fringe contrast and the difference between TE and TM responses indicates that the input coupler is polarisation sensitive and that different amounts of light are split for each eigenstate.
• the intensity of light in each arm is not equal leading to poor fringe contrast upon recombination at the output coupler, particularly in this case of the TE state.
• the polarisation sensitivity between couplers is very difficult to eliminate completely in silica-on-silicon systems where strain is not readily removed.
• Fig. 6 illustrates the end results on the device once the process of irradiation ablation was optimised.
• the ablation of the waveguide can also be extended, as shown in Fig. 8, to the area surrounding the core 25. This can be utilized to effect the operation of the core and the overall device.
• Fig. 9 there is illustrated the utilization of ablation to form a refined surface 30 which can be utilized to provide for more accurate sensing by the core 31.
• the ablation of the surface can be utilized in the construction of complex semi-conductor devices having predetermined operational characteristics.
• Fig. 10 there is illustrated the example of deposition of a subsequent layer 33 which can comprise zinc oxide, BiT0 3 or the like so as to provide for a functional semiconductor device .
• a further example refinement is illustrated in
• Fig. 11 where a series of ablations 40-42 are written at regular intervals along a core 43 so as to provide for a long period "loss" grating structure.
• the aforementioned laser process has a number of other uses.
• it can be used to provide for accelerated aging of components by means of C0 2 thermal heating of optical devices such as UV processed gratings formed on a planar waveguide.
• the accelerated aging can provide for improved operational characteristics and can include precise localised aging of components.
• the thermal annealing can be utilized to anneal out the UV processing of portions of a previously processed waveguide. This can be taken to the extent of almost totally annealing out the UV processing effect.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Optical Integrated Circuits (AREA)

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• 1999
  • 1999-02-12 AU AUPP8655A patent/AUPP865599A0/en not_active Abandoned
• 2000
  • 2000-02-14 JP JP2000598880A patent/JP2002536698A/ja not_active Withdrawn
  • 2000-02-14 KR KR1020017010257A patent/KR20020003193A/ko not_active Application Discontinuation
  • 2000-02-14 WO PCT/AU2000/000099 patent/WO2000048024A1/en not_active Application Discontinuation
  • 2000-02-14 EP EP00904724A patent/EP1181588A4/de not_active Withdrawn
  • 2000-02-14 CA CA002361952A patent/CA2361952A1/en not_active Abandoned

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