# US 7,466,726 B2 · Fast continuously wavelength tuning single frequency fiber laser using tunable polymer optical filters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,466,726 B2 - Document ID: US7466726B2 - Status: Granted - Kind: B2 - Application number: 10/966,638 - Filed: 2004-10-14 - Published: 2005-04-14 - Granted: 2008-12-16 - Earliest claimed: 2003-10-14 - Assignees: PolarOnyx, Inc. - Inventors: Jian Liu - Web page: https://patentgrep.com/patent/US7466726B2 ## CPC - G02B 6/2746: {comprising non-reciprocal devices, e.g. isolators, FRM, circulators, quasi-isolators (magneto-optic non-reciprocal devices G02F1/093)} - G02B 6/266: {the optical element being an attenuator} - H01S 3/067: Fibre lasers - H01S 3/107: using electro-optic devices, e.g. exhibiting Pockels or Kerr effect {(H01S3/1061, H01S3/1063, H01S3/1065 take precedence)} - H01S 3/0064: {Anti-reflection devices, e.g. optical isolaters (absorbing layers for marking or protecting purposes in laser working B23K26/50; magneto-optical non-reciprocal devices G02F1/093, G02F1/0955)} - H01S 3/08031: Single-mode emission - H01S 3/083: Ring lasers {(fibre ring lasers H01S3/06791)} - H01S 3/094003: {the pumped medium being a fibre} - H01S 3/0941: of a laser diode - H01S 3/1305: {Feedback control systems} - H01S 3/137: for stabilising of frequency - H01S 3/1608: {erbium} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - 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 ## Abstract A method for generating a laser projection by employing a laser gain medium for receiving an optical input projection from a laser pump. The method further includes a step of employing a mode selection filter comprising an electro-optical (EO) tunable layer disposed between two parallel reflection plates for generating a laser of a resonant peak. ## Claims ### Claim 1 A fiber-based ring laser, comprising: a laser gain medium configured to produce a first laser beam; a mode-selection filter configured to filter the first laser beam to produce a second laser beam, wherein the mode-selection filter has a transmission spectrum that includes a plurality of transmission peaks, wherein one of the plurality of transmission peaks has a first bandwidth at a first wavelength and is separated from one of its adjacent transmission peaks by a frequency difference; a first optical fiber configured to transmit the first laser beam from the laser gain medium to the mode-selection filter; and a band-pass filter configured to filter the second laser beam and to produce a third laser beam, wherein the band-pass filter has a second bandwidth wider than the first bandwidth but narrower than the frequency difference, wherein the band-pass filter is configured to pass the one of the plurality of transmission peaks at the first wavelength while filtering out other transmission peaks in the plurality of transmission peaks in the second laser beam, wherein the laser gain medium, the first optical fiber, the mode-selection filter, and the band-pass filter in part form a ring cavity in the fiber-based ring laser; wherein the mode-selection filter comprises: a first reflective plate; a second reflective plate parallel to the first reflective plate; and an electro-optical material disposed between the first parallel reflective plate and the second reflective plate. ### Claim 2 (depends on 1) The fiber-based ring laser of claim 1, wherein the mode-selection filter further comprises means for applying an electric field in the electro-optical material to vary the first wavelength at which the one of the plurality of transmission peaks is located. ### Claim 3 (depends on 2) The fiber-based ring laser of claim 2, wherein the electric field is substantially parallel to the first reflective plate. ### Claim 4 (depends on 2) The fiber-based ring laser of claim 2, wherein the means for applying an electric field comprises two electrodes configured to apply an electric voltage across the electro-optical material. ### Claim 5 (depends on 4) The fiber-based ring laser of claim 4, wherein the electric field in the electro-optical material is configured to vary the first wavelength by more than 40 pm for each voltage applied across the electro-optical material. ### Claim 6 (depends on 4) The fiber-based ring laser of claim 4, wherein the electric field in the electro-optical material is configured to tune the one of the plurality of transmission peaks in a frequency range wider than 20 GHz. ### Claim 7 (depends on 2) The fiber-based ring laser of claim 2, wherein the first reflective plate and the second reflective plate are positioned substantially orthogonal to the first laser beam and the second laser beam, wherein the electric field is substantially parallel to the first reflective plate. ### Claim 8 (depends on 1) The fiber-based ring laser of claim 1, wherein the electro-optical material is selected from a group consisting of LiNbO3, a semiconductor material, a PLZT, KTN (KTaNbO3), and an electro-optical polymer. ### Claim 9 (depends on 1) The fiber-based ring laser of claim 1, wherein the plurality of transmission peaks are separated by substantially the same frequency difference. ### Claim 10 (depends on 1) The fiber-based ring laser of claim 1, further comprising: a coupler configured to output at least a portion of the third laser beam out of the ring cavity; and a second optical fiber configured to transmit the third laser beam from the band-pass filter to the coupler, wherein the coupler and the second optical fiber in part form the ring cavity in the fiber-based ring laser. ### Claim 11 (depends on 1) The fiber-based ring laser of claim 1, wherein the laser gain medium is selected from a group consisting of an erbium doped fiber (EDF), a rare earth doped fiber, a Tm doped fiber, a Telluride doped fiber, a Yb doped fiber, and an Er/Yb doped fiber. ### Claim 12 (depends on 1) The fiber-based ring laser of claim 1, further comprising a laser pump a laser gain medium configured to produce a pump laser beam, wherein the laser gain medium is configured to produce the first laser beam in response to the pump laser beam. ### Claim 13 (depends on 1) The fiber-based ring laser of claim 1, further comprising: an optical sensor configured to output an output sensing signal in response to the third laser beam; and a controller configured to control the mode-selection filter in response to the output sensing signal to reduce fluctuations in power, frequency, or a combination thereof in the third laser beam. ### Claim 14 (depends on 13) The fiber-based ring laser of claim 13, wherein the optical sensor comprises: an etalon having a free spectral range between 10 GHz and 300 GHz and configured to transmit a portion of the third laser beam to produce a first laser sensing signal, and a comparator is configured to produce the output sensing signal by comparing the third laser beam and the first laser sensing signal. ### Claim 15 (depends on 1) The fiber-based ring laser of claim 1, wherein the third laser beam has a line width narrower than 150 GHz. ### Claim 16 (depends on 15) The fiber-based ring laser of claim 15, wherein the third laser beam has a line width narrower than 1 GHz. ### Claim 17 A fiber-based ring laser, comprising: a laser gain medium configured to produce a first laser beam; a mode-selection filter comprising: a first reflective plate configured to receive the first laser beam orthogonal to the first reflective plate; an electro-optical material disposed between the first parallel reflective plate and the second reflective plate; a second reflective plate parallel to the first reflective plate, wherein the first reflective plate, the electro-optical material, and the second reflective plate are configured to filter the first laser beam to produce a second laser beam exiting the second reflection plate, wherein the second laser beam comprises a plurality of spectral peaks having first line widths, wherein two of the plurality of spectral peaks are separated by a frequency difference; and an electrode configured to apply an electric field in the electro-optical material, the electric field being substantially perpendicular to the first laser beam or the second laser beam; a first optical fiber configured to transmit the first laser beam from the laser gain medium to the mode-selection filter; and a band-pass filter configured to filter the second laser beam and to produce a third laser beam having one of the plurality of spectral peaks, wherein the laser gain medium, the first optical fiber, the mode-selection filter, and the band-pass filter in part form a ring cavity in the fiber-based ring laser. ### Claim 18 (depends on 17) The fiber-based ring laser of claim 17, wherein the electrode is configured to vary strength of the electric field to shift frequencies of the plurality of spectral peaks. ### Claim 19 (depends on 18) The fiber-based ring laser of claim 18, wherein the electric field in the electro-optical material is configured to vary wavelengths of the plurality of spectral peaks by more than 40 pm for each voltage applied across the electro-optical material. ### Claim 20 (depends on 17) The fiber-based ring laser of claim 17, wherein the electric field in the electro-optical material is configured to tune the one of the plurality of transmission peaks in a frequency range wider than 20 GHz. ### Claim 21 (depends on 17) The fiber-based ring laser of claim 17, wherein the band-pass filter has a second bandwidth wider than the first bandwidth but narrower than the frequency difference. ### Claim 22 (depends on 17) The fiber-based ring laser of claim 17, wherein the electro-optical material is selected from a group consisting of LiNbO3, a semiconductor material, a PLZT, KTN (KTaNbO3), and an electro-optical polymer. ### Claim 23 (depends on 17) The fiber-based ring laser of claim 17, wherein the plurality of spectral peaks are separated by substantially the same frequency difference. ### Claim 24 (depends on 17) The fiber-based ring laser of claim 17, wherein the third laser beam has a line width narrower than 150 GHz. ### Claim 25 (depends on 24) The fiber-based ring laser of claim 24, wherein the third laser beam has a line width narrower than 1 GHz. ### Claim 26 A fiberbased ring laser, comprising: a laser pump a laser gain medium configured to produce a pump laser beam; a laser gain medium configured to produce a first laser beam in response to the pump laser beam; a mode-selection filter configured to receive the first laser beam and to produce a second laser beam that comprises a plurality of spectral peaks having first line widths, wherein two of the plurality of spectral peaks are separated by frequency difference; a first optical fiber configured to transmit the first laser beam from the laser gain medium to the mode-selection filter; a band-pass filter configured to filter the second laser beam and to produce a third laser beam having one of the plurality of spectral peaks, wherein the laser gain medium, the first optical fiber, the mode-selection filter, and the band-pass filter in part form a ring cavity in the fiber-based ring laser; an optical sensor configured to output an output sensing signal in response to the third laser beam; and a controller configured to control the mode-selection filter in response to the output sensing signal to reduce fluctuations in power, frequency, or a combination thereof in the third laser beam; wherein the mode-selection filter comprises: a first reflective plate configured to receive the first laser beam orthogonal to the first reflective plate; an electro-optical material disposed between the first parallel reflective plate, and the second reflective plate; a second reflective plate parallel to the first reflective plate, wherein the first reflective plate, the electro-optical material, and the second reflective plate are configured to filter the first laser beam to produce the second laser beam exiting the second reflection plate; and an electrode configured to apply an electric field in the electro-optical material, the electric field being substantially perpendicular to the first laser beam or the second laser beam. ### Claim 27 (depends on 26) The fiber-based ring laser of claim 26, wherein the optical sensor comprises: an etalon having a free spectral range between about 10 GHz and about 300 GHz and configured to transmit a portion of the third laser beam to produce a first laser sensing signal, and a comparator is configured to produce the output sensing signal by comparing the third laser beam and the first laser sensing signal. ### Claim 28 (depends on 26) The fiber-based ring laser of claim 26, wherein the controller is configured to control the electrode in the mode-selection filter in response to the output sensing signal to reduce fluctuations in power, frequency, or a combination thereof in the third laser beam. ### Claim 29 (depends on 26) The fiber-based ring laser of claim 26, wherein the electric field in the electro-optical material is configured to vary the first wavelength by more than 40 pm for each voltage applied across the electro-optical material. ### Claim 30 (depends on 26) The fiber-based ring laser of claim 26, wherein the electric field in the electro-optical material is configured to tune the one of the plurality of transmission peaks in a frequency range wider than 20 GHz. ### Claim 31 (depends on 26) The fiber-based ring laser of claim 26, wherein the third laser beam has a line width narrower than 150 GHz. ### Claim 32 (depends on 31) The fiber-based ring laser of claim 31, wherein the third laser beam has a line width narrower than 1 GHz.