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UID:20260522T061748EDT-02201Tb3aL@132.216.98.100
DTSTAMP:20260522T101748Z
DESCRIPTION:Abstract\n\nThe spectral window of the mid-infrared (MIR\, 2-20
  µm) is important for spectroscopy\, sensing\, and optical coherence tomog
 raphy applications. Such emerging applications have intensified research i
 n developing fiber-based MIR light sources using nonlinear wavelength conv
 ersions such as soliton self-frequency shift (SSFS) and supercontinuum gen
 eration (SCG). This thesis explores SSFS and SCG in cascaded nonlinear fib
 ers (NLFs). In the first half of the thesis\, wavelength converters based 
 on SSFS are presented. Chapter 3 presents a soliton order preservation mec
 hanism leading to broad tunability with high energy conversion efficiency 
 (ECE) in a passive fiber-based SSFS. Here\, a pulse compressing fiber\, pl
 aced before a Raman shifting NLF\, acts as a soliton order preserver. Soli
 ton order at the input of the NLF is preserved within 2.0<N<2.3 despite a 
 6.7-fold energy increase. The resulting pulse leads to an SSFS that is spe
 ctrally tunable over 1.96–2.14 µm while keeping an ECE of 80–85%. This is 
 the first time an ECE>80% is maintained over a tunable range as large as 1
 80 nm. In Chapter 4\, SSFS in a cascade involving three types of NLFs made
  of three different glasses\, that is\, silica\, fluoride\, and ChG\, is d
 emonstrated for the first time. Due to high nonlinearity\, incorporating C
 hG NLF in a cascade significantly reduces the pump pulse energy required t
 o achieve a target SSFS\, simplifying the wavelength converter. The disper
 sion and nonlinearity of the NLFs convert a fundamental soliton in one NLF
  to become a high-order soliton in the subsequent NLF\, allowing soliton f
 ission followed by SSFS at each cascade stage. A pump pulse with an energy
  of 10.6 nJ at a wavelength of 1.94 µm is converted to a tunable soliton i
 n the range of 2.09-2.14 µm in the silica NLF\, 2.30-2.52 µm in the ZBLAN 
 NLF\, and 3.05-3.28 µm in the ChG NLF\, resulting in a cumulative waveleng
 th offset of 1340 nm (63.2 THz).\n\nIn the second half of the thesis\, wav
 elength converters based on SCG are presented. Chapter 5 presents the firs
 t all-fiber MIR coherent supercontinuum spanning a spectral range of 1.7-5
 .0 µm from a cascade of silica\, ZBLAN\, and ChG NLFs. Coherence is mainta
 ined across the three NLFs by employing femtosecond pumping and determinis
 tic spectral broadening at each stage of the cascade\, as opposed to the c
 ommonly used nanosecond-picosecond pumping and non-deterministic spectral 
 broadening via noise-seeded modulation instability. Once in the NLF\, the 
 pump pulse is converted into a soliton of order maintained at N<6 in the s
 ilica and the ZBLAN NLFs\, ensuring soliton fission followed by SSFS. Fina
 lly\, in the ChG NLF\, where dispersion is normal\, spectral broadening is
  facilitated through self-phase modulation\, Raman-induced frequency shift
 \, and dispersive wave generation. The deterministic nature of these nonli
 near phenomena results in generating a coherent supercontinuum. Chapter 6 
 demonstrates the widest SCG in the wavelength range of 1.1-3.9 µm from a h
 ybrid microtaper made of an As2S3 core and polycarbonate cladding. The mic
 rotaper is the last stage of a three-stage NLF cascade. In the first stage
 \, made of silica fiber\, a pump pulse at a wavelength of 1.94 µm is conve
 rted to a fundamental soliton at 2.14 µm via SSFS. In the second stage\, m
 ade of ZBLAN fiber\, this soliton experiences further SSFS up to 2.86 µm t
 o become a new pump for the hybrid microtaper. The new pump can access the
  anomalous dispersion in the microtaper with a relatively large core diame
 ter of 4.4 µm compared to the 2.0 µm core diameter required for a 1.94 µm 
 pump. The large core diameter increases modal confinement and reduces tran
 smission loss associated with C-H bonds in the polymer cladding. Additiona
 lly\, a short microtaper length of 2.5 cm further mitigates the effect of 
 C-H induced loss\, and a cladding diameter of 270 µm provides mechanical s
 trength to the microtaper.\n
DTSTART:20241031T170000Z
DTEND:20241031T190000Z
LOCATION:Room 603\, McConnell Engineering Building\, CA\, QC\, Montreal\, H
 3A 0E9\, 3480 rue University
SUMMARY:PhD defence of Md Hosne Mobarok Shamim – Mid-infrared soliton self-
 frequency shift and supercontinuum generation in cascaded nonlinear fibers
URL:/ece/channels/event/phd-defence-md-hosne-mobarok-s
 hamim-mid-infrared-soliton-self-frequency-shift-and-supercontinuum-360650
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