`
`(19} World Intellectual Property
`Organization
`International Bureau
`
`(43} International Publication Date
`21 Aprii 2005 (21.04.2005)
`
`
`
`PCT
`
`lIlllllllllll|||||||||||||||||||||||||||||lllllllllllllllllllllll||||||||l|||||||||||||||ll||
`
`(10) International Publication Number
`W0 2005/036212 A2
`
`(51) International Patent Classification":
`
`C023
`
`(21’ Immafi‘ma' Applicatic’" “mm:
`PCT’U53003’038‘63
`
`[22) International Filing Date:
`9 Seplember 2003 (091092003)
`
`95’ F115“ Luguafl“:
`(26) Publication Language:
`
`English
`[English
`
`(71) Applicant [for at! designated States except US): EM-
`CORE CORPORATION [USJ'US];
`[45 Belmont Drive.
`Somerset. NJ 08873 (US).
`
`(81) Designated Slates (national): AE. AG. AL. AM. AT. AU.
`AZ, BA. BB. BG. BR. BY, BZ, CA. CH. CN. (KLCR. (Ill.
`(17,. D15, DK. DM. oz, 15C. 1515. as, it, GB. GD. (as. Gil.
`GM, HR. IIU. It). 1L, IN. ts, JP. KE. KG, KP. KR.
`LC.
`LK. LR. LS. LT. LU. LV. MA, MD. MG. MK, MN. MW.
`MX. MZ. N1. N0. NZ. OM. PG. PH. PL. in: no. RU. SC.
`SD. SE, SG. SK. 3]., SY, TI. TM. TN. TR. 'l‘l‘. T74, UA,
`no, as. uz, vc. VN. YU, 71A. 7M, 21w.
`
`{84) Designated States (regional): ARII’O patent (Gil. GM.
`KE, LS. MW, MZ, SD, SL. SZ, TZ. UG. ZM. ZW).
`[Eurasian patent (AM. AZ. BY. KG. KZ. MD. RU. TJ. 'l‘M J.
`European patent [A'I] BE. BG. CH, CY. (37.. DIS. DK. lili.
`IE5.
`]'-'l. FR. (ill. GR. HU. ill. IT. LU. MC. NL. PT. Rt).
`SE. SI. SK. TR), OAPl palcnl (BF. BJ. CF. CG, CI, CM.
`GA, GN, GQ. GW, ML. MR. NE, SN, TD. TG).
`
`(72) Inventors; and
`[75)
`lnventorampplteants (for US only): MIAO. Rongsheng
`[CNIUS]: 9925 Iowa Azusa Road. Temple City, CA 91780
`{US}. LOU, Xin, Simon [USJ'US]; 686 Bataan Place. Mon-
`published:
`lcrcy Park. CA 91755 (US). KHA. Leo IUSt'USI: 21490
`Cold Spring Lane. Diamond Bar. CA 9|?b5 (US). LOU, _
`without international Jean-h report and to be repubt't't‘hed
`Xiaoming [CNI'US]; 412 S. 3rd Avenue. #li Arcadia. CA
`upon receipt of that report
`91006 (US).
`
`[74) Agent: MARCELLI, Mark. 1.; Christie. Parker (it Hale.
`l.[.l’. 350 West Colorado Boulevard. Pasadena, CA 9| lOS
`{US}.
`
`.f'br m'a-tetter (odes and other abbreviations. refer to the "Guid-
`am)? Nora on Codes andrlbbmrian‘nm“ appearing at the begin-
`thing ofemfi reguiiar issue ofthe PCT Gazette.
`
`(54) Title: PIIOFODETECFURIOVFICAL FIBER APPARATUS WITH ENHANCED OPTICAL COUPLING EFFICIENCY
`AND Mirt'itoo FOR FORMING THIS SAME
`
`13
`1.?
`
`h/E, ti
`OB
`
`e7
`
`? _'_""‘-
`
`13
`s
`
`7%
`
`
`
`005/036212A2|||||||||||||||||||||||||||||||||ll||||||||||||||||||||||||||||||||||||l|||||||||||||||||||||||
`
`N (57) Abstract: An optical thick film formed on a photodctcctor improves the optical coupling efficiency between the optical fiber
`and photudctcctor which an: optically coupled. The optical thick film has a refractive index that is between the refractive index of
`air and the refractive index of photodctcctor upon which the optical matching coating is disposed. Silicone may advantageously he
`former] as the optical thick film coating on the photodeteclor
`
`W0
`
`001
`
`Apple Inc.
`APL 10 15
`
`US. Patent No. 8,929,965
`FITBIT, Ex. 1015
`
`Apple Inc.
`APL1015
`U.S. Patent No. 8,929,965
`
`001
`
`FITBIT, Ex. 1015
`
`
`
`W0 20%!036212
`
`PCTIUSZOGSIUZBIGZ
`
`PHOTODETECTOR/OPTICAL FIBER APPARATUS WITH ENHANCED OPTICAL
`
`COUPLING EFFICIENCY AND METHOD FOR FORMING THE SAME
`
`FIELD OF THE INVENTION
`
`The
`
`present
`
`invention
`
`relates, most
`
`generally,
`
`to
`
`optoelectronic
`
`telecommunications systems. More particularly, the present invention relates to an
`
`assembly including an optical
`photodetector.
`
`transmission medium optically coupled to a
`
`airlphotodetector interface.
`
`is coupled into the active area of a photodetector either by a lens or by direct
`fiber,
`fiber coupling, depending on application. The optical coupling region typically
`includes an air gap between the optical fiber and photodetector and, when a lens is
`
`BACKGROUND OF THE INVENTION
`
`Optoelectronic devices such as lasers, photocliodes and other photodetectors,
`
`have become wider used in the telecommunications and other industries.
`
`In
`
`optoelectronic devices, an electrical signal
`
`is converted to an optical signal that
`
`travels along an optical transmission medium such as an optical fiber, and is then
`
`converted back to an electrical signal. A high optical coupling efficiency Is required
`
`to ensure good optoelectronic connections between the light source and the optical
`
`transmission medium, as well as between the optical transmission medium and the
`
`photodetector which detects the optical signal and converts the optical signal to an
`
`electrical signal.
`
`In fiber—coupled packaging, laser light, which propagates through an optical
`
`used, an air gap between the optical fiber and lens as well as between the lens and
`
`photodetector. The optical performance, or coupling efficiency, is limited by light loss
`
`due to reflection at the air/fiber, air/lens and ain’photodetector interfaces. These
`
`effects are especially significant in 2.540 Gb/s (gigabits per second) applications
`
`because of the smaller active areas of photodetectors used in such applications.
`
`This makes it increasingly difficult to attain high optical performance or high optical
`
`coupling efficiencies in 2.5-10 Gb/s applications and,
`
`in turn, adversely affects the
`
`It would therefore be desirable to provide an optical
`subsequent HF performance.
`fiber coupled to a photodetector in which light loss due to reflection is eliminated or
`
`minimized.
`
`Previous attempts to address this issue include the use of various
`
`different lens types to improve focusing. This approach is limited by package size
`
`and the space available for positioning such a lens, especially in packages of
`
`reduced size such as used for high-speed applications. Furthermore, this approach
`
`does not address the loss in optical coupling efficiency due to light reflection at the
`
`002
`
`FITBIT, Ex. 1015
`
`
`
`W0 2005f036212
`
`PCTIUSZUOSIUZS l 62
`
`In direct fiber coupling packaging, previous attempts to improve optical
`
`coupling efficiency include cleaving the optical fiber at an angle with respect to the
`
`photodetector,
`
`the angle selected to minimize back reflection. Another approach
`
`was tilting the photodetector at an angle with respect to the primary direction of the
`
`light beam being detected. Changing the cleave angle, however, only changes the
`
`direction of reflection to avoid laser light being directed back to the source. The loss
`
`of light still exists due to reflection at the interfaces between the angled end face of
`
`the optical fiber and air, as well as at the interface between the photodetector and
`
`air. Reflection also still exists when the photodetector is tilted and therefore the loss
`
`of light and reduced opticai coupling efficiency still exists.
`
`It would therefore be desirable to couple an optical transmission medium such
`
`as an optical fiber, to a photodetector. such that the amount of light lost between the
`
`optical fiber and photodetector is minimized or eliminated.
`
`SUMMARY OF THE lNVENTION
`
`_2_
`
`medium to the photodetector when light propagates in the optical transmission
`medium.
`
`To address these and other needs, and in view of its purposes, the present
`
`invention provides
`
`an optical
`
`subassembly apparatus
`
`in which an optical
`
`transmission medium is optically coupled to a photodetector in an optical coupling
`
`region and an optical thick film is formed between the optical transmission medium
`
`and the photodetector in the optical coupling region.
`
`One aspect of
`
`the invention is an apparatus comprising an optical
`
`transmission medium optically coupled to a photodetector in an optical coupling
`
`region and an optical thick film disposed on the photodetector in the optical coupling
`
`region. The optical thick film has a thick film refractive index that lies between the
`
`refractive index of air and the refractive index of the photodetector.
`
`Another aspect of
`
`the invention is an apparatus comprising an optical
`
`transmission medium optically coupled to a photodetector in an optical coupling
`
`region and a discrete optical thick film formed on the photodetector. The discrete
`
`optical thick film increases the amount of light coupled from the optical transmission
`
`A further aspect of the invention is an apparatus comprising an optical
`
`transmission medium optically coupled to a photodetector in an optical coupling
`
`region that includes a smooth surface of the optical transmission medium, the optical
`
`thick film coating interposed between the smooth surface and the photodetector.
`
`Another aspect of the present invention is a method for increasing optical
`
`coupling efficiency between an optical fiber and a photodetector. The method
`
`comprises providing an optical fiber and a photodetector, optically coupling the
`
`003
`
`FITBIT, Ex. 1015
`
`
`
`W0 2005f036212
`
`PCTIUSZUOSIUZS l 62
`
`coating on the photodetector in the optical coupling region. The coating has a
`
`coating refractive index that lies between a first refractive index of air and a Second
`
`refractive index of the photodetector surface upon which the coating is disposed.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The present
`
`invention is best understood from the following detailed
`
`description, when read in conjunction with the accompanying drawings.
`
`It
`
`is
`
`emphasized that, according to common practice, the various features of the drawing
`
`are not necessarily to scale. On the contrary, the dimensions of the various features
`
`are arbitrarily expanded or reduced for clarity and to emphasize features of the
`
`present invention. Like numerals refer to like features throughout the specification
`
`and drawings.
`
`Included are the following figures:
`
`FIGS. 1A-1C are side views showing exemplary photodetectors:
`
`FIG. 1A
`
`shows an exemplary front illumination photodetector and FIGS. 13 and 10 show
`
`exemplary back illumination photodetectors;
`
`FIG. 2 is a side view showing an optical fiber coupled to a photodetector
`
`optical fiber to the photodetector in an optical coupling region and disposing a
`
`-3-
`
`according to the PRIOR ART;
`
`FIGS. 3A and BB show exemplary embodiments of the optical
`
`thick film
`
`formed between an optical fiber and a photodetector according to the present
`
`invention: FIG. 3A is a direct coupled arrangement and FIG. 3B includes a lens;
`
`FIGS. 4A and 4B show another exemplary embodiment of the optical thick
`
`film formed between an optical fiber and a photodetector according to the present
`
`invention; and
`
`FIG. 5 shows still another exemplary embodiment of the optical matching
`
`coating formed between an optical fiber and a photodetector according to the
`
`present invention.
`
`DETAILED DESCRIPTION
`
`An aspect of the invention provides an optical thick film that is introduced to
`
`the airlphotodetector interface to improve optical coupling efficiency by reducing light
`
`loss due to reflection at the air/photodetector interface. The present invention finds
`
`application both in optical couplings that utilize a lens and in direct fiber coupled
`
`applications. The present invention finds application in high speed systems such as
`
`systems using frequencies of 2.5 Gb/s or greater.
`
`Figures 1A - 10 shows photodetectors commonly used in the fiber optic
`
`telecommunication industry.
`
`FIG. 1A shows an exemplary front
`
`illumination
`
`photodetector and FIGS. 18 and 10 show back illumination photodetectors.
`
`In each
`
`004
`
`FITBIT, Ex. 1015
`
`
`
`WO 2005036212
`
`PCTIU820031028162
`
`embodiment, photodetector 7 is disposed on base substrate 1 and includes active
`
`area 5. Facing surface 11 is defined as the photodefector surface upon which the
`
`incoming light is impingent. AS such, in each of the embodiments of FIGS. 1A-1C,
`
`-4-
`
`light will be directed to the photodetector from above photodetector 7. Photodetector
`
`7 may be a semiconductor substrate with active area 5 being formed in or on the
`
`substrate. FIG. 13 shows a back illumination photodetector 7 with a facing surface
`
`11 shaped into a microlens. Photodetector 7 may be formed of silicon or it may be
`
`formed of group Ill or IV semiconductor materials such as lnP, GaAs or Ge,
`
`particularly for high speed applications. Silicon has a refractive index of about 3.3
`
`and the materials used to form photodetectcr 7 in other embodiments, such as lnP,
`
`GaAs and Ge, may include refractive indexes that range from 3.0 to 3.5. FIGS. 1A -
`
`10 are intended to be exemplary, and not
`
`restrictive, of commonly used
`
`photodetectors which may be used in the present invention. According to other
`
`embodiments, the photodetectors may be formed of different materials and include
`
`different configurations.
`
`FIG. 2 shows an exemplary PRIOR ART arrangement of an optical
`
`transmission medium optically coupled to an exemplary front
`
`illumination
`
`photodetector in an optical coupling region. The optical transmission medium may
`
`be an optical fiber such as optical fiber 15 having and face 3. End face Sis obliquely
`
`angted with respect to facing surface 11 of active area 5 of photodetector 7 in the
`
`illustrated embodiment. Between optical fiber 15 and photodetector 7 in the optical
`
`coupling region is a gap of air 9. As such, facing surface 11 of active area 5 of
`
`photodetector 7 forms an interface with air 9, i.e., the airfphotcdetector interface.
`
`In
`
`other exemplary embodiments in which a back illumination photodetector is used,
`
`facing surface 11 may be the surface of the photodetector that is opposite the
`
`surface inciuding active area 5. Light propagation direction 17 is generally along the
`
`core of optical fiber 15.
`
`FIG. 3A shows an exemplary embodiment of an optical subassembly of the
`
`present invention. The optical coupling apparatus of the optical subassembiy
`
`includes an optical transmission medium,
`
`i.e., optical fiber 15 in the exemplary
`
`embodiment. Optical fiber 15 and photodetector 7 are optically coupled in an optical
`
`coupling region that includes facing surface 11. The optical coupling region refers to
`
`the region in which light from one component, such as optical fiber 15, is coupled to
`
`or travels to another component, such as photodetector 7 including active area 5.
`
`Optical fiber 15 may be coupled to photodetector 7 in a hermetic or non-hermetic
`
`package. Active area 5 is located within the optical coupling region, and along the
`
`optical path of light. Light propagation direction 17 is generally along the core of
`
`optical fiber 15. Various well known techniques and mechanical means may be used
`
`005
`
`FITBIT, Ex. 1015
`
`
`
`W0 200511036212
`
`PCTIU820031028162
`
`to secure optical fiber 15 in fixed position with respect to photodetector 7. Epoxy,
`
`solder and other materials may be used.
`
`In various exemplary embodiments, optical
`
`fiber 15 may be retained by an optical ferrule, not shown in FIG. 3A.
`
`In the
`
`exemplary embodiment shown in FIG. 3A, light propagates along light propagation
`
`-5-
`
`direction 17 which is generally along the longitudinal direction of optical fiber 15 and
`
`a light beam exits optical fiber 15 at end face 3 and is delivered along light beam
`
`delivery direction 27 towards active area 5 of photodetector 7. End face 3 may be
`
`poiished and smooth in an exemplary embodiment. For example, end face 3 may be
`
`poiished to include a surface roughness Ra no greater than 0.1 microns, but other
`
`surfaces may be used in other exemplary embodiments. Furthermore,
`
`the non-
`
`parallel relationship between end surface 3 and facing surface 11 is intended to be
`
`exemplary only.
`
`In other exemplary embodiments, end face 3 may be substantially
`
`parallel
`
`to facing surface 11 of active area 5 of photodetector 7, or the angles
`
`between and face 3 and facing surface 11 may vary from the illustrated relationship
`
`which may represent an angular variation of 7 to 9 degrees.
`
`In the exemplary front illumination embodiment illustrated in FIG. 3A, facing
`
`surface 11 includes a surface of active area 5.
`
`In other exemplary embodiments
`
`such as back illumination embodiments, facing surface 11 may be the surface of
`
`photodetector 7 that is opposite active area 5. Facing surface 11 of photodetector 7
`
`is coated with optical thick film 13 in the illustrated embodiment of FIG. 3A. The
`
`airi'photodetector interface shown in FIG. 2 (the prior art) is now replaced by optical
`
`thick film 13 in the exemplary embodiment of FIG. 3A. A gap of air 9 exists between
`
`optical thick film 13 and end face 3 of optical fiber 15.
`
`FIG. 38 shows another exemplary embodiment of optical thick film 13 formed
`
`in the optical coupling region on facing surface 11 of active area 5 of photodetector
`
`7. Lens 23 is disposed within the gap of air 9 formed between Optical fiber 15 and
`
`photodetector 7 in the optical coupling region and helps direct light from optical fiber
`
`to photodetector 7. Lens 23 may be formed of glass, quartz, sapphire or other
`
`suitable materials, and lens 23 may be secureiy positioned with respect to optical
`
`fiber 15 and photodetector 7 using various conventional means.
`
`Optical fiber 15 may be any of various suitable optical fibers available in the
`
`art. Single mode or muitimode optical fibers may be used.
`
`In other exemplary
`
`embodiments, optical fiber 15 may be replaced by other suitable optical transmission
`
`media.
`
`Photodetector 7 may be a PIN photodetector or various other suitable
`
`photodiodes or other photodetectors available in the art. The size of active area 5
`
`and the materials used to form active area 5 will vary depending on application in
`
`various exemplary embodiments. The size of optical fiber 15 may also vary in the
`
`various exemplary embodiments. The relative position of optical fiber 15 and
`
`006
`
`FITBIT, Ex. 1015
`
`
`
`W0 200511036212
`
`PCTIU820031028162
`
`photodetector 7, as well as the spacing between these components, and the choice
`
`of a front or back illuminator photodetector will vary depending upon application.
`Various suitable arrangements of the components may be used.
`_
`
`FIGS. 13 and 1C), optical thick film 13 will have a refractive index that lies between
`
`The light propagating along primary propagation direction 17 of optical fiber
`
`15 is provided by light source 21 shown in FIG 3A. Light source 21 may be a laser,
`
`such as a VCSEL (vertical cavity surface emitting laser), but other lasers and other
`
`optical sources may be used in other exemplary embodiments. The light produced
`
`by such an optical source, propagating along optical fiber 15 and which exits optical
`
`fiber 15 at light deiivery location 19 on end face 3 and along light beam delivery
`
`direction 27, is detected by photodetector 7 and converted to an electronic signal by
`
`photodetector 7 in conjunction with conventional electronic circuitry (not shown).
`
`Light of various wavelengths may be used. According to various exemplary
`
`embodiments,
`
`light having a wavelength of 1310 nanometers or 1550 nanometers
`
`may be used, but light having other wavelengths may be used in other exemplary
`
`embodiments.
`
`The
`
`present
`
`invention
`
`finds
`
`application
`
`in
`
`high-speed
`
`telecommunications systems such as telecommunications systems operating at
`
`frequencies of 2.5-10 bes and higher.
`Various conventional methods may be suitably used to form optical thick film
`
`13 on photodetector 7 along the optical path,
`
`i.e., on facing surface 11
`
`in the
`
`exemplary embodiments illustrated in FIGS. 3A and 3(3). For example, a syringe
`
`such as with micro-dispensing capabilities may be used to apply optical thick film 13.
`
`Optical thick film 13 is placed between an incident medium, for example, air 9,
`
`and a transmitted medium, for example, photodetector 7 or, more particularly, any
`
`film or coating formed on facing surface 11 of photodetector 7. Optical thick film 13
`
`is preferably chosen to be transparent with minimum absorption at the working
`
`wavelength. Optical thick film 13 includes a refractive index that is between the
`
`respective refractive indices of the incident medium and the transmitted medium that
`
`form the interface upon which the optical thick film is disposed. For example, optical
`
`thick film 13 formed on the air/photodetector interface between air 9 of photodetector
`
`7, is chosen to have a refractive index that lies between the refractive index of air 9
`
`and the refractive index of the material of which facing surface 11 of photodetector 7
`
`is formed.
`
`it facing surface 11 includes the facing surface of active area 5 as in the
`
`illustrated front illumination embodiment, optical thick film 13 will have a refractive
`index that lies between the refractive index of air and the refractive index of the
`
`material of which the active area 5 surface is formed, more particularly, the refractive
`
`index of the upper layer of active area 5.
`
`In back illumination embodiments (see
`
`007
`
`FITBIT, Ex. 1015
`
`
`
`W0 2005f036212
`
`PCTIUSZUOSIUZS l 62
`
`the refractive index of air and the refractive index of the material which forms facing
`
`surface 11 of photodetector 7, which is opposite the surface containing active area 5.
`
`Without the optical
`
`thick film of the present
`
`invention,
`
`the reflectance of
`
`normal incidence for a single interface formed between an incident medium and a
`
`2
`
`n, a n,
`
`R _ [Rf + “1]
`
`.
`
`(Equation #1)
`
`where H = reflectance
`
`Hi: refractive index of incident medium
`
`n, = refractive index of transmitted medium
`
`When an optical matching coating such as optical thick film 13 that includes a
`
`refractive index of no, is added to the lncidenb’transmitted interface, the total
`
`reflectance for the first order of approximation can be expressed as follows:
`
`2
`
`2
`
`no .- n]
`
`I
`
`(EQUatIon #2)
`
`transmitted medium is determined according to Fresnel's Law and expressed as
`follows:
`
`ranging from 1.8 to 2.2 may be used.
`
`H
`
`n,- "‘ no
`
`RT _ [31, + no] + [ no + “1]
`
`where:
`
`Fir -- total reflectance
`
`no —— refractive index of the optical matching coating
`
`If the n,- < no< ni, we have
`
`3]" < H
`
`In an exemplary embodiment, optical fiber 15 may include a refractive index
`
`within the range of 1.4 to 1.5, or more particularly, within the range of 1.43 to 1.46,
`
`but optical fibers having other refractive indices may be used in other exemplary
`
`embodiments. Air 9 is typically assigned a refractive index of approximately 1.0.
`
`The relevant refractive index of photodetector 7 is determined by the material of
`
`which the upper facing surface 11 of photodetector 7 is formed. As such, in the front
`
`illumination embodiments such as illustrated, the relevant refractive index is the
`
`refractive index of the material that forms the upper surface of active area 5 that
`
`forms part of facing surface 11.
`
`In one exemplary embodiment,
`
`the relevant
`
`refractive index may be about 2.2.
`
`In an exemplary embodiment, the upper facing
`
`surface of active area 5, i.e., of facing surface 11, may be formed of silicon nitride,
`
`but other materials may be used in other exemplary embodiments. For example,
`
`materials having refractive indexes
`
`008
`
`FITBIT, Ex. 1015
`
`
`
`WO 2005036212
`
`PCTIU820031028162
`
`Photodetectors having facing surfaces with various other refractive indices may be
`
`used in other exemplary embodiments.
`
`-3-
`
`optical fiber 15 and photodetector 7 in the optical coupling region, as will be shown in
`FIGS. 43 and 5.
`
`According to the back illumination exemplary embodiments shown in FIGS.
`
`18 and 10, facing surface 11 of photodetector 7 may be a silicon nitride or similar
`
`film having a refractive index within the range of 1.8 to 2.2.
`
`In yet another exemplary
`
`embodiment of the back illumination arrangement such a film may not be used and
`
`the relevant refractive index of facing surface 11 is the refractive index of the
`
`material of which photodetector 7 is formed.
`
`In such back illumination embodiments
`
`as well as in the illustrated front illumination embodiment of FIGS. 3A and 33, facing
`
`surface 11 is coated with optical thick film 13.
`
`In an exemplary embodiment, optical thick film 13 may include a refractive
`
`index of 1.40.
`
`In an exemplary embodiment, optical thick fiim 13 may be silicone.
`
`In
`
`other exemplary embodiments, optical thick film 13 may be formed of other materials
`
`that have refractive indexes that preferably lie between the refractive indices of the
`
`respective materials which form the interface upon which the optical thick film is
`
`formed. For example, optical thick film 13 may include a refractive index within the
`
`range of 1.37 - 1.45. The application portion and shape of optical thick film 13 may
`
`vary in different exemplary embodiments. Optical thick film 13 may be a layer of
`
`material formed over the component surface. Optical thick film 13 may include a
`
`thickness 15 which lies within the range of 10-30 microns according to one
`
`exemplary embodiment. but other thicknesses may be used in other exemplary
`
`embodiments. For example, optical thick film 13 may extend continuously between
`
`Applicants have discovered that optical thick film 13 also reduces light loss by
`
`divergence of the light delivered by optical fiber 15 to photodetector 7.
`
`In prior art
`
`arrangements not using the optical coating 13 medium of the present invention,
`
`divergence of a light beam emanating from an optical fiber core is significant when
`
`extremely small beam diameters and light having long wavelengths is used. This, in
`
`turn,
`
`results in light
`
`loss and lower coupling efficiency, especially in 10 bes
`
`photodetector coupling applications. Furthermore, application of the optical thick film
`
`improves the irradiance profile of light at the photodetector, i.e., light is distributed
`
`more evenly with the use of the optical thick film.
`
`FIGS. 4A and 4B shows further exemplary embodiments of an optical
`
`coupling arrangement that employs optical thick film 13 according to the present
`
`invention.
`
`In FIGS. 4A and 4B,
`
`the longitudinal direction of optical fiber 15 is
`
`generally orthogonal to facing surface 11 of photodetector 7. End face 3' is angled
`
`and polished so that light propagating through optical fiber 15 along light propagation
`
`009
`
`FITBIT, Ex. 1015
`
`
`
`WO 2005036212
`
`PCTIU820031028162
`
`direction 17, internally reflects off polished end face 3‘ and exits optical fiber 15 at
`
`light delivery location 19 and along light beam delivery direction 27, which is
`
`generally orthogonal to the longitudinal direction of optical fiber 15. Light delivery
`
`location 19 is formed on a sidewall of optical fiber 15. Such sidewalls are generally
`
`smooth surfaces.
`
`in one exemplary embodiment,
`
`the sidewalls may include a
`
`surface roughness Fla of less than 0.1 microns.
`
`In FIG. 4A, facing surface 11 is
`
`coated with optical thick film 13 as described above.
`
`FIG. 4B is an exemplary embodiment of an optical coupling arrangement
`
`similar to the embodiment shown in HS. 4A, but
`
`in which optical
`
`thick film 13
`
`extends continuously from facing surface 11 of active area 5 of photodetectcr 7, to
`
`light delivery location 19 of optical fiber 15 in the optical coupling region. According
`
`to this exemplary embodiment, an air gap is not present between optical fiber 15 and
`
`photodetectcr 7 along the optical path. in this exemplary embodiment, the present
`
`media is reduced resulting in reduced reflectance at the optical fiber/optical thick film
`
`and photodetectcr/optical
`
`thick film interfaces. compared to optical
`
`fiben’air and
`
`photodetectorlair interfaces, as according to Equation #1. The refractive index of
`
`optical thick film 13 may be at least one of between the refractive index of air and the
`
`refractive index of the optical fiber, and between the refractive index of air and the -
`
`refractive index of facing surface 11 of photodetectcr 7. The arrangement shown in
`
`FIG. 4(B) is exemplary only and in other exemplary embodiments the optical thick
`
`film may extend continuously between an end face of an optical
`
`fiber and
`
`photodetectcr surface in the optical coupling region. Furthermore, the photodetector
`
`used in the sidewatl emitting configuration shown in FIGS. 4A and 48 may be a back
`
`illumination photodetectcr.
`
`invention provides that the refractive index of optical thick film 13 is higher than that
`of air so the difference between refractive indexes of the incident and transmitted
`
`embodiments. The photodetectcr with the optical thick film, therefore, may be used
`
`FIG. 5 shows an exemplary embodiment of an arrangement of optical fiber 15
`
`coupled to photodetectcr 7 which is a back illumination photodetectcr and includes
`
`active area 5 disposed in the optical coupling region and along the optical path.
`
`Facing surface 11 is the surface of photodetectcr 7 opposite the surface upon which
`
`active area 5 is formed.
`
`in the exemplary embodiment illustrated in FIG 5, facing
`
`surface 11 of back iltumination photodetectcr 7 is shaped into a microlens, and
`
`optical
`
`thick film 13 extends continuously between facing surface 11 and light
`
`delivery location 19.
`
`The optical
`
`thick film disposed on the surface of photodetectcr may
`
`additionally provide hermetical protection of the photodetector in various exemplary
`
`010
`
`FITBIT, Ex. 1015
`
`
`
`WO 2005036212
`
`PCTIU820031028162
`
`in non-hermetic packages, as well as hermetic packages in which the gap formed
`
`between optical fiber 15 and photodetector 7 may be a vacuum or other media.
`
`The preceding merely illustrates the principles of the invention.
`
`it will thus be
`
`which, although not explicitly described or shown herein, embody the principles of
`
`the invention and are included within its scope and spirit. For example, the principles
`
`of the present invention may be applied to arrays of photodetectors.
`
`Furthermore,
`
`all examples and conditional
`
`language recited herein are
`
`principally intended expressly to be only for pedagogical purposes and to aid in
`
`understanding the principles of the invention and the concepts contributed by the
`
`inventors to furthering the art, and are to be construed as being without limitation to
`
`such specifically recited examples and conditions. Moreover, all statements herein
`
`reciting principles, aspects, and embodiments of the invention, as well as specific
`
`examples thereof, are intended to encompass both structural and the functional
`
`equivalents thereof. Additionally,
`
`it is intended that such equivalents include both
`
`currently known equivalents and equivalents developed in the future,
`
`i.e., any
`
`elements developed that perform the same function, regardless of structure. The
`
`scope of the present
`
`invention,
`
`therefore, is not
`
`intended to be limited to the
`
`exemplary embodiments shown and described herein. Rather, the scope and spirit
`
`appreciated that those skilled in the art will be able to devise various arrangements
`
`of the present invention is embodied by the appended claims and their equivalents.
`
`011
`
`FITBIT, Ex. 1015
`
`
`
`WO 2005036212
`
`PCTIU820031028162
`
`WHAT IS CLAIMED IS:
`
`1.
`
`An apparatus comprising an optical
`
`transmission medium optically
`
`coupled to a photodetector in an optical coupling region and an optical thick film
`
`said photcdetector.
`
`2.
`
`The apparatus as in claim 1, wherein said photodetector includes an
`
`active area and said optical transmission medium includes a light delivery location
`
`where light exits said optical transmission medium. said optical coupling region
`
`including said active area and said light delivery location.
`
`3.
`
`The apparatus as in claim 1, wherein said second refractive index
`
`comprises a refractive index of material
`
`that forms a facing surface of said
`
`photodetector in said optical coupling region.
`
`4.
`
`The apparatus as in claim 3, wherein said material comprises silicon
`
`nitride.
`
`5.
`
`The apparatus as in claim 3. wherein said facing surface includes a
`
`surface of an active area of said photodetector.
`
`disposed on said photodetector in said optical coupling region and having a thick film
`refractive index between a first refractive index of air and a second refractive index of
`
`comprises an optical fiber.
`
`6.
`
`The apparatus as in claim 3, wherein said photodetector comprises a
`
`substrate with an active area on a first surface of said substrate and along an optical
`
`path of light coupled from said optical transmission medium to said photodetector,
`
`and said facing surface is an opposed surface of said substrate.
`
`7.
`
`The apparatus as in claim 1, wherein said optical transmission medium
`
`has a smooth end face and said optical thick film extends continuously between said
`
`smooth end face and said photodetector.
`
`8.
`
`The apparatus as in claim 1, further comprising an optical source that
`
`causes light having a wavelenth of one of 1310nm and 1550nm to propagate through
`
`said optical transmission medium.
`
`9.
`
`The apparatus as in claim 1 wherein said optical transmission medium
`
`012
`
`FITBIT, Ex. 1015
`
`
`
`WO 2005036212
`
`PCTIU820031028162
`
`10.
`
`The apparatus as in claim 9, wherein light exits said optical fiber at an
`
`end face of said optical fiber.
`
`11.
`
`The apparatus
Accessing this document will incur an additional charge of $.
After purchase, you can access this document again without charge.
Accept $ ChargeStill Working On It
This document is taking longer than usual to download. This can happen if we need to contact the court directly to obtain the document and their servers are running slowly.
Give it another minute or two to complete, and then try the refresh button.
A few More Minutes ... Still Working
It can take up to 5 minutes for us to download a document if the court servers are running slowly.
Thank you for your continued patience.
This document could not be displayed.
We could not find this document within its docket. Please go back to the docket page and check the link. If that does not work, go back to the docket and refresh it to pull the newest information.
Your account does not support viewing this document.
You need a Paid Account to view this document. Click here to change your account type.
Your account does not support viewing this document.
Set your membership
status to view this document.
With a Docket Alarm membership, you'll
get a whole lot more, including:
- Up-to-date information for this case.
- Email alerts whenever there is an update.
- Full text search for other cases.
- Get email alerts whenever a new case matches your search.
One Moment Please
The filing “” is large (MB) and is being downloaded.
Please refresh this page in a few minutes to see if the filing has been downloaded. The filing will also be emailed to you when the download completes.
Your document is on its way!
If you do not receive the document in five minutes, contact support at support@docketalarm.com.
Sealed Document
We are unable to display this document, it may be under a court ordered seal.
If you have proper credentials to access the file, you may proceed directly to the court's system using your government issued username and password.
Access Government Site