READ ME File for 'Fibre Raman Amplification of Bessel and Orbital Angular Momentum Higher Order Modes in Step Index Fibres'

Dataset DOI: https://doi.org/10.5258/SOTON/D1912

Readme Author: Sheng Zhu, University of Southampton, ORCID: https://orcid.org/0000-0002-4256-6307

This dataset supports doctoral thesis:

Fibre Raman Amplification of Bessel and Orbital Angular Momentum Higher Order Modes in Step Index Fibres


Contents
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This dataset contains which are used for generating the following figures:

Figure 3.1: Comparisons of power and gain in the YDFA and the FRA in the incoherent simulations.	
Figure 3.2: Mode purity of the target HOM in the incoherent FRA (red curves) and YDFA (black curves) plotted against (a) normalized distance and (b) normalized signal power.	
Figure 3.3: Intensity distributions normalized to the maximum value of the respective curves in the radial direction across the centre of the fibre core in the incoherent FRA and YDFA.
Figure 3.4: Comparison of the mode purity of a sample FRA with different mode field amplitudes.
Figure 3.5: Comparisons of power and gain in the YDFA and the FRA in the coherent simulations.	
Figure 3.6: Mode purity of the target HOM in the coherent FRA (red curves) and YDFA (black curves) plotted against (a) normalized distance and (b) normalized signal power.	
Figure 3.7: (a) Mode purity of the target HOM in the coherent YDFA and FRA with different core radii against the core NA. (b) Mode purity of the YDFA and FRA from (a) plotted against the number of signal modes supported in the fibre.	
Figure 4.3: Spectrum of the 1060-nm pump beam from YDFA at ~18 kW output peak power.	
Figure 4.4: Measured average power gain and weighted pump depletion versus launched peak pump power.	
Figure 4.5: (a) Pump pulse at input and output of Raman gain fibre at 18 dB signal gain. The output signal is also shown but temporally shifted. Dashed line shows temporally overlapped region between pump and signal pulses. (b) Signal pulse at input and output of Raman gain fibre at 16 dB gain. Scales are different for input (left) and output.	
Figure 4.6: Transmitted 1060-nm pulse from YDFA without 970-nm pump.	
Figure 4.7: Measured spectra of amplified signal at different gain levels.	
Figure 4.8: Transverse intensity distributions and line profiles of the signal output beams.	
Figure 4.12: Measured refractive index profile of the Raman gain fibre with a 50-µm diameter core.	
Figure 4.15: Measured average power gain and weighted pump depletion (right scale) versus launched pump peak power.	
Figure 4.16: Measured spectra of the output signal.	
Figure 4.17: (a) Transmitted pump pulses at 25 dB gain level with (black curve) and without (red curve) Raman seed. (b) Transmitted signal pulses without pumping (black curve) and amplified signal (red curve).	
Figure 4.18: Intensity profiles of output signal at 0 dB gain (a) and 25 dB gain (b) with greyscale in log scale and normalized. (c) Line profiles across the centre of the beam at 0 dB and 25 dB gain in log scale.	
Figure 4.20: Spectrum of FBG stabilized diode.	
Figure 4.24: Average power gain of signal (black curve, left scale) and weighted pump depletion (blue curve, right scale) versus launched pump peak power.	
Figure 4.25: (a) Measured spectra of output signal. (b) Zoomed in spectra.	
Figure 4.26: (a) Transmitted pump pulse at 23 dB gain with Raman seed (blue curve) and the same pump level but without seed (black curve). Incident pump shown in dashed curve, with shifted time and different scaling. (b) Incident (dashed curve) and transmitted signal pulses at 0 dB (black curve) and 23 dB (blue curve) gain. Traces scaled to same height.	
Figure 4.27: Pump depletion (black curve) and transmitted signal (red curve) at 23 dB gain.	
Figure 4.28: Intensity profiles of output signal beams at (a) 0 dB, (b) 23 dB, (c) 25 dB in log scale and normalized. (d) Normalized line profiles in log scale across the centre of the signal beams at selected gain levels.	
Figure 4.29: Intensity profiles of output pump beam with (left) and without (right) Raman seed at 23 dB (a) and 25 dB (b) gain. Line profiles of output pump beam (left scale) and transverse pump depletion (right scale) at 23 dB (c) and 25 dB (c) gain.	
Figure 4.31: Spectra of combined pump from diode lasers at full power.	
Figure 4.32: (a) Measured average power on-off gain versus total launched pump peak power. The labels show the power at which each diode laser is turned. (b) Measured spectra of output signal beam. Different curves correspond to maximum pump power before the next shorter-wavelength diode laser is turned on in (a) (e.g., +969 nm means that the 976-nm and 969-nm diode lasers are both at full power whereas the others are off).	
Figure 4.33: (a) Transmitted signal with no pumping and at maximum output of each diode laser. (b) Scattered pump at the maximum power of each diode laser.	
Figure 4.34: Intensity profiles of transmitted signal in log scale at (a) 0 dB and (b) 6 dB gain. (c) Line profiles across the centre of the beam at two gain level. Intensity plotted in log scale.	
Figure 5.2: Measured refractive index profile of the OFS Raman gain fibre.	
Figure 5.4: Measured average power gain of the signal (left scale) and the pump depletion (right scale) versus launched pump peak power.	
Figure 5.5: Measured optical spectra of the output signal at different gain levels.	
Figure 5.6: Measured temporal traces of the incident pump (red curve) and signal (black curve) as well as the amplified signal at 15 dB gain (orange curve).	
Figure 5.9: (a) Fraction of power in the output signal versus charges from -4 to +4 for 0 dB and 15 dB gain. (b) Mode purity of l = +2 OAMM and the fraction of power in l = -2 versus the Raman gain.	
Figure 5.12: (a) Effective index separation between the quasi-degenerate HE and EH modes versus charge number l. (b) Effective index separation between the OAMM and its nearest neighbour mode versus charge number.	
Figure 5.15: Measured average power gain versus launched pump peak power.	
Figure 5.16: (a) Optical spectra of the transmitted signal at 0 dB gain (black), at 9.2 dB gain (green), and the transmitted light with pumping but no Raman seed (red). (b) Zoomed-in spectra of the transmitted signal with and without amplification.	
Figure 5.17: Temporal traces of the transmitted signal pulse without pumping (black curve), at 9.2 dB gain (blue curve) and the leaked pump pulse (orange curve). Launched pump pulse at 9.2 dB gain level is also plotted (red curve) with a different scale.	
Figure 5.20: Fraction of power of the transmitted signal in different charges for 0 dB and 9.2 dB gain.	

Geographic location of data collection: University of Southampton, U.K.

Related projects:
Fundamental Laser Science for High Powers
Fibres & Pulse Combination
Study of orbital angular momentum mode fibre amplification of optical pulses

Dataset available under a CC BY licence


Publisher: University of Southampton, U.K.

Date of data producation: Oct 1 2016- Dec 31 2020


Date: Aug 4 2021