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
  • G02B6/42—Coupling light guides with opto-electronic elements
  • G02B6/4201—Packages, e.g. shape, construction, internal or external details
  • G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
  • G02B6/422—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements
  • G02B6/4227—Active alignment methods, e.g. procedures and algorithms
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/0014—Monitoring arrangements not otherwise provided for
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S5/00—Semiconductor lasers
  • H01S5/02—Structural details or components not essential to laser action
  • H01S5/022—Mountings; Housings
  • H01S5/0225—Out-coupling of light

Definitions

• a waveguide is used to convey radiation that is outputted by a laser.
• the waveguide and the laser are usually included in different parts of a device.
• the waveguide must be aligned to the laser in order to properly convey the light outputted by the laser.
• the laser may be activated, may be induced to output radiation, and the radiation that passes through the waveguide may be measured - in order to determine the alignment.
• the activation of the laser during the alignment process may be costly and otherwise problematic - especially in devices that are manufactured in mass production.
• a method for aligning a laser unit to a waveguide unit may include (a) placing the laser unit in a tested position in which the laser unit faces the waveguide unit; (b) supplying light, via a coupler of the waveguide unit, to an alignment waveguide of the waveguide unit; (c) receiving light emitted from the alignment waveguide, wherein the light was emitted as result of the supplying of the light; (d) determining whether the light emitted from the alignment may include a spectral signature associated with an alignment unit of the laser unit; and (e) estimating whether the laser unit may be aligned to the waveguide unit based on the determining. [008] The supplying of the light and the receiving of the light while the laser unit may be deactivated, idle or otherwise non-active. The alignment is not based on a transmission of light by the laser.
• the method may include changing the tested position and jumping to supplying the light when determining that the laser unit may be misaligned to the waveguide unit.
• the method may include evaluating an amount of light that exited the coupled of the waveguide unit. Thus - if the supply is not sufficient due to misalignment between the source of light and the waveguide unit - the waveguide unit and/or the supplying element may be moved or otherwise be glued be better optically coupled to the alignment waveguide.
• the alignment unit may from a laser of the laser unit.
• the alignment unit may be the laser of the laser unit.
• the alignment waveguide may differ from a main waveguide that may be allocated for conveying radiation transmitted from a laser of the laser unit.
• the method may include attenuating light that passed through the alignment unit.
• the method may include attenuating light that passed through the alignment unit by an attenuating material that follows the alignment unit.
• the method may include attenuating light that passed through the alignment unit by a scattering element that follows the alignment unit.
• the method may include attenuating light that passed through the alignment unit by a termination of the alignment waveguide after the alignment unit.
• the alignment unit may be a first Bragg grating.
• the alignment unit may be a first Bragg grating and wherein the method may include attenuating light that passed through the first Bragg grating by a second Bragg grating.
• the method may include gluing the laser unit to a laser carrier following a completion of an alignment of the laser unit to the waveguide unit.
• a device may include a laser unit and a waveguide unit.
• the laser unit may include a laser and an alignment unit.
• the waveguide unit may include an alignment waveguide and a coupler.
• the coupler may be configured to receive light from a light source and to provide the light to the alignment waveguide.
• the alignment waveguide may be configured to direct the light towards the laser unit.
• the alignment unit When aligned to the waveguide unit the alignment unit may be configured to reflect light having a spectral signature of the alignment unit towards the alignment waveguide.
• the laser unit When misaligned to the waveguide unit the laser unit may be configured to reflect light without the spectral signature of the alignment unit towards the alignment waveguide.
• the alignment waveguide may be configured to direct the reflected light towards the coupler.
• the coupler may be configured to direct the reflected light towards a detector.
• the supplying of the light and the receiving of the light while the laser unit may be deactivated.
• the device may include changing the tested position and jumping to supplying the light when determining that the laser unit may be misaligned to the waveguide unit.
• the device may include evaluating an amount of light that exited the coupled of the waveguide unit.
• the alignment unit may differ from a laser of the laser unit.
• the alignment unit may be the laser of the laser unit.
• the alignment waveguide may differ from a main waveguide that may be allocated for conveying radiation transmitted from a laser of the laser unit.
• the device may include attenuating light that passed through the alignment unit.
• the device may include attenuating light that passed through the alignment unit by an attenuating material that follows the alignment unit.
• the device may include attenuating light that passed through the alignment unit by a scattering element that follows the alignment unit.
• the device may include attenuating light that passed through the alignment unit by a termination of the alignment waveguide after the alignment unit.
• the alignment unit may be a first Bragg grating.
• the alignment unit may be a first Bragg grating and wherein the method may include attenuating light that passed through the first Bragg grating by a second Bragg grating.
• the device may include gluing the laser unit to a laser carrier following a completion of an alignment of the laser unit to the waveguide unit.
• FIG. 1 is an example of testing equipment and of a device that includes a laser and one or more alignment units;
• FIG. 2 is an example of a device that includes a laser and one or more alignment units
• FIG. 3 is an example of a spectral response of an alignment unit and corresponding circuits
• FIG. 4 is an example laser unit that includes one or more alignment units
• FIG. 5 is an example laser unit that includes one or more alignment units
• FIGs. 6-9 are an examples a laser, a laser currier and a waveguide unit
• FIG. 10 is an example laser unit that includes one or more alignment units
• FIG. 11 is an example laser unit that includes one or more alignment units
• FIG. 12 is an example laser unit
• FIG. 13 is an example of a method.
• the device includes a first part that include the waveguide (waveguide unit) and a second part that includes the laser (laser unit).
• the first and second parts may be integrated circuits - such as waveguide integrated circuit (IC) and a laser IC (or or any type of IC).
• the laser IC has a first end that faces the waveguide IC and a second end that may include a mirror.
• the mirror may extend through the entire laser IC and reflects any light that reaches the mirror from the waveguide IC.
• the mirror may prevent to test the alignment of the laser without activating the laser - because the mirror reflects wide bandwidth which will include both the probe and the signal wavelength (substantially all the light it receives) and do not provide a reliable indication about the spatial relationship between the laser and the waveguide. Furthermore - on top of the mirror, the active layer has a very strong absorption, which also limits the alignment.
• the laser IC may be manufactured to include one or more alignment units (alignment units) that exhibit a frequency selective response - have a unique spectral signature (also referred to as signature) - once the waveguide is aligned to the one or more alignment units.
• alignment units alignment units
• signature unique spectral signature
• An alignment unit may be included in the laser - or may be be spaced apart from the laser- while maintaining a known spatial relationship with the laser.
• the known spatial relationship may be, for example, having the alignment unit located at a known displacement (over one or more axes) from the laser.
• the alignment process may proceed by introducing a relative movement between the laser IC and the waveguide IC to compensate for the known spatial relationship.
• the waveguide IC may include multiple waveguides - including an alignment waveguide that once aligned with the alignment unit - another waveguide of the waveguide IC - is aligned with the laser. The other waveguide will be used to cover light from the laser.
• the alignment unit may include a band pass filter, a Bragg grating, and the like - that may have a spectral response that appears once illuminated by a waveguide that is aligned to the alignment unit.
• the alignment unit may reflect towards the waveguide light of certain frequencies - while not reflecting other frequencies (to provide distinguishable spectral response). There other frequencies should not be returned (or at least should not be returned without being significantly attenuated) by the mirror towards the alignment unit and then to the waveguide.
• FIG. 1 is an example of testing equipment 11 and of a device 10 that includes a laser unit 30 and a waveguide unit 20.
• Light from a light source 12 propagates through a power splitter 16 and then exits a lightguide 18, impinges on a coupler 22 of the waveguide unit 20, enters an alignment waveguide 24 and propagates (via laser unit alignment waveguide 32) towards an alignment unit such as but not limited to a first Bragg grating 34.
• the laser may be passive (even not connected) and light reflected from the alignment unit 34 may be reflected towards the coupler 22 and may propagate through lightguide 18 towards coupler 22 and then to detector 14.
• Figure 1 also illustrate various parts of device 10 - an oxide layer (such as BE oxide layer) 21, BOX layer 23, silicon substrate 25, supporting legs 42.
• oxide layer such as BE oxide layer
• FIG. 2 is an example of a laser unit 30 and one or more alignment units 34 and 39.
• the laser unit 30 includes two laser unit alignment waveguides 32 and 37 that are positioned at both side of a main waveguide 25 (over which the transmissions from laser 32 propagate) and two alignment units 34 and 39 (one per each laser unit alignment waveguide).
• the laser unit alignment waveguides 32 and 37 are located at a known distance from the laser. There may be only one alignment unit, or more than two alignment units.
• the alignment waveguides 24 and 27 of the waveguide unit are aligned to the corresponding laser unit alignment waveguides 32 and 37 the light from the testing equipment will be reflected back to the testing equipment and will include the signature of one or more of the alignment units 34 and 39 respectively.
• the main waveguide 35 of the laser unit is aligned with the main waveguide 25 of the waveguide unit - and the waveguide unit is deemed to be aligned with the laser unit.
• the coupler may be a coupler MMI or any type of power monitor. It can also be a photo detector integrated in the waveguide unit for measuring the light from the lightguide that is fed to the alignment waveguide - and it is used for aligning the lightguide and the alignment waveguide.
• Either one of the alignment units may be illuminated during an alignment process - and the reflected light may exhibit the distinguishable spectral response - when aligned with the alignment waveguide.
• Figure 3 is an example of a spectral response 50 of an alignment unit and corresponding circuits.
• a signal which will be the pick reflected wavelength - obeying the Bragg condition, and a probe which will not be reflected by the grating.
• the ratio between the signal and the probe can provide an accurate information about the spatial position with respect to the alignment unit.
• This a response of a band pass filter Any other distinguishable spectral response may be provided.
• the ratio between the signal and probe could be an indication to the spatial position of the two units.
• Each auxiliary waveguide may include one or more Bragg gratings - for example two Bragg gratings. The first one reflects towards the waveguide IC some of the frequencies - while other frequencies propagate towards the second grating and are scattered by the second grating - in order to attenuate any frequency component of these other frequencies that propagates back to the waveguide IC.
• Laser includes a grating and light may penetrate and be selectively reflected.
• One more concept would be to use optical pumping of the laser. In this case we can illuminate the laser from top / bottom or along the optical axes with shorter wavelength which will cause optical pumping effect . This pumping will generate light at the unit laser wavelength which can be detected.
• the laser high absorption is for the unit wavelength of the laser.
• the alignment may involve using the laser as the alignment unit while using a different wavelength for which the QW will be relatively transparent. That wavelength could be reflected from a higher / lower order of the laser Brag grating, or a dedicated grating built into adjacent alignment structure / channel. This may allow to use lasers as an alignment unit without the regrowth process of a non attenuating layer. This may provide a significant cost reduction.
• Figure 4 is an example of a laser unit 30 that includes laser unit alignment waveguides 32 and 37, alignment unit such as first Bragg grating 34, laser unit main waveguide 35 and a second Bragg grating 35.
• alignment unit such as first Bragg grating 34
• laser unit main waveguide 35 and a second Bragg grating 35.
• the laser unit alignment waveguide 37 is shown without an alignment unit.
• the second Bragg Grating 34’ follows first Bragg grating 34.
• Light 61 reaches laser unit alignment waveguides 32 and impinges on first Bragg grating 34.
• the first Bragg grating 34 operates as a mirror which provide a reflected signal 62.
• the second Bragg grating 34’ scatters (64) or absorbs all (or a significant amount of) wavelengths 63 that were not reflected by the first Bragg grating, and prevent it from reaching the back wide band mirror 125.
• the existence of the second Bragg grating 34’ section could provide a better signal to noise ratio, but is not mandatory for the detection of the reflected signal.
• the second Bragg grating is an example of a scattering or absorbing or attenuating unit.
• the first Bragg grating may reflects specific wavelengths back into an alignment waveguide of the waveguide unit.
• the second Bragg grating may be use to scatter the other wavelengths toward the substrate of the laser IC (for example to locations outside the plane of figure 4 - this will improve the signal to noise ratio of the reflected light.
• Figure 4 is an example of a laser unit 30 that includes laser unit alignment waveguides 32 and 37, alignment unit such as first Bragg grating 34, laser unit main waveguide 35 and a second Bragg grating 35.
• alignment unit such as first Bragg grating 34
• laser unit main waveguide 35 and a second Bragg grating 35.
• the laser unit alignment waveguide 37 is shown without an alignment unit.
• Figure 5 is an example of a laser unit 30 that includes laser unit alignment waveguides 32 and 37, alignment unit such as first Bragg grating 34, laser unit main waveguide 35 and a second Bragg grating 35.
• alignment unit such as first Bragg grating 34
• laser unit main waveguide 35 and a second Bragg grating 35.
• the laser unit alignment waveguide 37 is shown without an alignment unit.
• the first laser unit alignment waveguides 32 is terminated and does not reach the end of the laser unit - thus at least a part of the radiation that passes the first Bragg grating 34 may be scattered or attenuated instead of returning towards the waveguide unit.
• Figures 6-9 illustrates an example of a laser 720 mounted on a laser carrier.
• the laser carrier includes:
• Supporting elements such as four vertical bars 714 that extend from the base and have upper ends that contact the laser and support the laser.
• the upper ends are positioned within a plane. Positioning the laser on the upper ends aligns the laser to the plane.
• the plane may be a horizontal plane or another plane.
• Elevated structure 711 that elevates above the base 710.
• a first part of the elevated structure has sidewalls that are confined within an imaginary region that corresponds to the base of the laser - so that once the laser is positioned on the upper ends, the sidewalls of the first part do not extend to the side of the laser.
• a insulator 713 positioned on the top of the elevated structure - of forming a part of the top of the elevated structure. The insulator isolates the conductive pad from the elevated structure and prevents cross talk (through adjacent insulating structures) between adjacent lasers.
• Conductive pad 712 that is positioned on top of the insulator.
• the conductive pad is electrically coupled to a terminal of the laser by an coupling material that is placed on at least a first part of the pad and a bottom of the laser.
• the coupling material may also glue the laser to the laser carrier. Because the conductive pad 712 is positioned on top of the elevated structure - excess coupling material does not aggregate and touches the sidewalls of the laser - and do not cause the laser to malfunction. The excess material may fall from the conductive pad / sidewalls of the elevated structure.
• Bond wire 722 that is electrically coupled to the second part of the conductive pad - for supplying signals to the laser via the conductive pad.
• Waveguides 716 - such as three waveguides - a middle waveguide through which the laser will output signals after being aligned, and two side optical waveguides that point to alignment units for aligning the laser.
• Mechanical bumps 717 that are slightly longer than waveguides 716- for contacting the laser and maintaining a micron scale distance between the laser and the waveguides 716.
• a glue with an appropriate optical refraction index may be placed between the laser and the waveguides 716.
• the conductive pad includes two rectangular regions that are connected to each other by a thinner line. Other shapes may be provided.
• Figure 10 is an example of a laser unit 30 that includes laser unit alignment waveguide 32”, laser unit main waveguide 35 and laser unit alignment waveguide 37”.
• Both laser unit waveguide units may return the radiation - even without substantially changing the spectrum of the radiation.
• the emitted light may be fully returned to the waveguide unit.
• This example illustrates a simple power signal looped back by any means in the laser photonics integrated circuit (PIC).
• a Bragg grating is followed by attenuating material 38 or any absorbing / scattering optical element such as bended / scattering waveguide.
• the elimination / scattering of the probe wavelength is a key element for high signal to probe extinction ratio.
• the attenuating material can be made of QW. Wavelength which will not be reflected from the Bragg grating, will be highly attenuated absorbed by the attenuating material.
• the attenuating material may include a combination of a material from column 3 of the periodic table and a material from column 5 of the periodic table.
• Figure 12 illustrates a laser unit in which the laser 32 and the main waveguide are provided and the laser, one illuminated, outputs (even when passive) a radiation of a certain spectral signature that differs from the light reflected from other parts of the laser unit.
• the main waveguide should be aligned to a corresponding main waveguide of the waveguide unit .
• Figure 13 illustrates method 900.
• Method 900 may be for aligning a laser unit to a waveguide unit, the method may include:
• step 920 If, for example, not finding the signature, then determining that alignment was not obtained. This may be followed by selecting a new tested position and then jumping to step 920.
• the supplying of the light and the receiving of the light while the laser unit may be deactivated, idle or otherwise non-active.
• the alignment is not based on a transmission of light by the laser.
• the method may include changing the tested position and jumping to supplying the light when determining that the laser unit may be misaligned to the waveguide unit.
• the method may include evaluating an amount of light that exited the coupled of the waveguide unit. Thus - if the supply is not sufficient due to misalignment between the source of light and the waveguide unit - the waveguide unit and/or the supplying element may be moved or otherwise be glued be better optically coupled to the alignment waveguide.
• the alignment unit may from a laser of the laser unit.
• the alignment unit may be the laser of the laser unit.
• the alignment waveguide may differ from a main waveguide that may be allocated for conveying radiation transmitted from a laser of the laser unit.
• the method may include attenuating light that passed through the alignment unit.
• the method may include attenuating light that passed through the alignment unit by an attenuating material that follows the alignment unit.
• the method may include attenuating light that passed through the alignment unit by a scattering element that follows the alignment unit.
• the method may include attenuating light that passed through the alignment unit by a termination of the alignment waveguide after the alignment unit.
• the alignment unit may be a first Bragg grating.
• the alignment unit may be a first Bragg grating and wherein the method may include attenuating light that passed through the first Bragg grating by a second Bragg grating.
• the method may include gluing the laser unit to a laser carrier following a completion of an alignment of the laser unit to the waveguide unit.
• any module or chip may include at least the components included in the figures and/or in the specification, only the components included in the figures and/or the specification.
• any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved.
• any two components herein combined to achieve a particular functionality may be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components.
• any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality.
• any reference signs placed between parentheses shall not be construed as limiting the claim.
• the word‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim.
• the terms“a” or“an,” as used herein, are defined as one or more than one.

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• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Optical Integrated Circuits (AREA)
• Optical Couplings Of Light Guides (AREA)

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• 2019
  • 2019-06-03 CN CN201980050043.1A patent/CN112912778B/zh active Active
  • 2019-06-03 WO PCT/IB2019/054584 patent/WO2019234589A2/en unknown
  • 2019-06-03 EP EP19815236.5A patent/EP3803483A4/en active Pending

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