TY  - JOUR
A1  - Zajnulina, Marina
A1  - Boggio, Jose M. Chavez
A1  - Böhm, Michael
A1  - Rieznik, A. A.
A1  - Fremberg, Tino
A1  - Haynes, Roger
A1  - Roth, Martin M.
T1  - Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy
JF  - Applied physics : B, Lasers and optics
N2  - We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrodinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.
Y1  - 2015
U6  - https://doi.org/10.1007/s00340-015-6121-1
SN  - 0946-2171
SN  - 1432-0649
VL  - 120
IS  - 1
SP  - 171
EP  - 184
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Zajnulina, Marina
A1  - Böhm, Michael
A1  - Blow, K.
A1  - Rieznik, A. A.
A1  - Giannone, Domenico
A1  - Haynes, Roger
A1  - Roth, Martin M.
T1  - Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4930316
SN  - 1054-1500
SN  - 1089-7682
VL  - 25
IS  - 10
PB  - American Institute of Physics
CY  - Melville
ER  -