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Polarisation dynamics of vector soliton molecules in mode locked fibre laser.

Tsatourian V, Sergeyev SV, Mou C, Rozhin A, Mikhailov V, Rabin B, Westbrook PS, Turitsyn SK - Sci Rep (2013)

Bottom Line: Two fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity.Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications.Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing.

View Article: PubMed Central - PubMed

Affiliation: 1] Aston Institute of Photonic Technologies, School of Engineering & Applied Science Aston University, Birmingham, B4 7ET, UK [2] National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK [3] School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.

ABSTRACT
Two fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity. Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications. Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing. The underlying physics presents an interplay between linear and circular birefringence of a laser cavity along with light induced anisotropy caused by polarisation hole burning.

No MeSH data available.


Related in: MedlinePlus

Polarisation dynamics of bound state soliton in the form of superposition pfpolarisation switching between two SOPs of two interleaved BSs and SOP precession.(a) Output optical spectrum indicates interleaved BSs with phase shifts of π/2 and π, 740 fs pulse width and 1.5 ps pulse separation; inset: pulse train of harmonically mode locked operation with period of 20 ns collected from four polarimeter photodetectors; (b) total optical power (red squares) and DOP (black circles); (d) Stokes parameters on the Poincaré sphere. Each point in Fig. (b)–(d) corresponds to a single laser pulse.
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f6: Polarisation dynamics of bound state soliton in the form of superposition pfpolarisation switching between two SOPs of two interleaved BSs and SOP precession.(a) Output optical spectrum indicates interleaved BSs with phase shifts of π/2 and π, 740 fs pulse width and 1.5 ps pulse separation; inset: pulse train of harmonically mode locked operation with period of 20 ns collected from four polarimeter photodetectors; (b) total optical power (red squares) and DOP (black circles); (d) Stokes parameters on the Poincaré sphere. Each point in Fig. (b)–(d) corresponds to a single laser pulse.

Mentions: The ring cavity fibre laser (total cavity length of 7.83 m) shown in Fig. 2 includes high concentration erbium doped fibre (2 m of LIEKKI™ Er80-8/125), single mode (SM) fibre with anomalous dispersion, polarisation controllers (POCs), a wavelength division multiplexing (WDM) coupler, an optical isolator (OISO), a fast (370 fs relaxation time) saturable absorber in the form of carbon nanotubes (CNT) doped polymer film, and an output coupler. The cavity is pumped via 980/1550 WDM by a 976 nm laser diode (LD) with a maximum current of about 355 mA which provides 170 mW of optical power3334. The laser output is analysed with the help of the optical spectrum analyser (ANDO AQ6317B) and the inline polarimeter (OFS TruePhase IPLM with resolution of 2 ns and the number of samples was 10 M)5152. IPLM measured the normalized Stokes parameters s1, s2, s3 and degree of polarization (DOP) which are related to the output powers of two linearly cross-polarized SOPs and , and phase difference between them Δφ as follows: optimised for the high-speed operation; for further details see below in Methods. In this experiment, pump current was about 300 mA, and the in-cavity and pump polarisation controllers have been tuned to obtain the polarisation attractors shown in Figs. 3,4,5,6. Fig. 3(a) shows a spectrum of tightly two-pulse bound state soliton with phase shift of π according to Fig. 1 (b). The corresponding pulse train with the period of 38.9 ns is collected from four polarimeter detectors is shown in insert to Fig. 3 (a). The polarisation dynamics shown in Fig. 3(b–d) take the form of polarisation switching between two SOPs with period equal to two pulse round trips in the laser cavity. DOP oscillations around the value of 90% have also been observed (Fig. 3 (b)). In view of detector integration time (2 ns) being longer than the pulse separation (2 ps), high value of DOP indicates that bound solitons have the same SOP otherwise DOP will be close to zero for the case of orthogonal SOPs. The total laser power (S0 in Fig. 3(b)) is constant within ±5% precision. Pulse width and pulse separation have been found from Fig. 3 (a) as 370 fs and 1.5 ps. Contrast of spectral fringes in Fig. 3 (a) is high and the pulse separation is less than five pulse widths, therefore BS is a tightly bound soliton with fixed phase shift and pulse separation789101112131415161718. Fig. 4 shows the other type of polarisation dynamics of bound state soliton. The spectrum in Fig. 4 (a) is similar to the previous one shown in Fig. 3(a) and so BS is a tightly bound soliton with fixed phase shift of π and pulse separation of 1.5 ps789101112131415161718. In this case, the variations of the total laser power were less than 5% (Fig. 4 (b)). DOP oscillates around the value of 80% with the period equal to three cavity round trips (Fig. 4 (b)). Stokes parameters s1, s2, s3 oscillate with the lowest, intermediate and highest values corresponding to each of the localized SOPs shown in Fig. 4 (d). Spectra in Figs. 3 (a) and 4 (a) demonstrate the presence of slight asymmetry. It can be caused by hopping between π- and −π/2-shifted bound states that arises from changing the erbium gain spectrum under long-term fluctuations of ambient temperature18. High contrast of spectral fringes and small asymmetry of spectrum indicates that lifetime in π-shifted BS is much longer than lifetime in −π/2-shifted BS. Otherwise, the spectrum takes the form shown in Fig. 5 (a), i.e. it is close to the −π/2-shifted tightly BS with pulse width of 370 fs and pulse separation of 1.5 ps. Output power and DOP oscillations with two periods of 3 and 20 round trips as shown in Fig. 5 (b). SOP evolution takes the form of superposition of switching between three SOPs with a precession of these SOPs along a circle trajectory located on Poincaré sphere with the periods of 3 and 20 round trips (Fig. 5 (c, d)).


Polarisation dynamics of vector soliton molecules in mode locked fibre laser.

Tsatourian V, Sergeyev SV, Mou C, Rozhin A, Mikhailov V, Rabin B, Westbrook PS, Turitsyn SK - Sci Rep (2013)

Polarisation dynamics of bound state soliton in the form of superposition pfpolarisation switching between two SOPs of two interleaved BSs and SOP precession.(a) Output optical spectrum indicates interleaved BSs with phase shifts of π/2 and π, 740 fs pulse width and 1.5 ps pulse separation; inset: pulse train of harmonically mode locked operation with period of 20 ns collected from four polarimeter photodetectors; (b) total optical power (red squares) and DOP (black circles); (d) Stokes parameters on the Poincaré sphere. Each point in Fig. (b)–(d) corresponds to a single laser pulse.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3818655&req=5

f6: Polarisation dynamics of bound state soliton in the form of superposition pfpolarisation switching between two SOPs of two interleaved BSs and SOP precession.(a) Output optical spectrum indicates interleaved BSs with phase shifts of π/2 and π, 740 fs pulse width and 1.5 ps pulse separation; inset: pulse train of harmonically mode locked operation with period of 20 ns collected from four polarimeter photodetectors; (b) total optical power (red squares) and DOP (black circles); (d) Stokes parameters on the Poincaré sphere. Each point in Fig. (b)–(d) corresponds to a single laser pulse.
Mentions: The ring cavity fibre laser (total cavity length of 7.83 m) shown in Fig. 2 includes high concentration erbium doped fibre (2 m of LIEKKI™ Er80-8/125), single mode (SM) fibre with anomalous dispersion, polarisation controllers (POCs), a wavelength division multiplexing (WDM) coupler, an optical isolator (OISO), a fast (370 fs relaxation time) saturable absorber in the form of carbon nanotubes (CNT) doped polymer film, and an output coupler. The cavity is pumped via 980/1550 WDM by a 976 nm laser diode (LD) with a maximum current of about 355 mA which provides 170 mW of optical power3334. The laser output is analysed with the help of the optical spectrum analyser (ANDO AQ6317B) and the inline polarimeter (OFS TruePhase IPLM with resolution of 2 ns and the number of samples was 10 M)5152. IPLM measured the normalized Stokes parameters s1, s2, s3 and degree of polarization (DOP) which are related to the output powers of two linearly cross-polarized SOPs and , and phase difference between them Δφ as follows: optimised for the high-speed operation; for further details see below in Methods. In this experiment, pump current was about 300 mA, and the in-cavity and pump polarisation controllers have been tuned to obtain the polarisation attractors shown in Figs. 3,4,5,6. Fig. 3(a) shows a spectrum of tightly two-pulse bound state soliton with phase shift of π according to Fig. 1 (b). The corresponding pulse train with the period of 38.9 ns is collected from four polarimeter detectors is shown in insert to Fig. 3 (a). The polarisation dynamics shown in Fig. 3(b–d) take the form of polarisation switching between two SOPs with period equal to two pulse round trips in the laser cavity. DOP oscillations around the value of 90% have also been observed (Fig. 3 (b)). In view of detector integration time (2 ns) being longer than the pulse separation (2 ps), high value of DOP indicates that bound solitons have the same SOP otherwise DOP will be close to zero for the case of orthogonal SOPs. The total laser power (S0 in Fig. 3(b)) is constant within ±5% precision. Pulse width and pulse separation have been found from Fig. 3 (a) as 370 fs and 1.5 ps. Contrast of spectral fringes in Fig. 3 (a) is high and the pulse separation is less than five pulse widths, therefore BS is a tightly bound soliton with fixed phase shift and pulse separation789101112131415161718. Fig. 4 shows the other type of polarisation dynamics of bound state soliton. The spectrum in Fig. 4 (a) is similar to the previous one shown in Fig. 3(a) and so BS is a tightly bound soliton with fixed phase shift of π and pulse separation of 1.5 ps789101112131415161718. In this case, the variations of the total laser power were less than 5% (Fig. 4 (b)). DOP oscillates around the value of 80% with the period equal to three cavity round trips (Fig. 4 (b)). Stokes parameters s1, s2, s3 oscillate with the lowest, intermediate and highest values corresponding to each of the localized SOPs shown in Fig. 4 (d). Spectra in Figs. 3 (a) and 4 (a) demonstrate the presence of slight asymmetry. It can be caused by hopping between π- and −π/2-shifted bound states that arises from changing the erbium gain spectrum under long-term fluctuations of ambient temperature18. High contrast of spectral fringes and small asymmetry of spectrum indicates that lifetime in π-shifted BS is much longer than lifetime in −π/2-shifted BS. Otherwise, the spectrum takes the form shown in Fig. 5 (a), i.e. it is close to the −π/2-shifted tightly BS with pulse width of 370 fs and pulse separation of 1.5 ps. Output power and DOP oscillations with two periods of 3 and 20 round trips as shown in Fig. 5 (b). SOP evolution takes the form of superposition of switching between three SOPs with a precession of these SOPs along a circle trajectory located on Poincaré sphere with the periods of 3 and 20 round trips (Fig. 5 (c, d)).

Bottom Line: Two fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity.Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications.Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing.

View Article: PubMed Central - PubMed

Affiliation: 1] Aston Institute of Photonic Technologies, School of Engineering & Applied Science Aston University, Birmingham, B4 7ET, UK [2] National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK [3] School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.

ABSTRACT
Two fundamental laser physics phenomena--dissipative soliton and polarisation of light are recently merged to the concept of vector dissipative soliton (VDS), viz. train of short pulses with specific state of polarisation (SOP) and shape defined by an interplay between anisotropy, gain/loss, dispersion, and nonlinearity. Emergence of VDSs is both of the fundamental scientific interest and is also a promising technique for control of dynamic SOPs important for numerous applications from nano-optics to high capacity fibre optic communications. Using specially designed and developed fast polarimeter, we present here the first experimental results on SOP evolution of vector soliton molecules with periodic polarisation switching between two and three SOPs and superposition of polarisation switching with SOP precessing. The underlying physics presents an interplay between linear and circular birefringence of a laser cavity along with light induced anisotropy caused by polarisation hole burning.

No MeSH data available.


Related in: MedlinePlus