# US 5,703,977 A · Integrated optical mode converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,977 A - Document ID: US5703977A - Status: Granted - Kind: A - Application number: 08/659,117 - Filed: 1996-06-04 - Granted: 1997-12-30 - Earliest claimed: 1995-07-07 - Assignees: Koninklijke PTT Nederland N.V. - Inventors: J.o slashed.rgen Werngreen Pedersen - Web page: https://patentgrep.com/patent/US5703977A ## CPC - G02B 6/136: by etching - G02B 6/126: using polarisation effects {(G02B6/1226 takes precedence)} - G02B 6/14: Mode converters - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract Integrated optical mode converter provided with a channel-shaped waveguide comprising a periodic concatenation of two wave-guiding subsections (P) and (Q) defined by a strip-shaped structure supported by a substrate. The waveguide profiles of the subsections (P) and (Q) are defined by two different partial strips, of which at least one is, but preferably both are, provided with a slot (S.sub.P, S.sub.Q) running in a longitudinal direction of the partial strip in question. The slots have been applied in such a manner that only the field distribution of one of the two guided modes involved in the mode conversion is affected. The resulting structure has increased conversion per interface; and lower attenuation in specific embodiments. ## Claims ### Claim 1 An integrated optical mode converter for converting a fraction of a signal component of a light signal propagating according to a first guided mode into a signal component propagating according to a second guided mode, with one of the two guided modes having an even order number and the other of the two guided modes having an odd order number, said integrated optical mode converter comprising: a channel-shaped waveguide supported by a substrate, in which a periodic coupling takes place between the two guided modes of the light signal propagating in the waveguide, said waveguide comprising an incoming wave-guiding section, an intermediary wave-guiding section and an outgoing wave-guiding section, and said intermediary wave-guiding section comprising a periodic concatenation of two wave-guiding subsections per period, a length of the two wave-guiding subsections and a number of periods thereof being tuned to a desired fraction of conversion, wherein at least one of the two wave-guiding subsections has a waveguide profile including a partial profile which has a deforming effect on a field distribution of one of the two guided modes and which does not substantially affect a field distribution of the other one of the two guided modes. ### Claim 2 (depends on 1) The mode converter according to claim 1, wherein each of the two wave-guiding subsections has a waveguide profile which is substantially determined by a strip-shaped element having said partial profile, said strip-shaped element being provided with a slot running according to a longitudinal direction of the strip-shaped element of each of the two wave-guiding subsections. ### Claim 3 (depends on 1) The mode converter according to claim 1, wherein each of the two wave-guiding subsections has a waveguide profile including said partial profile, said waveguide profile being determined by a strip-shaped element provided with a slot running according to a longitudinal direction of the strip-shaped element of each of the two wave-guiding subsections. ### Claim 4 (depends on 3) The mode converter according to claim 3, wherein the strip-shaped elements connect to one another with an offset, and the slots thereof are in line. ### Claim 5 (depends on 3) The mode converter according to claim 3, wherein the strip-shaped elements are in line, and the slots thereof have an offset with respect to one another. ### Claim 6 (depends on 2) The mode converter according to claim 2, wherein the slots have a substantially rectangular transverse section. ### Claim 7 (depends on 2) The mode converter according to claim 2, wherein the slots have a substantially trapezium-shaped transverse section. ### Claim 8 (depends on 2) The mode converter according to claim 2, wherein the slots have a substantially triangular transverse section. ### Claim 9 (depends on 3) The mode converter according to claim 3, wherein the slots have different transverse sections. ### Claim 10 (depends on 3) The mode converter according to claim 3, wherein the strip-shaped elements mutually differ in transverse section, and the slots have mutually equal transverse sections and are in line. ### Claim 11 (depends on 3) The mode converter according to claim 3, wherein the strip-shaped elements have mutually equal transverse sections and are in line, and the slots have mutually different transverse sections. ### Claim 12 (depends on 1) The mode converter according to claim 1, wherein each of the two wave-guiding subsections is bimodal. ### Claim 13 A method for manufacturing a channel-shaped waveguide on a substrate comprising a package of layers having a light-conducting layer, said waveguide comprising a concatenation of wave-guiding sections alternating with a first and a second waveguide profile substantially defined by strip-shaped elements of a first and a second type, respectively, with the strip-shaped elements of at least one of the two types being provided with a slot running in a longitudinal direction thereof, the method comprising the following steps: (a) applying to the substrate a first mask pattern of a first mask material, said first mask pattern comprising mask parts corresponding to the strip-shaped elements of the first and the second type, and to the slots running in the strip-shaped elements of at least one of the two types, (b) etching, in a first etching operation, parts of the substrate not covered by any mask material, (c) covering up mask parts of the first mask pattern, which correspond to the slots running in the strip-shaped elements of at least one of the two types, with a second mask pattern of a second material, (d) etching, in a second etching operation, parts of the substrate not covered by any mask material. ### Claim 14 (depends on 13) The method according to claim 13, wherein the first and second etching operations are carried out with a same etching agent, with the parts of the substrate not covered by any mask material being etched in the first etching operation to a first etching depth, and in the second etching operation to a second etching depth. ### Claim 15 (depends on 13) The method according to claim 13, wherein, in a first intermediary step of the steps (a) and (b), an auxiliary-mask pattern of a further mask material is applied for covering the mask parts of the first mask pattern, which correspond to the strip-shaped elements of the first and of the second type, and for leaving uncovered the mask parts of the first mask pattern, which correspond to the slots running in the strip-shaped elements of at least one of the two types, and wherein, in a second intermediary step of the steps (b) and (c), the further mask material of the auxiliary-mask pattern is removed. ### Claim 16 (depends on 15) The method according to claim 15, wherein the strip-shaped elements of the two types are provided with a slot running in a longitudinal direction thereof, and wherein the first etching operation of the step (b) comprises the following substeps: (b1) applying a first partial-mask pattern of a third mask material for covering mask parts of the first mask pattern, which correspond to the slots in the strip-shaped elements of the first type, (b2) etching, in a first partial-etching step, parts of the substrate not covered by any mask material, (b3) removing the first partial-mask pattern, (b4) applying a second partial-mask pattern of the third mask material for covering mask parts of the first mask pattern, which correspond to the slots in the strip-shaped elements of the second type, (b5) etching, in a second partial-etching step, parts of the substrate not covered by any mask material. ### Claim 17 (depends on 13) A channel-shaped waveguide manufactured in accordance with the method of claim 13, wherein said channel-shaped waveguide is provided on a substrate comprising a package of layers having a light-conducting layer, said waveguide comprises a concatenation of wave-guiding sections alternating with a first and a second waveguide profile substantially defined by strip-shaped elements, and at least one of said strip-shaped elements is provided with a slot running in a longitudinal direction thereof so that at least one of the wave-guiding subsections has a waveguide profile including a partial profile which has a deforming effect on a field distribution of one of two guided modes of a propagated light signal and which does not substantially affect a field distribution of the other one of the two guided modes. ### Claim 18 (depends on 3) The mode converter according to claim 3, wherein the slots have a substantially rectangular transverse section. ### Claim 19 (depends on 4) The mode converter according to claim 4, wherein the slots have a substantially rectangular transverse section. ### Claim 20 (depends on 5) The mode converter according to claim 5, wherein the slots have a substantially rectangular transverse section. ### Claim 21 (depends on 3) The mode converter according to claim 3, wherein the slots have a substantially trapezium-shaped transverse section. ### Claim 22 (depends on 4) The mode converter according to claim 4, wherein the slots have a substantially trapezium-shaped transverse section. ### Claim 23 (depends on 5) The mode converter according to claim 5, wherein the slots have a substantially trapezium-shaped transverse section. ### Claim 24 (depends on 3) The mode converter according to claim 3, wherein the slots have a substantially triangular transverse section. ### Claim 25 (depends on 4) The mode converter according to claim 4, wherein the slots have a substantially triangular transverse section. ### Claim 26 (depends on 5) The mode converter according to claim 5, wherein the slots have a substantially triangular transverse section. ### Claim 27 (depends on 4) The mode converter according to claim 4, wherein the slots have different transverse sections. ### Claim 28 (depends on 5) The mode converter according to claim 5, wherein the slots have different transverse sections. ### Claim 29 (depends on 14) A channel-shaped waveguide manufactured in accordance with the method of claim 14, wherein said channel-shaped waveguide is provided on a substrate comprising a package of layers having a light-conducting layer, said waveguide comprises a concatenation of wave-guiding sections alternating with a first and a second waveguide profile substantially defined by strip-shaped elements, and at least one of said strip-shaped elements is provided with a slot running in a longitudinal direction thereof so that at least one of the wave-guiding subsections has a waveguide profile including a partial profile which has a deforming effect on a field distribution of one of two guided modes of a propagated light signal and which does not substantially affect a field distribution of the other one of the two guided modes. ### Claim 30 (depends on 15) A channel-shaped waveguide manufactured in accordance with the method of claim 15, wherein said channel-shaped waveguide is provided on a substrate comprising a package of layers having a light-conducting layer, said waveguide comprises a concatenation of wave-guiding sections alternating with a first and a second waveguide profile substantially defined by strip-shaped elements, and at least one of said strip-shaped elements is provided with a slot running in a longitudinal direction thereof so that at least one of the wave-guiding subsections has a waveguide profile including a partial profile which has a deforming effect on a field distribution of one of two guided modes of a propagated light signal and which does not substantially affect a field distribution of the other one of the two guided modes. ### Claim 31 (depends on 16) A channel-shaped waveguide manufactured in accordance with the method of claim 16, wherein said channel-shaped waveguide is provided on a substrate comprising a package of layers having a light-conducting layer, said waveguide comprises a concatenation of wave-guiding sections alternating with a first and a second waveguide profile substantially defined by strip-shaped elements, and at least one of said strip-shaped elements is provided with a slot running in a longitudinal direction thereof so that at least one of the wave-guiding subsections has a waveguide profile including a partial profile which has a deforming effect on a field distribution of one of two guided modes of a propagated light signal and which does not substantially affect a field distribution of the other one of the two guided modes.