WO2009097109A1 - Methods and systems for aligning optical packages - Google Patents
Methods and systems for aligning optical packages Download PDFInfo
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- WO2009097109A1 WO2009097109A1 PCT/US2009/000531 US2009000531W WO2009097109A1 WO 2009097109 A1 WO2009097109 A1 WO 2009097109A1 US 2009000531 W US2009000531 W US 2009000531W WO 2009097109 A1 WO2009097109 A1 WO 2009097109A1
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- conversion device
- wavelength conversion
- set point
- beam spot
- alignment set
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
- G01B11/27—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
- G01B11/272—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes using photoelectric detection means
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- 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
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
- G02B6/4214—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/37—Non-linear optics for second-harmonic generation
- G02F1/377—Non-linear optics for second-harmonic generation in an optical waveguide structure
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
- G02F1/3544—Particular phase matching techniques
- G02F1/3546—Active phase matching, e.g. by electro- or thermo-optic tuning
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- 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
- H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
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- 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
- H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
- H01S5/0071—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for beam steering, e.g. using a mirror outside the cavity to change the beam direction
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- 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
- H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
- H01S5/0092—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
Definitions
- the present invention generally relates to semiconductor lasers, laser controllers, optical packages, and other optical systems incorporating semiconductor lasers. More specifically, the present invention relates to methods and systems for aligning optical packages that include, inter alia, a semiconductor laser and a second harmonic generation (SHG) crystal or another type of wavelength conversion device.
- SHG second harmonic generation
- Short wavelength light sources can be formed by combining a single-wavelength semiconductor laser, such as an infrared or near-infrared distributed feedback (DFB) laser, distributed Bragg reflector (DBR) laser, or Fabry-Perot laser, with a light wavelength conversion device, such as a second harmonic generation (SHG) crystal.
- a single-wavelength semiconductor laser such as an infrared or near-infrared distributed feedback (DFB) laser, distributed Bragg reflector (DBR) laser, or Fabry-Perot laser
- DFB distributed feedback
- DBR distributed Bragg reflector
- Fabry-Perot laser Fabry-Perot laser
- the SHG crystal is used to generate higher harmonic waves of the fundamental laser signal.
- the lasing wavelength is preferably tuned to the spectral center of the wavelength converting SHG crystal and the output of the laser is preferably aligned with the waveguide portion at the input facet of the wavelength converting crystal.
- Waveguide optical mode field diameters of typical SHG crystals can be in the range of a few microns.
- PPLN periodically poled lithium niobate
- one object of the present invention is to provide methods and systems for aligning components in optical packages that utilize a laser diode in conjunction with an SHG crystal or other type of wavelength conversion device to generate shorter wavelength radiation (e.g., green laser light) from a longer wavelength source (e.g., a near-infrared laser diode).
- a method for aligning an optical package having a laser, a wavelength conversion device and at least one adjustable optical component includes using the adjustable optical component to direct a beam spot of the laser onto an input face of the wavelength conversion device.
- the adjustable optical component may comprise an adjustable micro-electro mechanical system (MEMS) mirror used in conjunction with a single lens to direct a beam spot of the laser onto an input face of the wavelength conversion device.
- MEMS micro-electro mechanical system
- a first scan of the beam spot across the input face of the wavelength conversion device on a fast scan line is then performed while measuring the output intensity of the wavelength conversion.
- the first scan is performed by oscillating the adjustable optical component about a first scanning axis at an approximate resonant frequency of the adjustable optical component.
- the first scan of the beam spot is then stepped along an orthogonal scan line to generate an output intensity for each of a plurality of fast scan lines.
- a first alignment set point along the orthogonal scan line is then determined based on the output intensities for each of the plurality of fast scan lines.
- a second scan of the beam spot is then performed over the fast scan line containing the first alignment set point while measuring the output intensity of the wavelength conversion device such that an output intensity for each point along the second scan.
- a second alignment set point is then determined based on the output intensities measured along the fast scan line containing the first alignment set point.
- the first alignment set point and the second alignment set point define a position where the beam spot is aligned with the waveguide portion of the wavelength conversion device.
- the beam spot is then positioned on the waveguide portion of the wavelength conversion device using the first alignment set point and the second alignment set point.
- a method for aligning a beam spot with a waveguide portion of a wavelength conversion device includes rapidly scanning a beam spot across the input face of the wavelength conversion device along a fast scan line by adjusting a position or state of an adjustable optical component while measuring the output intensity of the wavelength conversion device.
- the rapid scan of the beam spot is then stepped along an orthogonal scan line to generate a plurality of output intensities for each of a plurality of fast scan lines.
- a first alignment set point along the orthogonal scan line is then determined based on the average output intensity for each fast scan line.
- a slow scan of the beam spot is then performed over the fast scan line containing the first alignment set point while measuring the output intensity of the wavelength conversion device such that a plurality of output intensity for a plurality of points along the fast scan line containing the first alignment set point are generated.
- a second alignment set point is then determined based on the output intensities measured along the fast scan line containing the first alignment set point.
- the first alignment set point and the second alignment set point define a position where the beam spot is aligned with the waveguide portion of the wavelength conversion device.
- the beam spot is then positioned on the waveguide portion of the wavelength conversion device using the first alignment set point and the second alignment set point.
- an optical system in another embodiment, includes a laser, a wavelength conversion device, a lens assembly, one or more adjustable optical components, an optical detector, and a controller.
- the wavelength conversion device includes a wave guide portion and an input face.
- the optical detector is coupled to the controller and positioned to measure the output intensity of the wavelength conversion device.
- the lens assembly and the adjustable optical component are configured to direct a beam spot of the laser towards the input face of the wavelength conversion device.
- the controller is configured to control the position of the adjustable optical component about a first scanning axis and a second scanning axis such that the beam spot of the laser may be positioned on the input face of the waveguide conversion device.
- the controller may also be configured to: perform a first scan of the beam spot across the input face of the waveguide device along a fast scan line while stepping the first scan along an orthogonal scan line; determine a first alignment set point based on a plurality of output intensities for a plurality of fast scan lines; perform a second scan of the beam spot over the fast scan line containing the first alignment set point; and determine a second alignment set point based on the output intensities measured during the second scan.
- the controller may also be configured to position the adjustable optical component using the first and second alignment set points such that the beam spot is aligned with the waveguide portion of the wavelength conversion device.
- FIG. 1 is a schematic illustration of a MEMS mirror-enabled optical alignment package according to one embodiment of the present invention
- Fig. 2 is a schematic illustration of a beam spot on an input face of a wavelength conversion device.
- Fig. 3 is a schematic illustration of a rapid scan of the beam spot over an input face of the wavelength conversion.
- Fig. 4 is a schematic illustration of a slow scan of the beam spot over a fast scan line containing the first alignment set point on an input face of the wavelength conversion device.
- FIG. 1 Although the general structure of the various types of optical packages in which the concepts of particular embodiments of the present invention can be incorporated is taught in readily available technical literature relating to the design and fabrication of frequency or wavelength-converted semiconductor laser sources, the concepts of particular embodiments of the present invention may be conveniently illustrated with general reference to an optical package including, for example, a semiconductor laser 10 (labeled “ ⁇ ” in Fig. 1) and a wavelength conversion device 20 (labeled “2v” in Fig. 1). In the configuration depicted in Fig.
- the near infrared light emitted by the semiconductor laser 10 is coupled into a waveguide portion of the wavelength conversion device 20 by one or more adjustable optical components 30 and a suitable lens assembly 35, which lens assembly 35 may comprise one or more optical elements of unitary or multi-component configuration.
- the optical package illustrated in Fig. 1 is particularly useful in generating a variety of shorter wavelength laser beams from a variety of longer wavelength semiconductor lasers and can be used, for example, as a visible laser source in a laser projection system.
- the adjustable optical component 30 is particularly helpful because it is often difficult to focus the output beam emitted by the semiconductor laser 10 into the waveguide portion of the wavelength conversion device 20.
- waveguide optical mode field diameters of typical SHG crystals such as MgO-doped periodically poled lithium niobate (PPLN) crystals
- PPLN periodically poled lithium niobate
- the lens assembly 35 cooperates with the adjustable optical component 30 to generate a beam spot 15 of comparable size on the input face 22 of the wavelength conversion device 20.
- the adjustable optical component 30 is configured to introduce beam angular deviation by adjusting a drive mechanism of the adjustable optical component and, as such, can be used to actively align the beam spot 15 with the waveguide portion 24 of the wavelength conversion device 20 by altering the position of the beam spot 15 on the input face 22 of the wavelength conversion device 20 until it is aligned with the waveguide portion 24 of the wavelength conversion device 20.
- beam alignment may be monitored by providing, for example, a beam splitter 40 and an optical detector 50 in the optical path of the wavelength conversion device 20.
- the optical detector 50 may be operably connected to a microcontroller or controller 60 (labeled " ⁇ c" in Fig. 1) such that an output signal from the optical detector 50 is received by the controller 60.
- the controller 60 may be configured to control the position or state of the adjustable optical component 30 by adjusting a drive mechanism of the adjustable optical component and, as such, position the output beam of the semiconductor laser 10 on the input face 22 of the wavelength conversion device 20.
- the controller 60 may be used to control the position or state of the adjustable optical component 30 as a function of the output signal received from the optical detector 50.
- the controller 60 may be used to perform an alignment routine such that the beam spot 15 of the semiconductor laser 10 is aligned with the waveguide portion 24 of the wavelength conversion device 20.
- the adjustable optical component illustrated schematically in Fig. 1 can take a variety of conventional or yet to be developed forms.
- the drive mechanism of the adjustable optical component 30 may comprise one or more movable micro-opto-electromechamcal systems (MOEMS) or micro-electro-mechanical system (MEMS) operatively coupled to a mirror.
- MOEMS micro-opto-electromechamcal systems
- MEMS micro-electro-mechanical system
- the MEMS or MOEMS devices may be configured and arranged to vary the position of the beam spot 15 on the input face 22 of the wavelength conversion device 20. Since the mirror is located in the collimated or nearly- collimated beam space of the optical system, adjustment of the mirror angle will result in a change in the x/y position of the refocused beam spot at the input face of the wavelength conversion device.
- a MEMS mirror with a +/- 1 degree mechanical deflection when used in conjunction with a 3 mm focal length lens, may allow the beam spot to be angularly displaced +/- 100 ⁇ m on the input face of the wavelength conversion device.
- the adjustment of the beam spot may be done at frequencies on the order of 100 Hz to 10 kHz due to the fast response time of the MEMS or MOEMS device.
- the adjustable optical component 30 may comprise one or more liquid lens components configured for beam steering and/or beam focusing.
- the adjustable optical component 30 may comprise one or more mirrors and/or lenses mounted to micro-actuators.
- the adjustable optical component takes the form of a movable or adjustable lens in the lens assembly 35 and the otherwise adjustable optical component 30 takes the form of a fixed mirror.
- the adjustable optical component 30 is a micro-opto-electromechanical mirror incorporated in a relatively compact, folded-path optical system.
- the adjustable optical component 30 is configured to fold the optical path such that the optical path initially passes through the lens assembly 35 to reach the adjustable optical component 30 as a collimated or nearly collimated beam and subsequently returns through the same lens assembly 35 to be focused on the wavelength conversion device 20.
- This type of optical configuration is particularly applicable to wavelength converted laser sources where the cross-sectional size of the laser beam generated by the semiconductor laser is close to the size of the waveguide on the input face of the wavelength conversion device 20, in which case a magnification close to one would yield optimum coupling in focusing the beam spot on the input face of the wavelength conversion device 20.
- reference herein to a "collimated or nearly collimated" beam is intended to cover any beam configuration where the degree of beam divergence or convergence is reduced, directing the beam towards a more collimated state.
- the lens assembly 35 can be described as a dual function, collimating and focusing optical component because it serves to collimate the divergent light output of the laser and the refocus the laser light propagating along the optical path of the package into the waveguide portion of the wavelength conversion device.
- This dual function optical component is well suited for applications requiring magnification factors close to one because a single lens assembly 35 is used for both collimation and focusing. More specifically, as is illustrated in Fig. 1, laser light output from the semiconductor laser 10 is, in sequence, refracted at the first face 31 of the lens assembly 35, refracted at the second face 32 of the lens assembly 35, and reflected by the adjustable optical component 30 in the direction of the lens assembly 35.
- the laser light is reflected back in the direction of the lens assembly 35, it is first refracted at the second face 32 of the lens assembly 35 and subsequently refracted at the first face 31 of the lens assembly 35, for focusing on the input face of the wavelength conversion device 20.
- the adjustable optical component 30 is placed close enough to the image focal point of the lens assembly 35 to ensure that the principle ray incident on the input face 22 of the wavelength conversion device 20 is approximately parallel to the principle ray at the output of the optical package. It may also be shown that the configuration illustrated in Fig. 1 also presents some advantages in term of aberration. Indeed, when the output face of the semiconductor laser 10 and the input face of the wavelength conversion device 20 are positioned in approximate alignment with the object focal plane of the lens assembly 35 and the output waveguide of the semiconductor laser 10 and the input waveguide of the wavelength conversion device 20 are symmetric with respect to the optical axis of the lens assembly 35, it is contemplated that anti symmetric field aberrations, such as coma, can be automatically corrected.
- a method of aligning the beam spot 15 of the semiconductor laser 10 with the waveguide portion 24 of the wavelength conversion device 20 comprises traversing the beam spot 15 across the input face 22 of the wavelength conversion device 20 while monitoring the output of the wavelength conversion device 20 in order to determine a first alignment set point 16 and a second alignment set point 17 where the beam spot 15 is aligned with the waveguide portion 24 of the wavelength conversion device 20.
- the output intensity of the wavelength conversion device 20 may be monitored by positioning a beam splitter 40 and optical detector 50 proximate the output of the wavelength conversion device 20.
- the optical detector 50 may be a photodiode configured to measure the intensity of electro -magnetic radiation coupled through the wavelength conversion device 20.
- the electro-magnetic radiation may comprise infrared radiation, such as the infrared radiation emitted from the semiconductor laser 10, or visible light radiation, such as the green light emitted from the wavelength conversion device 20.
- the beam spot 15 of the semiconductor laser 10 is focused on the input face 22 of the wavelength conversion device 20. This may be accomplished by positioning the lens assembly 35 relative to the wavelength conversion device 20 and the semiconductor laser 10 such that the input face 22 of the wavelength conversion device 20 and the output face of the semiconductor laser 10 are substantially co-planar with the focal plane of the lens assembly 35.
- a relatively rapid scan of the beam spot 15 (as compared to a subsequent slow scan of the beam spot 15) is then performed over the input face 22 of the wavelength conversion device 20 along a fast scan line (Al), as shown in Fig. 3, while the output intensity (I) of the wavelength conversion device 20 is measured by the optical detector 50.
- the controller 60 rapidly adjusts the position or state of the adjustable optical component 30 about a first scanning axis which, in turn, causes the beam spot 15 incident on the input face 22 of the wavelength conversion device 20 to traverse the input face 22 of the wavelength conversion device 20 along a fast scan line.
- the adjustable optical component is oscillated about a first scanning axis by applying an oscillating signal, such as a sinusoidal signal, square wave signal, saw-tooth signal or the like, to a drive mechanism, such as a micro-actuator or MEMS device, to oscillate the adjustable optical component 30 about the first scanning axis.
- an oscillating signal such as a sinusoidal signal, square wave signal, saw-tooth signal or the like
- a drive mechanism such as a micro-actuator or MEMS device
- the drive mechanism of the adjustable optical component 30 is oscillated about the first scanning axis at a frequency significantly higher than the signal integration of the optical detector 50 positioned at the output of the wavelength conversion device 20 such that the measured output intensity (I) of the wavelength conversion device is representative of the average output intensity of the wavelength conversion device 20 over the fast scan line along which the beam spot 15 traverses.
- the signal integration of the optical detector 50 is sufficiently faster than the frequency at which the adjustable optical component is oscillated and, accordingly, the output intensity (I) of the wavelength conversion device is representative of the maximum output intensity over the fast scan line along which the beam spot 15 traverses.
- the drive mechanism of the adjustable optical component 30 may be oscillated at its approximate resonant frequency. This may be accomplished by oscillating the drive mechanism of the adjustable optical component with an oscillating signal having a frequency at or near the first eigen frequency of the drive mechanism of the adjustable optical component.
- the adjustable optical component is a MEMS mirror having a resonant frequency of about 500 Hz
- the MEMS mirror may be oscillated about the first scanning axis at about 500 Hz by applying a sinusoidal signal having a frequency of about 500 Hz to the corresponding axis of the MEMS mirror.
- the adjustable optical component comprises a MEMS mirror
- oscillating the MEMS mirror at an approximate resonant frequency provides a large amplitude displacement of the mirror about a scanning axis at high frequency (and a large displacement of the beam spot on the face of the wavelength conversion device) with minimum power consumption.
- the controller 60 steps the rapid scan of the beam spot 15 over the input face 22 of the wavelength conversion device 20 by rotating the adjustable optical component 30 about a second scanning axis perpendicular to the first scanning axis. This causes the rapid scan of the beam spot 15 to traverse across the input face 22 of the wavelength conversion device 20 along an orthogonal scan line (e.g., A2 in Figs.
- the second scanning axis of the adjustable optical component 30 corresponds to an axis parallel to the x-axis of the coordinate system shown in Figs. 1 and 3-4 while the orthogonal scan line along the input face 22 of the wavelength conversion device 20 corresponds to a line parallel to the y-axis of the coordinate system depicted in Figs. 1 and 3- 4.
- the average output intensity or maximum output intensity for each of the plurality of fast scan lines are then recorded by the controller 60 as a function of the orientation of the adjustable optical component 30 about the second scanning axis as shown in Fig. 3.
- first scanning axis of the adjustable optical component 30 will be generally perpendicular to the fast scan lines along the input face 22 and the second scanning axis of the adjustable optical component 30 will be generally perpendicular to the orthogonal scan line along the input face 22.
- the controller 60 determines a first alignment set point 16 based on the average output intensity of each of the plurality of fast scan lines. As shown in Fig. 3, the waveguide portion 24 of the wavelength conversion device 20 is positioned along the fast scan line having the greatest average output intensity.
- the first alignment set point 16 is determined to corresponds to a point along the orthogonal scan line through which the fast scan line containing the waveguide portion 24 of the wavelength conversion device 20 passes which, in turn, corresponds to a rotational orientation of the adjustable optical component 30 about the second scanning axis such that the beam spot 15 is positioned on the fast scan line containing the waveguide portion 24 of the wavelength conversion device 20.
- the measured output of the intensity is the maximum output intensity for each of the fast scan line
- the first alignment set point 16 is determined to correspond to a point along the orthogonal scan line through which the fast scan line having the greatest maximum output intensity of the plurality of fast scan lines passes.
- the beam spot 15 is then scanned across the input face 22 of the wavelength conversion device 20 along the fast scan line containing the first alignment set point.
- a relatively slow scan (as compared to the rapid scan) of the beam spot 15 along the fast scan line containing the first alignment set point 16 is performed.
- the controller 60 first orients the adjustable optical component 30 about the second scanning axis such that the beam spot 15 is located on the fast scan line containing the first alignment set point 16.
- the controller 60 then traverses the beam spot 15 over the fast scan line containing the first alignment set point 16 while measuring the output intensity (I) of the wavelength conversion device using the intensity sensor 50.
- the controller 60 traverses the beam spot 15 over the fast scan line by incrementally rotating the adjustable optical component 30 about the first scanning axis such that the beam spot 15 is positioned at discrete points along the fast scan line containing the first alignment set point 16. Accordingly, the output of the optical detector 50 during the slow scan is representative of the output of the wavelength conversion device 20 for each discrete position of the beam spot 15 along the fast scan line.
- the slow scan of the beam spot 15 along the fast scan line may be facilitated by applying a signal to a micro-actuator or MEMS device to rotate the adjustable optical component 30 about the first scanning axis and thereby slowly scan the beam spot 15 over the fast scan line.
- the signal used in the slow scan may be such that, if the beam spot 15 has a width Wl in the direction of the fast scan line and the waveguide portion 24 has a width W2 along the fast scan line, then the scanning period T (e.g., the time it takes for the beam spot to traverse along the scan line) multiplied by the scan speed V (e.g., speed at which the beam spot traverses the fast scan line) is less than the sum W1+W2 (e.g., V*T ⁇ (W1+W2)).
- the output intensity (I) corresponding to each discrete position of the beam spot 15 is recorded by the controller 60 during the slow scan as a function of the orientation of the adjustable optical component 30 about the first scanning axis as shown in Fig. 4.
- a rapid scan of the beam spot 15 is then performed across the input face 22 of the wavelength conversion device 20 along the fast scan line containing the first alignment set point to determine a second alignment set point.
- the controller first orients the adjustable optical component 30 about the second scanning axis such that the beam spot 15 is located on the fast scan line containing the first alignment set point 16.
- the controller 60 then rapidly traverses the beam spot 15 over the fast scan line containing the first alignment set point 16 by oscillating the adjustable optical component about the first scanning axis while measuring the output intensity (I) of the wavelength conversion device using the optical detector 50, in a similar manner as described hereinabove.
- the signal integration of the optical detector 50 may be sufficiently faster than the frequency at which the adjustable optical component is oscillated such that the output of the optical detector corresponds to the output intensity (I) for each discrete point along the fast scan line.
- the output intensity corresponding to each discrete position of the beam spot 15 along the fast scan line is recorded by the controller 60 during the rapid scan as a function of the orientation of the adjustable optical component 30 about the first scanning axis as shown in Fig. 4.
- the controller 60 determines a second alignment set point 17 based on the output intensities received from the optical detector 50 during the scan. As shown in Fig. 4, the waveguide portion 24 of the wavelength conversion device 20 is positioned at a point on the fast scan line corresponding to the beam spot position having the greatest output intensity.
- the second alignment set point 17 is determined to be the position of the beam spot 15 along the fast scan line corresponding to the greatest output intensity of the wavelength conversion device 20 which, in turn, corresponds to a rotational orientation of the adjustable optical component 30 about the first scanning axis such that the beam spot 15 is positioned on the waveguide portion 24 of the wavelength conversion device 20.
- the second alignment set point 17 may be adjusted or tuned by measuring the output intensity of the wavelength conversion device 20 with the beam spot 15 positioned on points adjacent to the point on the fast scan line corresponding to the greatest output intensity and/or with the beam spot 15 positioned between the point having the greatest output intensity adjacent points.
- the second alignment set point 17 may then be interpolated along the fast scan line based on the measured output intensities of the adjacent points. In this manner the second alignment set point may be adjusted and tuned such that the output intensity of the wavelength conversion device is maximized.
- the second alignment set point 17 may be adjusted or tuned by performing another scan of the beam spot 15 over the fast scan line containing both the first and second alignment set points while measuring the output intensity of the wavelength conversion device 20.
- the output intensity of the wavelength conversion device 20 may be recorded by the controller as a function of the orientation of the adjustable optical component about the first scanning axis. For this scan, the range of the scan along the fast scan line containing the first alignment set point 16 may be limited to that portion of the fast scan line containing the second alignment set point 17.
- the signal applied to the adjustable optical component may be such that the scanning period T multiplied by the speed V at which the beam spot traverses the fast scan line is less than the mode diameter D of the waveguide portion 24 of the wavelength conversion device (e.g., V*T ⁇ D).
- the product V*T may be less than a predetermined percentage of the mode diameter.
- the product V*T may be less than 10% of the mode diameter (e.g., V*T ⁇ .10*D).
- the second alignment set point 17 may then be adjusted or tuned based on the output intensities and orientations recorded during the scan such that the output intensity of the wavelength conversion device is maximized.
- the controller 60 may then utilize the first alignment set point 16 and the second alignment set point 17 to orient the adjustable optical component 30 about each of the first scanning axis and the second scanning axis such that the beam spot 15 is incident on the waveguide portion 24 of the wavelength conversion device 20.
- the method described herein provides for the fast and efficient alignment of the beam spot 15 of the semiconductor laser 10 with the waveguide portion 24 of the wavelength conversion device 20. Referring to Fig.
- the waveguide portion 24 may be positioned on the input face 22 at one of up to N 2 discrete spatial locations.
- the present inventors have discovered that, using the rapid scan/slow scan alignment methodology described herein, only 2N discrete spatial measurements need to be made in order to locate the waveguide portion 24 and thereby align the beam spot 15 with the waveguide portion 24 of the wavelength conversion device 20.
- the alignment method of the present invention may be employed during the manufacture of the optical package.
- the wavelength conversion device 20 is assembled atop the semiconductor laser 10 such that the output face of the semiconductor laser 10 and the input face of the wavelength conversion device 20 are substantially co-planar.
- the adjustable optical component 30 and the lens assembly 35 are then positioned in the x/y plane and z direction with respect to the wavelength conversion device 20 and semiconductor laser 10.
- Each of the adjustable optical component 30 and lens assembly 35 are positioned in the x/y plane such that the centerline of each component is within a few hundred microns of the centerline between the semiconductor laser 10 and the wavelength conversion device 20.
- the lens assembly 35 and adjustable optical component 30 may be positioned in the optical package along the z- direction such that the input face 22 of the wavelength conversion device 20 and the output face of the semiconductor laser 10 are substantially in or coplanar with the object focal plane of the lens assembly 35.
- the focal length of the lens assembly 35 is about 3 mm. Therefore, the components of the optical package are positioned such that the distance between the lens assembly 35 and the input face 22 of the wavelength conversion device 20 and the output face of the semiconductor laser 10 may be about 3 mm.
- the adjustable optical component 30 is similarly positioned relative to the lens assembly 35.
- each of the lens assembly 35, the wavelength conversion device 20/semiconductor laser 10 combination and adjustable optical component 30 are then permanently fixed into place in the optical package using epoxy, laser welding, or other attachment techniques as may be presently known or subsequently developed.
- the optical package may be energized and the alignment method described herein may be performed by the controller 60 such that the beam spot 15 of the semiconductor laser 10 is aligned with the waveguide portion 24 of the wavelength conversion device 20. It should be understood that the alignment method described herein may be used to align the optical package during assembly of the optical package or after the entire optical package has been assembled and the optical package is powered on for the first time.
- the method of the present invention may be used in conjunction with feedback loop alignment techniques to fine tune the alignment of the beam spot 15 with the wavelength conversion device 20 as each component of the optical package is brought into alignment.
- the lens assembly 35 and adjustable optical component 30 may be inserted into the optical package and positioned in rough alignment with the wavelength conversion device 20 and semiconductor laser 10.
- the alignment of the components in the x/y plane need only be within a few hundred microns while the alignment of the lens assembly 35 with the input face 22 of the wavelength conversion device 20 should be close to one focal length of the lens assembly 35.
- the optical package is powered on and the alignment method describe herein is performed by the controller to align the beam spot 15 with the waveguide portion 24 of the wavelength conversion device 20.
- the lens assembly 35 and the adjustable optical component 30 may then be adjusted in the x/y plane and z direction to optimize the properties of the optical package while the controller 60 utilizes a separate feedback control loop alignment techniques to dynamically maintain the alignment of the beam spot 15 with the wavelength conversion device 20 as the position of each of the lens assembly 35 and the adjustable optical component 30 are adjusted.
- the method of the present invention may be utilized to align or realign the beam spot with the adjustable optical component after the optical package has been assembled and throughout the life of the optical package.
- realignment of the beam spot with the waveguide may be necessary if the assembled optical package is exposed to thermal or environmental conditions, mechanical shock or other conditions which may adversely impact beam-waveguide alignment.
- the alignment methods described herein may be performed under control of the controller operatively connected to the optical package.
- use of the alignment method described herein to realign the optical package may be performed automatically, such as when the controller detects a reduction in the output intensity of the optical package.
- the alignment method may be periodically performed throughout the life of the optical package.
- use of the alignment method described herein to realign the optical package may be initiated by a user.
- the actuator used to adjust the position of the adjustable optical component may be external to the optical package and operatively attached to the adjustable optical component for purposes of alignment only.
- the adjustable optical component may be adjusted by an internal actuator, integral with the optical package, such as when the adjustable optical component is a MEMS or MOEMS actuated mirror.
- the method described herein is suitable for aligning a beam spot of a semiconductor laser with a waveguide portion of a wavelength conversion device.
- the alignment method is particularly suited for performing the initial alignment of the beam spot with the wavelength conversion device during assembly of the optical package.
- the alignment method may also be used to maintain alignment or perform realignment of the beam spot with the wavelength conversion device during operation of the optical package or at any time during the life-cycle of the package.
- the methods of the present invention may be applicable to color image-forming laser projection systems, laser-based displays such as heads-up displays in automobiles, or any laser application where optical alignment and/or wavelength tuning are issues.
- references herein to a lens assembly and an adjustable optical component being "configured" to direct a laser beam in a particular manner denotes an existing physical condition of the lens assembly and the adjustable optical component and, as such, is to be taken as a definite recitation of the structural characteristics of the lens assembly and the adjustable optical component.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Optics & Photonics (AREA)
- Optical Couplings Of Light Guides (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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EP09705393A EP2238490A4 (en) | 2008-01-30 | 2009-01-27 | Methods and systems for aligning optical packages |
CN200980107457XA CN101960347A (en) | 2008-01-30 | 2009-01-27 | The method and system of optical package is used to align |
JP2010545008A JP2011511318A (en) | 2008-01-30 | 2009-01-27 | Method and system for aligning optical packages |
Applications Claiming Priority (2)
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US6297308P | 2008-01-30 | 2008-01-30 | |
US61/062,973 | 2008-01-30 |
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WO2009097109A1 true WO2009097109A1 (en) | 2009-08-06 |
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PCT/US2009/000531 WO2009097109A1 (en) | 2008-01-30 | 2009-01-27 | Methods and systems for aligning optical packages |
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US (1) | US7751045B2 (en) |
EP (1) | EP2238490A4 (en) |
JP (1) | JP2011511318A (en) |
KR (1) | KR20100106604A (en) |
CN (1) | CN101960347A (en) |
TW (1) | TW200945711A (en) |
WO (1) | WO2009097109A1 (en) |
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WO2009151559A1 (en) * | 2008-06-10 | 2009-12-17 | Corning Incorporated | Folded adjustable optical path in a frequency doubled semiconductor laser |
WO2010099252A3 (en) * | 2009-02-26 | 2010-12-02 | Corning Incorporated | Folded optical system with a lens having axial astigmatism |
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US20100272134A1 (en) * | 2009-04-22 | 2010-10-28 | Blanding Douglass L | Rapid Alignment Methods For Optical Packages |
US8139216B2 (en) * | 2009-11-20 | 2012-03-20 | Corning Incorporated | Optical package alignment systems and protocols |
US20110255089A1 (en) * | 2010-04-14 | 2011-10-20 | Vikram Bhatia | Methods for Aligning Wavelength Converted Light Sources |
US8294130B2 (en) * | 2010-06-11 | 2012-10-23 | Corning Incorporated | Methods and systems for optimizing the alignment of optical packages |
WO2012015596A1 (en) * | 2010-07-30 | 2012-02-02 | Corning Incorporated | Optical package and method for aligning optical packages |
US8325332B2 (en) * | 2010-07-30 | 2012-12-04 | Corning Incorporated | Start-up methods for frequency converted light sources |
WO2012018577A1 (en) * | 2010-08-06 | 2012-02-09 | Corning Incorporated | Frequency doubled laser with folded optical path |
JP6320737B2 (en) * | 2013-12-06 | 2018-05-09 | 株式会社日立情報通信エンジニアリング | High-precision alignment method and high-precision alignment apparatus for optical components |
US10705341B1 (en) * | 2017-07-07 | 2020-07-07 | Facebook Technologies, Llc | Temporally incoherent and spatially coherent source for waveguide displays |
US11402080B2 (en) * | 2019-05-23 | 2022-08-02 | Korrus, Inc. | Dynamic illumination using a coherent light source |
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2009
- 2009-01-23 TW TW098103139A patent/TW200945711A/en unknown
- 2009-01-27 KR KR1020107019079A patent/KR20100106604A/en not_active Application Discontinuation
- 2009-01-27 WO PCT/US2009/000531 patent/WO2009097109A1/en active Application Filing
- 2009-01-27 EP EP09705393A patent/EP2238490A4/en not_active Withdrawn
- 2009-01-27 CN CN200980107457XA patent/CN101960347A/en active Pending
- 2009-01-27 JP JP2010545008A patent/JP2011511318A/en active Pending
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Also Published As
Publication number | Publication date |
---|---|
KR20100106604A (en) | 2010-10-01 |
US7751045B2 (en) | 2010-07-06 |
JP2011511318A (en) | 2011-04-07 |
EP2238490A4 (en) | 2013-01-09 |
US20090190131A1 (en) | 2009-07-30 |
TW200945711A (en) | 2009-11-01 |
CN101960347A (en) | 2011-01-26 |
EP2238490A1 (en) | 2010-10-13 |
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