All-fiber module for femtosecond pulse compression and supercontinuum generation
An all-fiber optical pulse compression arrangement comprises a concatenated arrangement of a section of input fiber (e.g., a single mode fiber), a graded-index (GRIN) fiber lens and a section of pulse-compressing fiber (e.g., LMA fiber). The GRIN fiber lens is used to provide mode matching between the input fiber (supporting the propagation of chirped optical pulses) and the pulse-compressing fiber, with efficient pulse compression occurring along the length of the LMA fiber. The dispersion and length of the LMA fiber section are selected to provide the desired degree of pulse compression; for example, capable of reconstituting a femtosecond pulse as is used in supercontinuum generation systems.
1. An optical pulse compressor comprising:
a first section of fiber exhibiting a first effective area A eff-1 at an operating wavelength, said first section of fiber supporting the propagation of a chirped optical pulse;
a graded-index fiber lens coupled to the output of the first section of fiber, wherein the graded-index fiber lens exhibits an approximately parabolic-shaped graded index profile; and
a second section of fiber exhibiting a second effective area A eff-2 at the operating wavelength, where A eff-2 >A eff-1 , and further exhibiting a dispersion D and a length L selected to compress the chirped optical pulse, said second section of fiber coupled to the output of the graded-index fiber lens, wherein the graded-index fiber lens provides mode matching between said first and second sections of fiber over a bandwidth of greater than 2 nanometers, the bandwidth is defined at full-width half-maximum.
2. An optical pulse compressor as defined in claim 1 wherein the graded-index fiber lens comprises a quarter-pitch fiber lens or any odd multiple thereof.
3. An optical pulse compressor as defined in claim 1 wherein the first section of fiber comprises a section of single mode fiber.
4. An optical pulse compressor as defined in claim 1 wherein the second section of fiber comprises a section of large-mode area (LMA) fiber.
5. An optical pulse compressor as defined in claim 1 wherein the dispersion, D, and length, L, of the second section of fiber are selected to produce a femtosecond optical pulse.
6. An optical pulse compressor as defined in claim 1 wherein the second section of fiber exhibits multi-path interference of less than −15 dB.
7. An optical pulse compressor as defined in claim 1 wherein the input of the graded-index fiber lens is fused to the output of the first section of fiber.
8. An optical pulse compressor as defined in claim 1 wherein the output of the graded-index fiber lens is fused to the input of the second section of fiber.
9. An optical pulse compressor as defined in claim 8 wherein the input of the graded-index fiber lens is fused to the output of the first section of fiber.