# US 5,708,669 A · Article comprising a cladding-pumped optical fiber laser > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,708,669 A - Document ID: US5708669A - Status: Granted - Kind: A - Application number: 08/719,278 - Filed: 1996-09-24 - Granted: 1998-01-13 - Earliest claimed: 1996-09-24 - Assignees: Lucent Technologies Inc. - Inventors: David John DiGiovanni; Ashish Madhukar Vengsarkar - Web page: https://patentgrep.com/patent/US5708669A ## CPC - H01S 3/094003: {the pumped medium being a fibre} - H01S 3/06708: {Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering (optical fibres as passive waveguides G02B6/02)} - H01S 3/0675: {Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers} - H01S 3/06729: {Peculiar transverse fibre profile} - H01S 3/094007: {Cladding pumping, i.e. pump light propagating in a clad surrounding the active core} - 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 cladding pumped optical fiber laser comprises a length of optical fiber having a rare earth-doped region of diameter d.sub.RE >d.sub.01 where d.sub.01 is the mode diameter of the LP.sub.01 mode of the fiber at the laser radiation at wavelength .lambda.. In one embodiment the fiber has a core diameter d.sub.c selected such that the LP.sub.01 mode is the only guided spatial mode of the fiber, and d.sub.RE is greater than d.sub.c. In another embodiment the fiber supports at least one higher order guided spatial mode, typically LP.sub.11 or LP.sub.02, and d.sub.RE is approximately equal to or larger than d.sub.c. Currently preferred embodiments comprise a grating-defined laser cavity that comprises a mode-coupling refractive index grating. Cladding pumped lasers according to the invention will typically have efficient conversion of pump radiation to laser radiation, and consequently can typically be shorter than analogous prior art cladding pumped lasers. ## Claims ### Claim 1 An article comprising a first cladding pumped fiber laser comprising a length of optical fiber having an essentially circularly symmetric core of relatively large refractive index contactingly surrounded by a cladding of relatively low refractive index, said core having a diameter d.sub.c selected such that said optical fiber supports a fundamental guided spatial mode LP.sub.01 of laser radiation of wavelength .lambda., said LP.sub.01 mode having an effective mode diameter d.sub.01, said core comprising a rare earth dopant selected to emit said laser radiation in said optical fiber; CHARACTERIZED IN THAT said rare earth dopant is distributed throughout a portion of the optical fiber that comprises said core, said portion having a diameter d.sub.RE >d.sub.01. ### Claim 2 (depends on 1) Article according to claim 1, wherein d.sub.c is selected such that the LP.sub.01 mode is the only guided mode supported by the optical fiber, and wherein d.sub.RE >d.sub.c. ### Claim 3 (depends on 1) Article according to claim 1, wherein d.sub.c is selected such that the optical fiber supports at least one higher order guided spatial mode of the radiation of wavelength .lambda., wherein d.sub.RE is approximately equal to or larger than d.sub.c. ### Claim 4 (depends on 3) Article according to claim 3, wherein said optical fiber comprises refractive index gratings that define a laser cavity, with the laser cavity comprising at least one mode-coupling refractive index grating. ### Claim 5 (depends on 4) Article according to claim 4, wherein the at least one mode-coupling refractive index grating is disposed within said laser cavity. ### Claim 6 (depends on 5) Article according to claim 5, wherein the mode-coupling refractive index grating is selected to transmit a fraction x of incident LP.sub.01 radiation of wavelength .lambda. as LP.sub.01 radiation, and to reflect a fraction substantially equal to (1-x) of said incident LP.sub.01 radiation as higher order mode radiation of wavelength .lambda.. ### Claim 7 (depends on 4) Article according to claim 4, wherein the at least one mode-coupling refractive index grating serves to define said laser cavity. ### Claim 8 (depends on 7) Article according to claim 7, wherein the at least one higher order guided spatial mode is LP.sub.11 and wherein the at least one mode-coupling refractive index grating is selected to reflect essentially all LP.sub.11 radiation of wavelength .lambda. incident on the grating as LP.sub.01 radiation. ### Claim 9 (depends on 7) Article according to claim 7, wherein the at least one higher order guided spatial mode is LP.sub.02, and wherein the at least one mode-coupling refractive index grating is selected to reflect essentially all LP.sub.02 radiation of wavelength .lambda. incident on the grating as LP.sub.01 radiation. ### Claim 10 (depends on 1) Article according to claim 1, wherein said length of optical fiber is less than 100 m. ### Claim 11 (depends on 1) Article according to claim 1, wherein the article is an optical fiber communication system comprising a transmitter, a receiver, and an optical fiber transmission path signal transmissively connecting said transmitter and receiver, wherein said first cladding pumped fiber laser is optically coupled to said optical fiber transmission path such that said laser radiation is available for utilization in the optical fiber transmission path. ### Claim 12 (depends on 11) Article according to claim 11, wherein said optical fiber transmission path comprises an optical fiber amplifier, and wherein said radiation serves as pump radiation in the optical fiber amplifier. ### Claim 13 (depends on 11) Article according to claim 11, the article further comprising a second cladding pumped fiber laser, and still further comprising means for combining the output radiation of the first and the second cladding pumped fiber lasers.