Giant-chirp oscillator

Abstract

A laser apparatus operable to generate giant chirp pulses. The pulses have a centre frequency comprising an arrangement of components connected or connectable to form a closed ring cavity. The components comprise a first gain medium, an optical isolator, a length of single mode fibre, a mode locking device, an output coupler, and an optical filter. Each of the components are optical fibre based components.

1 - 32 . (canceled) 
     
     
         33 . A laser apparatus operable to generate giant chirp pulses having a center frequency, comprising an arrangement of components connected, or connectable to form a cavity, the components comprising a first gain medium, an optical isolator, a length of single mode fibre, a passive mode locking device, an output coupler, and an optical filter, wherein each of the components are optical fibre based components. 
     
     
         34 . A laser as claimed in  claim 33 , wherein the optical fibre components are polarization maintaining components. 
     
     
         35 . A laser as claimed in  claim 33 , wherein the components have, or substantially have, a normal dispersion relative to the center frequency. 
     
     
         36 . A laser as claimed in  claim 33 , wherein the components have a net normal dispersion relative to the center frequency. 
     
     
         37 . A laser as claimed in  claim 33 , wherein the mode locking device is a nonlinear amplified loop mirror comprising at least an optical coupler operable to provide and input and an output, and a second gain medium operable to provide energy to a propagating pulse. 
     
     
         38 . A laser as claimed in  claim 33 , wherein the mode locking device is operable to mode lock the laser by varying the energy of the light from the second pump source. 
     
     
         39 . A laser as claimed in  claim 33 , wherein the length of single mode fibre is operable in the cavity to receive light from the first gain medium and output light to the second gain medium. 
     
     
         40 . A laser as claimed in  claim 33 , wherein the length of single mode fibre is operable to impart broadening to a pulse propagating within it. 
     
     
         41 . A laser as claimed in  claim 33 , wherein the laser is operable to generate giant chirp pulses comprising a chirp that is substantially linear and positive. 
     
     
         42 . A laser as claimed in  claim 33 , wherein varying the length of the single mode fibre varies at least one or more of the pulse repetition rate, the pulse energy or the pulse duration. 
     
     
         43 . A laser as claimed in  claim 33 , wherein the optical filter has an operating bandwidth centered at or approximately at a desired pulse wavelength. 
     
     
         44 . A laser operable as a giant chirp oscillator, comprising a loop of substantially polarization maintaining, substantially normal dispersion, optical fibre based components including a gain medium, a section of single mode fibre, and an nonlinear amplifying optical loop mirror. 
     
     
         45 . A laser operable as a giant chirp oscillator, comprising:
 a first lasing section comprising all normal dispersion optical components and a second lasing section comprising a nonlinear amplifying loop mirror, wherein the first and second lasing sections are operable to generate giant chirp pulses.   
     
     
         46 . A laser as claimed in  claim 45  wherein the first and second lasing sections each comprise a loop of polarization maintaining, all normal dispersion optical fibre, wherein a first loop comprises a polarization maintaining normal dispersion first gain medium, a polarization maintaining normal dispersion optical filter, a polarization maintaining normal dispersion optical isolator, and a length of polarization maintaining normal dispersion single mode fibre, and a second loop comprises a polarization maintaining normal dispersion second gain medium, and the first loop is optically coupled to the second loop by a wavelength division multiplexing optical coupler. 
     
     
         47 . A laser as claimed in  claim 46  wherein the first loop further comprises wavelength division multiplexing optical coupler to couple a source of pump light into the first gain medium, the second loop further comprises wavelength division multiplexing optical coupler to couple a source of pump light into the second gain medium, and at least one of the sources of pump light are operable to mode lock the oscillator.