# US 9,438,006 B2 · Compact Raman generators > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,006 B2 - Document ID: US9438006B2 - Status: Granted - Kind: B2 - Application number: 13/476,687 - Filed: 2012-05-21 - Published: 2013-11-21 - Granted: 2016-09-06 - Earliest claimed: 2012-05-21 - Assignees: Raytheon Company - Applicants: David A. Rockwell; Vladimir V. Shkunov - Inventors: David A. Rockwell; Vladimir V. Shkunov - Web page: https://patentgrep.com/patent/US9438006B2 ## CPC - H01S 3/30: using scattering effects, e.g. stimulated Brillouin or Raman effects - H01S 3/083: Ring lasers {(fibre ring lasers H01S3/06791)} - H01S 3/094026: {for synchronously pumping, e.g. for mode locking} - H01S 3/2325: {Multi-pass amplifiers, e.g. regenerative amplifiers} - 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 According to an embodiment of the disclosure, a Raman generator includes a Raman medium and one or more optical elements. The Raman medium is configured to receive a pump pulse at a first wavelength and shift at least a portion of the pump pulse energy or power into a Stokes-shifted pulse at a second wavelength. The one or more optical elements are configured to pass the pump pulse and the Stokes-shifted pulse multiple times through the Raman medium. Each pass of the pulses through the Raman medium follows a path. Each path is parallel or anti-parallel to the other paths. ## Claims ### Claim 1 A Raman generator comprising: a Raman medium configured to receive a pump pulse at a first wavelength and shift at least a portion of the pump pulse energy or power into a Stokes-shifted pulse at a second wavelength, the Raman medium having a longitudinal central axis; and one or more optical elements configured to pass the pump pulse and the Stokes-shifted pulse multiple times through the Raman medium; wherein each pass of the pulses through the Raman medium follows a path; wherein each path is parallel or anti-parallel to the other paths; and wherein the paths of three or more consecutive passes of the pulses through the Raman medium alternate between opposite sides of the longitudinal central axis of the Raman medium. ### Claim 2 (depends on 1) The Raman generator of claim 1, wherein for each pass through the Raman medium, at least a portion of the pump pulse energy or power is shifted into the Stokes-shifted pulse at the second wavelength; and the one or more optical elements are configured to pass both the pump pulse and the Stokes-shifted pulse along multiple common paths through the Raman medium, the multiple passes increasing a power of the Stokes-shifted pulse. ### Claim 3 (depends on 1) The Raman generator of claim 1, further comprising: at least two lenses configured to limit diffractive spreading of the pump pulse and the Stoke-shifted pulse. ### Claim 4 (depends on 1) The Raman generator of claim 1, wherein the one or more optical elements comprise two prisms of different size. ### Claim 5 (depends on 1) The Raman generator of claim 1, further comprising two lenses and two prism-lens combinations, wherein: prism portions of the prism-lens combinations are configured to pass both the pump pulse and the Stokes-shifted pulse more than two times through the Raman medium, and lens portions of the prism-lens combinations and the two lenses are configured to limit diffractive spreading of the pump and Stokes-shifted pulse. ### Claim 6 (depends on 1) The Raman generator of claim 1, wherein the Raman generator provides an optical length of one meter in a package having a maximum dimension of thirty centimeters. ### Claim 7 (depends on 1) The Raman generator of claim 1, wherein the received pulse is configured to pass through the Raman medium nine times. ### Claim 8 (depends on 1) The Raman generator of claim 1, further comprising a spectral filter configured to control a spectral width of the Stokes-shifted pulse. ### Claim 9 (depends on 1) The Raman generator of claim 1, wherein the Raman generator is configured such that the optical path and polarizations of the pump pulse and Stokes-shifted pulse are matched to preferred crystal axes in the Raman medium. ### Claim 10 (depends on 1) The Raman generator of claim 1, wherein a conversion efficiency of the Raman generator determined by comparing the pump pulse initially received at the first wavelength to the generated Stokes-shifted pulse at the second wavelength is greater than or equal to fifty percent. ### Claim 11 A method for a Raman generator, the method comprising: passing a pump pulse through a Raman medium having a longitudinal central axis a plurality of times, each pass shifting at least a portion of the pump pulse energy or power into a Stokes-shifted pulse at a second wavelength; and passing the Stokes-shifted pulse through the Raman medium a plurality of times to increase a power of the Stokes-shifted pulse; wherein each pass of the pulses through the Raman medium follows a path; wherein each path is one of parallel or anti-parallel to the other paths; and wherein the paths of three or more consecutive passes of the pulses through the Raman medium alternate between opposite sides of the longitudinal central axis of the Raman medium. ### Claim 12 (depends on 11) The method of claim 11, wherein passing the pulses through the Raman medium a plurality of times further comprises: passing the pulses along multiple common paths through the Raman medium to increase a power of the Stokes-shifted pulse. ### Claim 13 (depends on 11) The method of claim 11, wherein the conversion efficiency of a Raman generator performing the method determined by comparing the pump pulse initially received at the first wavelength to the generated Stokes-shifted pulse at the second wavelength after several passes through the Raman medium is greater than or equal to fifty percent. ### Claim 14 (depends on 11) The method of claim 11, further comprising: limiting diffractive spreading of the pump pulse and the Stoke-shifted pulse. ### Claim 15 (depends on 11) The method of claim 11, wherein the passing of the pump pulse and the Stokes-shifted pulse through the Raman medium a plurality of times is carried out with two prisms of different size. ### Claim 16 (depends on 11) The method of claim 11, wherein the pump pulse and the Stokes-shifted pulse are passed through two lenses and two prism-lens combinations, a prism portion of the prism-lens combinations passing both the pump pulse and the Stokes-shifted pulse more than two times through the Raman medium, and a lens portion of the prism-lens combinations and the two lenses limiting the diffractive spreading of the pump and Stokes-shifted pulse. ### Claim 17 (depends on 11) The method of claim 11, wherein the Raman generator is configured such that the optical path and polarizations of the pump pulse and Stokes-shifted pulse are matched to preferred crystal axes in the Raman medium. ### Claim 18 (depends on 11) The method of claim 11, wherein the Raman generator provides an optical length of one meter in a package having a maximum dimension of thirty centimeters. ### Claim 19 (depends on 11) The method of claim 11, wherein the pump pulse and the Stokes-shifted pulse are passed through the Raman medium at least nine times. ### Claim 20 (depends on 11) The method of claim 11, further comprising: limiting a frequency spread of the Stokes-shifted beam relative to the frequency of the pump pulse. ### Claim 21 (depends on 1) The Raman generator of claim 1, wherein the longitudinal central axis of the Raman medium denotes a longest dimension of the Raman medium.